Low relative resting metabolic rate and body weight gain in adult Caucasian Italians

Resting metabolic rate in obesity

The prevalence of obesity has continued to rise, and obesity and its attendant metabolic disorders are major global health threat factors. Among the current interventions for obesity, none have demonstrated sustained efficacy in achieving long-term outcomes. So, the identification of therapeutic targets is of paramount importance in the advancement and sustainability of obesity. Resting metabolic rate (RMR) constitutes 60%-75% of total energy expenditure and serves a crucial function in maintaining energy balance. Nevertheless, there exists considerable heterogeneity in RMR among individuals. Low RMR is associated with weight gain, elevating the susceptibility to obesity-related ailments. Hence, RMR will be the main focus of interest in the study of obesity treatment. In this review, we will elucidate the influence factors and mechanisms of action of RMR in obesity, with particular emphasis on the effects of obesity treatment on RMR and the alterations and influence factors of RMR in special types of populations with obesity.

Comparison of central obesity prevalence among adults living with and without HIV in Botswana: a cross-sectional study

OBJECTIVES

The aim was to establish the community prevalence of central obesity in Botswana and assess its association with HIV status.

DESIGN

We performed a one-time central obesity assessment nested within a community-based cluster-randomised controlled HIV treatment and prevention trial (Botswana Combination Prevention Project (BCPP)) conducted in Botswana.

SETTING

The BCPP enrolled consenting adults from a random sample of 20% of households in 30 rural/peri-urban communities.

PARTICIPANTS

A subset of participants from 22 communities was selected for a nested central obesity study.

PRIMARY AND SECONDARY OUTCOME MEASURES

Central obesity was defined as a waist-to-hip ratio (WHR)>0.90 for males and >0.85 for females or as a waist circumference (WC) ≥94 cm for males and ≥80 cm for females. A modified Poisson regression model was used to ascertain the association between central obesity and HIV status. Additionally, the same model was used to estimate the adjusted prevalence ratio (aPR) for central obesity among participants with missing waist and hip measurements by applying inverse probability weighting, and then adjusting for sex and age in the final multivariate models.

RESULTS

Of the 3981 adults, 2039 (51%) completed central obesity assessment (67% female, 29% people living with HIV and median age 35.4 years (IQR 26.4-48.3 years). Central obesity prevalence was 43.5% (95% CI 41.4% to 45.7%) and 50.8% (95% CI 48.6% to 52.9%) as defined by WHR and WC, respectively, and was higher among females than males by WHR (46.9% (95% CI 44.2% to 49.5%) vs 36.7% (95% CI 33.1% to 40.4%)) and WC 68.5% ((95% CI 65.9% to 70.9%) vs 15.1% (95% CI 12.4% to 17.8%)) and increased with age. In fully adjusted models, there was no difference in central obesity by HIV status for both WHR and WC, aPR 0.99 (95% CI 0.90 to 1.09), p value 0.88, and 0.93 (95% CI 0.85 to 1.01), p value 0.06, respectively.

CONCLUSION

Over two-thirds of adult females in Botswana had central obesity; however, living with HIV was not consistently associated with central obesity.

TRIAL REGISTERATION NUMBER

NCT01965470.

Divergent selection for basal metabolic rate in mice affects the abundance of UCP1 protein: implications for translational studies

Low basal metabolic rate (BMR) is a risk factor for obesity, whereas elevation of non-shivering thermogenesis (NST) is a promising means to combat obesity. Because heat generated by NST covers thermogenic needs not fulfilled by BMR, one can expect the presence of a negative relationship between both parameters. Understanding of the mechanisms underlying this relationship is therefore important for interpretation of the results of translational experiments and the development of anti-obesity treatments. We studied two lines of laboratory mice divergently selected for high or low level of BMR, raised at 23°C and subsequently acclimated to different ambient temperatures (30, 23 and 4°C). Mice selected for low BMR accumulated more fat but simultaneously showed higher NST capacity and more uncoupling protein-1 (UCP1) in interscapular brown adipose tissue (iBAT), to compensate for their lower heat production through BMR. The between-line difference in UCP1 protein abundance was significant even in mice acclimated to 30°C when the level of UCP1 is very low. Differences in NST capacity between selected lines and acclimation temperatures were explained by UCP1 iBAT abundance. Our results reveal that BMR is inversely correlated with UCP1 protein abundance and NST, even after acclimation to thermoneutrality. Thus, low values of BMR can increase both obesity risk and the magnitude of NST, i.e. the process whose activation has been proposed to mitigate obesity risk. All these effects should be taken into account in the design and interpretation of translational studies on mice models of metabolic diseases. KEY POINTS: Basal metabolic rate (BMR) and non-shivering thermogenesis (NST) based on the activity of uncoupling protein-1 (UCP1) are two main sources of heat in laboratory mice. Both BMR and UCP1 can affect obesity risk in laboratory rodents and humans. Here we studied BMR, NST, and the abundance of UCP1 in laboratory mice selected divergently towards either high or low BMR. We showed that BMR is negatively correlated with UCP1 abundance and this effect is not removed even after acclimation to thermoneutrality. The pattern described reveals that BMR can affect not only obesity risk but also the magnitude of UCP1-mediated NST. Since activation of NST was proposed to mitigate obesity risk, variation in BMR should be taken into account in translational studies of mouse models of metabolic diseases.

The relationship between resting metabolic rate and quality of life is moderated by age and body composition in women: a cross-sectional study

BACKGROUND

Health-related quality of life (HRQOL) is related to body composition, which is also related to resting metabolic rate (RMR). RMR can be increased by exercise and diet interventions that are not dependent on changes in body composition, so a link between RMR and HRQOL may provide interventions that directly improve HRQOL in women.

METHODS

One hundred twenty women (median age 63.5 [IQR: 53.0-71.0] years) completed one-time measurement of body composition (multi-frequency bioelectrical impedance), RMR (handheld calorimetry), and HRQOL (RAND-36). Physical (PCS) and mental (MCS) composite scores were calculated for the RAND-36. Pearson correlations were used to identify relationships between RMR, body composition, and HRQOL. Variables at the p < .01 level were entered into multiple regression models.

RESULTS

Median body mass index was 26.1 [IQR: 23.2-30.9] kg/m2 and median lean mass index was 16.1 [IQR: 14.6-17.3] kg/m2. Body composition consisted of fat mass (median 27.2 [IQR: 20.3-34.7] kg) and lean mass (median 42.7 [IQR: 38.2-46.9] kg). Median RMR was 1165.0 [IQR: 1022.5-1380.0] kcal/day. Median HRQOL scores were PCS (84.0 [IQR: 74.0-93.0]) and MCS (85.0 [IQR: 74.3-90.0]). RMR was not directly related to PCS, but was directly and negatively related to MCS (p = .002). RMR was significantly and positively related to body composition (lean mass: p < .001; fat mass: p < .001), body mass index (p = .005), and lean mass index (p < .001); but only fat mass (PCS: p < .001; MCS: p < .001) and body mass index (PCS: p < .001; MCS: p < .001) were related to HRQOL, although the relationship was negative. In addition, age was found to be significantly negatively related to RMR (p < .001) and PCS (p = .003). Regression models confirmed the moderating influence of age and body composition on the relationship between RMR and HRQOL. RMR, age, fat mass, and body mass index explained 24% (p < .001) of variance in PCS; and RMR, fat mass, and body mass index explained 15% (p < .001) of variance in MCS.

CONCLUSION

In women, the relationship between RMR and HRQOL is moderated by age and body composition. Understanding these pathways will allow clinicians and researchers to direct interventions more effectively.

A genetic variant of fatty acid amide hydrolase (FAAH) exacerbates hormone-mediated orexigenic feeding in mice

Fatty acid amide hydrolase (FAAH) degrades the endocannabinoid anandamide. A polymorphism in FAAH (FAAH C385A) reduces FAAH expression, increases anandamide levels, and increases the risk of obesity. Nevertheless, some studies have found no association between FAAH C385A and obesity. We investigated whether the environmental context governs the impact of FAAH C385A on metabolic outcomes. Using a C385A knock-in mouse model, we found that FAAH A/A mice are more susceptible to glucocorticoid-induced hyperphagia, weight gain, and activation of hypothalamic AMP-activated protein kinase (AMPK). AMPK inhibition occluded the amplified hyperphagic response to glucocorticoids in FAAH A/A mice. FAAH knockdown exclusively in agouti-related protein (AgRP) neurons mimicked the exaggerated feeding response of FAAH A/A mice to glucocorticoids. FAAH A/A mice likewise presented exaggerated orexigenic responses to ghrelin, while FAAH knockdown in AgRP neurons blunted leptin anorectic responses. Together, the FAAH A/A genotype amplifies orexigenic responses and decreases anorexigenic responses, providing a putative mechanism explaining the diverging human findings.

Motus Vita Est: Fruit Flies Need to Be More Active and Sleep Less to Adapt to Either a Longer or Harder Life

Background: Activity plays a very important role in keeping bodies strong and healthy, slowing senescence, and decreasing morbidity and mortality. Drosophila models of evolution under various selective pressures can be used to examine whether increased activity and decreased sleep duration are associated with the adaptation of this nonhuman species to longer or harder lives. Methods: For several years, descendants of wild flies were reared in a laboratory without and with selection pressure. To maintain the “salt” and “starch” strains, flies from the wild population (called “control”) were reared on two adverse food substrates. The “long-lived” strain was maintained through artificial selection for late reproduction. The 24 h patterns of locomotor activity and sleep in flies from the selected and unselected strains (902 flies in total) were studied in constant darkness for at least, 5 days. Results: Compared to the control flies, flies from the selected strains demonstrated enhanced locomotor activity and reduced sleep duration. The most profound increase in locomotor activity was observed in flies from the starch (short-lived) strain. Additionally, the selection changed the 24 h patterns of locomotor activity and sleep. For instance, the morning and evening peaks of locomotor activity were advanced and delayed, respectively, in flies from the long-lived strain. Conclusion: Flies become more active and sleep less in response to various selection pressures. These beneficial changes in trait values might be relevant to trade-offs among fitness-related traits, such as body weight, fecundity, and longevity.

Resting metabolic rate, abdominal fat pad and liver metabolic gene expression in female rats provided a snacking diet from weaning to adulthood

Our female rat model with continuous, ad libitum access to snacks and chow from weaning to adulthood closely mimics human feeding behavior from childhood onwards. It causes weight gain, enlarged abdominal fat pads, reduced insulin sensitivity and leptin resistance without an increase in total caloric intake. Our current study investigated if this change in energy partitioning is due to a decrease in resting metabolic rate (RMR). In addition, we determined if carbohydrate and lipid metabolism changes in abdominal fat pads and liver. RMR, using indirect calorimetry, was determined in control and snacking rats every two weeks from Days 28-29 to Days 76-77. RMR decreased with age in both groups, but there was no difference between snacking and control rats at any age. At termination, abdominal fat pads (parametrial, retroperitoneal and mesenteric) and liver samples were collected for determination of gene expression for 21 genes involved in carbohydrate and lipid metabolism using RT-qPCR. Analysis of gene expression data showed a striking difference between metabolic profiles of control and snacking rats in abdominal fat pads and liver, with a distinct segregation of genes for both lipid and carbohydrate metabolism that correlated with an increase in body weight and fat pad weights. Genes involved in lipogenesis were upregulated in abdominal fat pads, while genes involved in adipogenesis, and lipid recycling were upregulated in the liver. In conclusion, snacking in addition to chow from weaning in female rats causes a repartitioning of energy that is not due to depressed RMR in snacking rats. Rather, snacking from weaning causes a shift in gene expression resulting in energy partitioning toward enhanced abdominal fat pad lipogenesis, and adipogenesis and lipid recycling in liver.

Body Composition Differences Between Excess Weight Loss ≥ 50% and < 50% at 12 Months Following Bariatric Surgery

Background

The relationship between weight loss and body composition is undefined after bariatric surgery. The objective of this study was to compare body composition changes in patients with excess weight loss ≥ 50% (EWL ≥ 50) and < 50% at 12 months post-operatively (EWL < 50).

Methods

A prospective cohort study was completed on patients undergoing bariatric surgery at two tertiary hospitals between 2017 and 2021. Body composition was measured with dual-energy X-ray absorptiometry immediately before surgery, and at 1, 6, and 12 months post-operatively. Body mass index (BMI), fat mass (FM), lean body mass (LBM), and skeletal muscle index (SMI) trajectories were analysed between patients with EWL ≥ 50% and EWL < 50%.

Results

Thirty-seven patients were included in this series (EWL ≥ 50% n = 25, EWL < 50% n = 12), comprising of both primary and revisional bariatric surgery cases, undergoing a sleeve gastrectomy (62.2%), Roux-en-Y gastric bypass (32.4%), or one anastomosis gastric bypass (5.4%). The EWL ≥ 50% group demonstrated a more optimal mean FM-to-LBM loss ratio than the EWL < 50% group. EWL ≥ 50% patients lost 2.0 kg more FM than EWL < 50% patients for each 1 kg of LBM lost. EWL ≥ 50% was also associated with an increase in mean SMI% over 12 months (5.5 vs. 2.4%; p < 0.0009). Across the whole cohort, the first month after surgery accounted for 67.4% of the total LBM reduction that occurred during the 12-month post-operative period.

Conclusion

This data suggests EWL ≥ 50% is associated with a more optimal body composition outcome than EWL < 50%. LBM reduction occurs predominantly in the early post-operative period.

Graphical abstract

Supplementary Information

The online version contains supplementary material available at 10.1007/s11695-022-06128-3.

Longitudinal analysis of resting energy expenditure and body mass composition in physically active children and adolescents

Background

Monitoring body composition and changes in energy expenditure during maturation and growth is significant, as many components can influence body structure in adulthood. In the case of young players, when these changes can influence their strength and power, it seems to be equally important. Our aim was to examine whether resting energy expenditure (REE) and body composition would change after 10 months from baseline in physically active children and adolescents.

Methods

We obtained data from 80 children and adolescents aged 9 to 17 years at two measurement points: the baseline in September 2018 and after 10 months in July 2019. The study was carried out using a calorimeter (Fitmate MED, Cosmed, Rome, Italy), a device used to assess body composition using by the electrical bioimpedance method by means of a segment analyzer (TANITA MC-980). The Student’s t-test and linear regression analysis were used. Using the stepwise forward regression procedure, the selection of factors in a statistically significant way that describes the level of REE was made.

Results

We noticed that REE was not significantly different between baseline (1596.94 ± 273.01 kcal) and after 10 months (1625.38 ± 253.26 kcal). When analyzing the difference in REE between studies girls, we found body height as a significant predictor. The results of our study show a negative relationship between growth and REE. Differences between sexes and age in REE between baseline and after 10 months were not significant.

Conclusions

Our study involving physically active children and adolescents, which used repeated objective measures and longitudinal statistical modeling to analyze them, was unable to demonstrate any interaction between body weight change, body composition measurements, and REE.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12887-022-03326-x.

Branched Chain Amino Acid Supplementation to a Hypocaloric Diet Does Not Affect Resting Metabolic Rate but Increases Postprandial Fat Oxidation Response in Overweight and Obese Adults after Weight Loss Intervention

Background: Branched chain amino acids (BCAA) supplementation is reported to aid in lean mass preservation, which may in turn minimize the reduction in resting metabolic rate (RMR) during weight loss. Our study aimed to examine the effect of BCAA supplementation to a hypocaloric diet on RMR and substrate utilization during a weight loss intervention. Methods: A total of 111 Chinese subjects comprising 55 males and 56 females aged 21 to 45 years old with BMI between 25 and 36 kg/m² were randomized into three hypocaloric diet groups: (1) standard-protein (14%) with placebo (CT), (2) standard-protein with BCAA, and (3) high-protein (27%) with placebo. Indirect calorimetry was used to measure RMR, carbohydrate, and fat oxidation before and after 16 weeks of dietary intervention. Results: RMR was reduced from 1600 ± 270 kcal/day to 1500 ± 264 kcal/day (p < 0.0005) after weight loss, but no significant differences in the change of RMR, respiratory quotient, and percentage of fat and carbohydrate oxidation were observed among the three diet groups. Subjects with BCAA supplementation had an increased postprandial fat (p = 0.021) and decreased postprandial carbohydrate (p = 0.044) oxidation responses compared to the CT group after dietary intervention. Conclusions: BCAA-supplemented standard-protein diet did not significantly attenuate reduction of RMR compared to standard-protein and high-protein diets. However, the postprandial fat oxidation response increased after BCAA-supplemented weight loss intervention.

Variants of the cry 1 gene may influence the effect of fat intake on resting metabolic rate in women with overweight of obesity: a cross-sectional study

BACKGROUND

Previous studies have shown that the minor allele (C allele) for Cry 1 rs2287161, may be associated with increased risk of cardiovascular diseases (CVDs). Low resting metabolic rate (RMR) caused by the diet has been shown to have, potentially, unfavorable effects on obesity. This study sought to investigate the interactions between the Cry 1 Gene and fat intake on RMR in women with overweight of obesity.

METHODS

This comparative cross-sectional study was conducted on 377 Iranian women with overweight of obesity. A food frequency questionnaire (FFQ), with 147 items, was used to assess dietary intake. Individuals were categorized into two groups based on the rs2287161 genotype. Body composition, dietary intake, and RMR were assessed for all participants.

RESULTS

There was a significant difference between genotypes for fasting blood sugar (FBS) (P = 0.04), fat free mass (FFM) (P = 0.0009), RMR per FFM (P = 0.05), RMR per body mass index (BMI) (P = 0.02), and RMR deviation (P = 0.01). Our findings also showed significant interactions between total fat and C allele carrier group on RMR per kg body weight, RMR per body surface area (BSA), RMR per FFM, and RMR deviation (P for interaction < 0.1), in addition to a significant interaction between CC + CG group genotype and polyunsaturated fatty acids (PUFA) intake on RMR per BMI (P for interaction =0.00) and RMR per kg (P for interaction = 0.02) and RMR per BSA (P = 0.07), compared to the GG group, after control for confounder factors.

CONCLUSION

These results highlight that dietary compositions, gene variants, and their interaction, should be acutely considered in lower RMR.

Significance of variation in basal metabolic rate in laboratory mice for translational experiments

The basal metabolic rate (BMR) accounts for 60–70% of the daily energy expenditure (DEE) in sedentary humans and at least 50% of the DEE in laboratory mice in the thermoneutral zone. Surprisingly, however, the significance of the variation in the BMR is largely overlooked in translational research using such indices as physical activity level (PAL), i.e., the ratio of DEE/BMR. In particular, it is unclear whether emulation of human PAL in mouse models should be carried out within or below the thermoneutral zone. It is also unclear whether physical activity within the thermoneutral zone is limited by the capacity to dissipate heat generated by exercise and obligatory metabolic processes contributing to BMR. We measured PAL and spontaneous physical activity (SPA) in laboratory mice from two lines, divergently selected towards either high or low level of BMR, and acclimated to 30 °C (i.e., the thermoneutral zone), 23 or 4 °C. The mean PAL did not differ between both lines in the mice acclimated to 30 °C but became significantly higher in the low BMR mouse line at the lower ambient temperatures. Acclimation to 30 °C reduced the mean locomotor activity but did not affect the significant difference observed between the selected lines. We conclude that carrying out experiments within the thermoneutral zone can increase the consistency of translational studies aimed at the emulation of human energetics, without affecting the variation in physical activity correlated with BMR.

Energy Balance and Control of Body Weight: Possible Effects of Meal Timing and Circadian Rhythm Dysregulation

Conservation of the energy equilibrium can be considered a dynamic process and variations of one component (energy intake or energy expenditure) cause biological and/or behavioral compensatory changes in the other part of the system. The interplay between energy demand and caloric intake appears designed to guarantee an adequate food supply in variable life contexts. The circadian rhythm plays a major role in systemic homeostasis by acting as “timekeeper” of the human body, under the control of central and peripheral clocks that regulate many physiological functions such as sleep, hunger and body temperature. Clock-associated biological processes anticipate the daily demands imposed by the environment, being synchronized under ideal physiologic conditions. Factors that interfere with the expected demand, including daily distribution of macronutrients, physical activity and light exposure, may disrupt the physiologic harmony between predicted and actual behavior. Such a desynchronization may favor the development of a wide range of disease-related processes, including obesity and its comorbidities. Evidence has been provided that the main components of 24-h EE may be affected by disruption of the circadian rhythm. The sleep pattern, meal timing and meal composition could mediate these effects. An increased understanding of the crosstalk between disruption of the circadian rhythm and energy balance may shed light on the pathophysiologic mechanisms underlying weight gain, which may eventually lead to design effective strategies to fight the obesity pandemic.

The association between deficiency of nutrient intake and resting metabolic rate in overweight and obese women: a cross-sectional study

OBJECTIVE

The double burden of malnutrition is an emerging public health concern nowadays which a correlation with obesity. This study aimed to examine the relationship between resting metabolic rate (RMR) and dietary intake of zinc, vitamin C, and riboflavin in overweight and obese women.

RESULTS

The RMR/FFM showed a significant association with riboflavin (β = 1.59; 95% CI 1.04-23.26, P = 0.04) and zinc (β = 0.78; 95% CI 1.04-4.61, P = 0.03) in the crude model. Moreover, differences in vitamin C and RMR/FFM was marginal significant (β = 0.75; 95% CI 0.95-4.77, P = 0.06). After adjusting for confounders the riboflavin association change to marginal significance (β = 1.52; 95% CI 0.91-23.04, P = 0.06). After controlling for potential confounders, the associations change between zinc and RMR/FFM (β = 0.66; 95% CI 0.78-4.86, P = 0.15) and between RMR/FFM and vitamin C (β = 0.48; 95% CI 0.66-3.96, P = 0.28). Our study showed a significant association between dietary intake of zinc, riboflavin, and vitamin C and change in RMR/FFM in overweight and obese women.

Design of a randomised controlled trial: does indirect calorimetry energy information influence weight loss in obesity?

INTRODUCTION

Respiratory quotient (RQ) provides an indication of the relative balance of carbohydrate and fat oxidation. RQ could serve as an early biomarker of negative energy balance during weight loss. Restriction of energy intake relative to total daily energy requirements produces a negative energy balance which can lead to a fall in RQ, accompanied by a decrease in resting energy expenditure (REE). However, the net change in body weight does not usually match predicted weight change due to intraindividual metabolic adaptations. Our aim is to determine the effectiveness of utilising EE information from indirect calorimetry during weight loss intervention.

METHODS AND ANALYSIS

We will undertake an assessor-blinded, parallel-group randomised controlled trial of 105 adults with obesity randomised in 1:1 ratio to receive either standard weight management care (SC) or EE information plus SC (INT) during a 24-week multicomponent weight management programme. The primary outcome is difference in weight loss between INT and SC group at 24 weeks. Secondary outcomes include: change in RQ, REE, glycaemic variability, and appetite-relating gut hormones (glucagon-like peptide 1, gastric inhibitory polypeptide, peptide YY). Generalised linear mixed models (intention to treat) will assess outcomes for treatment (INT vs SC), time (baseline, 24 weeks) and the treatment-by-time interaction. This will be the first study to evaluate impact of utilising measured REE and RQ on the lifestyle-based intensive intervention programme.

ETHICS AND DISSEMINATION

Ethics approval was obtained from the Health Research Authority and the North West Research Ethics Committee (18/NW/0645). Results from this trial will be disseminated through publication in peer-reviewed journals, national and international presentations.

TRIAL REGISTRATION NUMBERS

NCT03638895; UoL001379.

RMR-Related MAP2K6 Gene Variation on the Risk of Overweight/Obesity in Children: A 3-Year Panel Study

From a pilot GWAS, seven MAP2K6 (MEK6) SNPs were significantly associated with resting metabolic rate (RMR) in obese children aged 8-9 years. The aim of this study was to investigate how RMR-linked MEK6 variation affected obesity in Korean children. With the follow-up students (77.9%) in the 3-year panel study, the changes of the variables associated with obesity (such as anthropometrics, blood biochemistry, and dietary intake) were collected. After the MEK6 SNPs were screened by Affymetrix Genome-Wide Human SNP array 6.0, the genotyping of the seven MEK6 SNPs was performed via SNaPshot assay. As the prevalence of obesity (≥85th percentile) increased from 19.4% to 25.5%, the rates of change of the variables RMR, body mass index (BMI), waist circumference (WC), systolic blood pressure (SBP), and dietary intake (energy and carbohydrate intakes) increased. The rate of overweight/obesity was higher in all mutant alleles of the seven MEK6 SNPs than it was in the matched children without mutant alleles. However, over the 3-year study period, RMRs were only significantly increased by the mutants of two single nucleotide polymorphisms (SNPs), rs996229 and rs756942, mainly related to male overweight/obesity as both WC and SBP levels increased. In the mutants of two of the SNPs, the odds ratio of overweight/obesity risk was six times higher in the highest tercile of fat intake and SBP than those of the lowest tercile. For personalized medicine to prevent pediatric obesity, SBP, WC, and dietary fat intake should be observed, particularly if boys have mutants of MEK6 SNPs, rs9916229, or rs756942.

Early changes in appetite and energy expenditure are not associated to body weight and fat losses in pre-menopausal women living with overweight/obesity

BACKGROUND

The aim of the study was to investigate whether early changes (1-week) in energy balance-related measures would predict changes in body weight (BW) and fat losses in women living with overweight/obesity.

METHODS

BW, body composition (DXA), resting energy expenditure (REE)(indirect calorimetry), olfactory performance (Sniffin' Sticks), appetite and palatability (visual analogue scale) were measured at baseline, after a 1-week of caloric restriction as well as post-intervention (at 10 and 20 weeks) in a group of 30 women living with overweight/obesity.

RESULTS

A significant decrease in REE (p = 0.033) was noted after 1 week. Fasting desire to eat (p = 0.004), hunger (p = 0.001) and prospective food consumption (p = 0.001) all increased after 1 week. Similarly, significant increases in AUC SQ for desire to eat (p = 0.01), hunger (p = 0.005) and prospective food consumption (p = 0.001) were noted after 1 week. However, these early changes were not associated to final BW or FM losses at the end of the weight loss intervention.

CONCLUSION

Despite significant changes in REE and appetite soon after the onset of a BW loss intervention, these early changes do not seem to predict final BW or FM losses at the end of the program in women living with overweight/obesity.

Lack of a relationship between vitamin D status and resting metabolic rate in Iranian adults

OBJECTIVES

Studies suggest a positive relationship between 25-hydroxy vitamin D (25(OH)D)) and resting metabolic rate (RMR). We aimed to determine whether this relationship was also true of populations with very low vitamin D status.

METHODS

Fat mass (FM) and fat free mass (FFM) were determined from multifrequency bioimpedance analysis (InBody 720, Korea). RMR was based on indirect calorimetry (Cortex Metalyser 3B, Germany). Fasting blood measurements of 25(OH)D concentration, glucose and triglycerides were measured. Data were analyzed separately on men and women by tertile of vitamin D status and multiple linear regression analysis.

RESULTS

Two hundred and sixty-three subjects (115 males; 148 females) with a mean age of 37 years and mean %body fat of 30.5% were studied. In women but not men, age, body weight, waist circumference, FM, and FFM increased significantly across tertiles of 25(OH)D. However, there was no difference in unadjusted or adjusted RMR across tertiles of 25OHD in both women and men. Stepwise forward regression analysis showed that age and FFM in men, age and FM in women but not by 25(OH)D, were determinants of RMR. In addition, RMR adjusted for age, sex, FM, FFM and triglyceride-glucose index did not relate to 25(OH)D when linear (r = 0, P = .98), quadratic (r = 0.008, P = .34), or cubic (r = 0.010, P = .43) relationships were tested.

CONCLUSIONS

Residual variation in RMR did not relate to vitamin D status in a group of Iranian adults with very low vitamin D status. Future studies could examine whether such a relationship holds true, after the normalization of vitamin D status.

Associations of nicotidamide-N-methyltransferase, FTO, and IRX3 genetic variants with body mass index and resting energy expenditure in Mexican subjects

The enzyme nicotidamide-N-methyltransferase (NNMT) regulates adipose tissue energy expenditure through increasing nicotinamide adenosine dinucleotide (NAD⁺) content. NNMT methylates nicotinamide to N¹-methylnicotidamide (MNA-1) using S-adenosyl methionine. The rs694539 NNMT polymorphism is associated with non-alcoholic steatohepatitis, and rs1941404 is associated with hyperlipidemia. The rs1421085 FTO is related to poor eating behaviors, and rs3751723 IRX3 is associated with obesity. To investigate the association of rs694539 and rs1941404 NNMT, rs140285 FTO and rs3751723 IRX3 polymorphisms with MNA-1 concentrations, resting energy expenditure (REE) and BMI, we included clinically healthy Mexican subjects 30 to 50 years old, 100 subjects (35 men/65 women) with BMI > 30 kg/m² and 100 subjects (32 men/68 women) with BMI < 25 kg/m². Glucose, lipid profile, insulin, leptin, acylated ghrelin, and MNA-1 (LC–MS) were quantified. Resting energy expenditure (REE) was estimated using indirect calorimetry with a Fitmate instrument. Genotyping was performed using PCR–RFLP, and allelic discrimination was examined using TaqMan probes. MNA-1 concentrations and REE were significantly higher in obese subjects. Subjects with the rs694539AA NNMT genotype (recessive model) had lower weight, BMI, and REE. BMI showed an association with HDL-C, triglycerides, MNA-1, acetylated ghrelin, leptin, insulin concentrations, HOMA-IR, REE, and rs1421085. Subjects with the TC or CC genotypes of rs1421085 FTO showed 6 kg and 2 units of BMI more than did those with the TT wild type. The CG of the rs1421085 and rs3751723 haplotypes was associated with BMI. These findings showed that BMI was strongly associated with REE, rs1421085 FTO and the CG rs1421085 FTO and rs3751723 IRX3 haplotypes. We used the GMDR approach in obesity phenotype to show the interaction of four SNPs and metabolic variables.

Low basal metabolic rate as a risk factor for development of insulin resistance and type 2 diabetes

INTRODUCTION

Identification of physiological factors influencing susceptibility to insulin resistance and type 2 diabetes (T2D) remains an important challenge for biology and medicine. Numerous studies reported energy expenditures as one of those components directly linked to T2D, with noticeable increase of basal metabolic rate (BMR) associated with the progression of insulin resistance. Conversely, the putative link between genetic, rather than phenotypic, determination of BMR and predisposition to development of T2D remains little studied. In particular, low BMR may constitute a considerable risk factor predisposing to development of T2D.

RESEARCH DESIGN AND METHODS

We analyzed the development of insulin resistance and T2D in 20-week-old male laboratory mice originating from three independent genetic line types. Two of those lines were subjected to divergent, non-replicated selection towards high or low body mass-corrected BMR. The third line type was non-selected and consisted of randomly bred animals serving as an outgroup (reference) to the selected line types. To induce insulin resistance, mice were fed for 8 weeks with a high fat diet; the T2D was induced by injection with a single dose of streptozotocin and further promotion with high fat diet. As markers for insulin resistance and T2D advancement, we followed the changes in body mass, fasting blood glucose, insulin level, lipid profile and mTOR expression.

RESULTS

We found BMR-associated differentiation in standard diabetic indexes between studied metabolic lines. In particular, mice with low BMR were characterized by faster body mass gain, blood glucose gain and deterioration in lipid profile. In contrast, high BMR mice were characterized by markedly higher expression of the mTOR, which may be associated with much slower development of T2D.

CONCLUSIONS

Our study suggests that genetically determined low BMR makeup involves metabolism-specific pathways increasing the risk of development of insulin resistance and T2D.

Metabolic Factors Determining the Susceptibility to Weight Gain: Current Evidence

PURPOSE OF REVIEW

There is substantial inter-individual variability in body weight change, which is not fully accounted by differences in daily energy intake and physical activity levels. The metabolic responses to short-term perturbations in energy intake can explain part of this variability by quantifying the degree of metabolic "thriftiness" that confers more susceptibility to weight gain and more resistance to weight loss. It is unclear which metabolic factors and pathways determine this human "thrifty" phenotype. This review will investigate and summarize emerging research in the field of energy metabolism and highlight important metabolic mechanisms implicated in body weight regulation in humans.

RECENT FINDINGS

Dysfunctional adipose tissue lipolysis, reduced brown adipose tissue activity, blunted fibroblast growth factor 21 secretion in response to low-protein hypercaloric diets, and impaired sympathetic nervous system activity might constitute important metabolic factors characterizing "thriftiness" and favoring weight gain in humans. The individual propensity to weight gain in the current obesogenic environment could be ascertained by measuring specific metabolic factors which might open up new pathways to prevent and treat human obesity.

Global, regional and time-trend prevalence of central obesity: a systematic review and meta-analysis of 13.2 million subjects

We aimed to examine the global prevalences of central obesity according to age, sex, race, place of residence, geographical region, national income level, and the definitions of central obesity. MEDLINE and Embase were searched. Studies with sample size of ≥ 500 and investigated individuals aged ≥ 15 years were included. Metaprop (a Stata command) was adopted to conduct a meta-analysis of prevalence, and the Freeman-Tukey Double Arcsine Transformation was used to stabilize the variances. A random-effects model was used to evaluate the prevalence and 95% confidence intervals (CI) of central obesity. There were 288 studies involving 13,233,675 individuals in this analysis. The overall prevalence of central obesity was 41.5% (95% CI 39.9–43.2%). A higher prevalence was found in older individuals, female subjects, urban residents, Caucasians, and populations of higher income level countries. Regarding regional variations, the highest prevalence was found in Sothern America (55.1%, 95% CI 45.8–64.3%) and Central American (52.9%, 95% CI 32.7–72.7%). Its prevalence was rapidly rising from 1985 to 2014. From 1985–1999 to 2010–2014, younger subjects aged 15–40 years showed a more drastic rise in prevalence (16.3 to 33.9%) than subjects aged > 40 years (43.6 to 57.9%). Male individuals have a more drastic rise (25.3 to 41.6%) than females (38.6 to 49.7%). Major increasing in prevalence of the condition in the past three decades, particularly in certain subgroups. These findings could act as a useful reference to inform public health strategies to minimize the impact of central obesity on population health.

Baseline Metabolic Variables Do Not Predict Weight Regain in Premenopausal Women

OBJECTIVE

The aim of this study was to investigate whether baseline (pre-weight loss) metabolic variables can predict weight regain.

METHODS

About 117 women with overweight completed a weight loss program to achieve BMI < 25 kg/m2 and were followed for 2 years. Resting metabolic rate, respiratory quotient, insulin sensitivity, and serum leptin concentration were measured pre-weight loss, while on energy balance, and as predictors of weight regain at 1 and 2 years. Rate and amount of weight loss also were examined as predictors, as these outcomes may reflect metabolic phenotype.

RESULTS

Average weight loss was 12 (SD 2.5) kg, and regain was 48% (SD 35%) and 80% (SD 52%) at 1 and 2 years, respectively. In regression modeling, metabolic variables (both pre-weight loss and changes with weight loss) did not predict weight regain. However, initial weight loss and time to achieve BMI < 25 were significant predictors of weight regain at 1 and 2 years, even after adjusting for confounders.

CONCLUSIONS

Baseline (pre-weight loss) resting metabolic rate, respiratory quotient, insulin sensitivity, and leptin did not predict weight regain. However, a larger and faster weight loss was associated with a lower weight regain. Understanding the mechanisms behind interindividual variation in magnitude and rate of weight loss is needed to ensure better weight loss maintenance.

Basal metabolic rate and Charlson Comorbidity Index are independent predictors of metabolic syndrome in patients with rheumatoid arthritis

OBJECTIVE

To prospectively analyze predictors of metabolic syndrome (MetS) in patients with rheumatoid arthritis (RA) during 2years of follow-up.

METHODS

We recruited 319 consecutive patients with RA who did not have MetS. MetS was defined in accordance with the modified National Cholesterol Education Program/Adult Treatment Panel III 2005 for Asian populations. Sociodemographic data, laboratory findings, disease activity data, and medication history were collected during face-to-face interviews at baseline and follow-up. Independent predictors of MetS were assessed by univariate and multivariate logistic regression analyses.

RESULTS

Of the 247 patients with RA who completed the 2-year follow-up, 37 (15.0%) developed MetS. At baseline, these patients were older and had higher body mass index, waist circumference, waist-hip ratio, skeletal muscle mass, body fat mass, percent body fat, and Charlson Comorbidity Index scores, as well as lower basal metabolic rate (BMR). Moreover, these patients with MetS took less hydroxychloroquine and more oral hypoglycemic agents; they also had lower European Quality of Life Health-state Questionnaire scores. After exclusion of variables associated with MetS composition, multivariate analysis identified BMR (odds ratio [OR]=0.205, 95% confidence interval [CI]: 0.078-0.541, P=0.001) and Charlson Comorbidity Index score (OR=2.191, 95% CI: 1.280-3.751, P=0.004) as significant predictors of MetS.

CONCLUSIONS

Our study showed that the annual incidence rate of MetS was 11.5% in patients with RA. Moreover, the development of MetS was associated with BMR and Charlson Comorbidity Index score at baseline.

Resting Energy Expenditure and Substrate Oxidation in Malnourished Patients With Type 1 Glycogenosis

CONTEXT

Type 1a and 1b glycogenosis [glycogen storage disorder (GSD)1a, GSD1b] are rare diseases generally associated with malnutrition. Although abnormal substrate oxidation rates and elevated energy expenditures might contribute to malnutrition, this issue has not been investigated.

OBJECTIVE

To investigate whether abnormal resting energy expenditure (REE) and substrate oxidation rate characterize patients with GSD1.

DESIGN

Cross-sectional study.

SETTING

Outpatient referral center for rare diseases and laboratory of clinical nutrition at the University Hospital of Palermo.

PATIENTS

Five consecutive patients with GSD1 (4 type a, 1 type b; 3 men, 2 women; age range, 19 to 49 years).

MAIN OUTCOME MEASURES

The usual clinical procedures for patients with malnutrition, including REE and basal substrate oxidation rate (both indirect calorimetry), body composition (bioimpedance method), muscle strength (hand-grip test), and the usual laboratory tests, were performed.

RESULTS

Malnutrition was clearly diagnosed in 2 patients (1 GSD1a and 1 GSD1b), with REE elevated in all five patients, and especially, in the two malnourished patients (+124% and +32.1% vs predictive values using Harris-Benedict equations). The two malnourished patients also exhibited lower basal protein oxidation rates (7.7% and 6.6%) than the nourished patients (range, 12.1% to 24.7%), with higher carbohydrate or lipid oxidation rates. Additionally, the two malnourished patients exhibited higher blood concentrations of lactic acid than the nourished patients.

CONCLUSIONS

According to data obtained from our small sample of patients with GSD1, elevated REEs seem to be a common characteristic that might contribute to malnutrition. Low basal protein oxidation rates and elevated blood lactic acid concentrations appear to be associated with malnutrition.

Low capacity to oxidize fat and body weight

For a given positive energy balance, a low capacity to oxidize fat could contribute to weight gain (low fat oxidation hypothesis). This hypothesis is based on the arguments that for a given stable diet and food quotient (FQ), the respiratory quotient (RQ) is higher in obesity prone (OP) than in obesity resistant individuals (OR) and that a high RQ predicts higher future weight gain. A review of 42 studies shows that there is no convincing experimental support to these arguments and thus for the low fat oxidation hypothesis. A power analysis also shows that this hypothesis might be impossible to experimentally confirm because very large numbers of subjects would be needed to reject the null hypotheses that the 24-h RQ is not different in OP and OR or that future weight gain is not different in individuals with a low and high 24-h RQ at baseline. A re-examination of the significance of the 24-hour and fasting RQ also shows that the assumption underlying the low fat oxidation hypothesis that a high RQ reflects a low capacity to oxidize fat is not valid: For a stable diet, the 24-h RQ entirely depends on FQ and energy balance, and the fasting RQ mainly depends on the FQ and energy balance and on the size of glycogen stores.

Impact of Hepatic Steatosis on Resting Metabolic Rate and Metabolic Adaptation in Response to Intentional Weight Loss

Weight loss is the primary intervention for nonalcoholic fatty liver disease (NAFLD). A decrease in resting metabolic rate (RMR) out of proportion to the degree of weight loss may promote weight regain. We aimed to determine the impact of hepatic steatosis on weight loss‐associated changes in RMR and metabolic adaptation, defined as the difference between predicted and measured RMR after weight loss. We retrospectively analyzed prospectively collected data from 114 subjects without diabetes (52 with NAFLD), with body mass index (BMI) >35, and who enrolled in a 6‐month weight loss intervention. Hepatic steatosis was determined by unenhanced computed tomography scans by liver:spleen attenuation ratio <1.1. RMR was measured by indirect calorimetry. At baseline, patients with hepatic steatosis had higher BMI, fat mass (FM), fat‐free mass (FFM), and RMR (RMR, 1,933 kcal/day; 95% confidence interval [CI], 841‐2,025 kcal/day; versus 1,696; 95% CI, 1,641‐1,751; P < 0.0001). After 6 months, the NAFLD group experienced larger absolute declines in weight, FM, and FFM, but percentage changes in weight, FFM, and FM were similar between groups. A greater decline in RMR was observed in patients with NAFLD (−179 kcal/day; 95% CI, −233 to −126 kcal/day; versus −100; 95% CI, −51 to −150; P = 0.0154) for the time × group interaction, and patients with NAFLD experienced greater metabolic adaptation to weight loss (−97 kcal/day; 95% CI, −143 to −50 kcal/day; versus −31.7; 95% CI, −74 to 11; P = 0.0218) for the prediction × group interaction. The change (Δ) in RMR was significantly associated with ΔFM, ΔFFM, and baseline RMR, while metabolic adaptation was significantly associated with female sex and ΔFM only. Conclusion: Hepatic steatosis is associated with a greater reduction in FM, which predicts RMR decline and a higher metabolic adaptation after weight loss, potentially increasing the risk of long‐term weight regain.

Metabolic Determinants of Weight Gain in Humans

One of the fundamental challenges in obesity research is to identify subjects prone to weight gain so that obesity and its comorbidities can be promptly prevented or treated. The principles of thermodynamics as applied to human body energetics demonstrate that susceptibility to weight gain varies among individuals as a result of interindividual differences in energy expenditure and energy intake, two factors that counterbalance one another and determine daily energy balance and, ultimately, body weight change. This review focuses on the variability among individuals in human metabolism that determines weight change. Conflicting results have been reported about the role of interindividual differences in energy metabolism during energy balance in relation to future weight change. However, recent studies have shown that metabolic responses to acute, short-term dietary interventions that create energy imbalance, such as low-protein overfeeding or fasting for 24 hours, may reveal the underlying metabolic phenotype that determines the degree of resistance to diet-induced weight loss or the propensity to spontaneous weight gain over time. Metabolically "thrifty" individuals, characterized by a predilection for saving energy in settings of undernutrition and dietary protein restriction, display a minimal increase in plasma fibroblast growth factor 21 concentrations in response to a low-protein overfeeding diet and tend to gain more weight over time compared with metabolically "spendthrift" individuals. Similarly, interindividual variability in the causal relationship between energy expenditure and energy intake ("energy sensing") and in the metabolic response to cold exposure (e.g., brown adipose tissue activation) seems, to some extent, to be indicative of individual propensity to weight gain. Thus, an increased understanding and the clinical characterization of phenotypic differences in energy metabolism among individuals (metabolic profile) may lead to new strategies to prevent weight gain or improve weight-loss interventions by targeted therapies on the basis of metabolic phenotype and susceptibility to obesity in individual persons.

Integration of transcriptomic data in a genome-scale metabolic model to investigate the link between obesity and breast cancer

BACKGROUND

Obesity is a complex disorder associated with an increased risk of developing several comorbid chronic diseases, including postmenopausal breast cancer. Although many studies have investigated this issue, the link between body weight and either risk or poor outcome of breast cancer is still to characterize. Systems biology approaches, based on the integration of multiscale models and data from a wide variety of sources, are particularly suitable for investigating the underlying molecular mechanisms of complex diseases. In this scenario, GEnome-scale metabolic Models (GEMs) are a valuable tool, since they represent the metabolic structure of cells and provide a functional scaffold for simulating and quantifying metabolic fluxes in living organisms through constraint-based mathematical methods. The integration of omics data into the structural information described by GEMs allows to build more accurate descriptions of metabolic states.

RESULTS

In this work, we exploited gene expression data of postmenopausal breast cancer obese and lean patients to simulate a curated GEM of the human adipocyte, available in the Human Metabolic Atlas database. To this aim, we used a published algorithm which exploits a data-driven approach to overcome the limitation of defining a single objective function to simulate the model. The flux solutions were used to build condition-specific graphs to visualise and investigate the reaction networks and their properties. In particular, we performed a network topology differential analysis to search for pattern differences and identify the principal reactions associated with significant changes across the two conditions under study.

CONCLUSIONS

Metabolic network models represent an important source to study the metabolic phenotype of an organism in different conditions. Here we demonstrate the importance of exploiting Next Generation Sequencing data to perform condition-specific GEM analyses. In particular, we show that the qualitative and quantitative assessment of metabolic fluxes modulated by gene expression data provides a valuable method for investigating the mechanisms associated with the phenotype under study, and can foster our interpretation of biological phenomena.

A low resting metabolic rate in late childhood is associated with weight gain in adolescence

BACKGROUND AND OBJECTIVES

Lower total energy expenditure (TEE) and resting metabolic rate (RMR) are associated with greater weight gain in Native American adults. Whether these effects exist in childhood is unclear. We hypothesized that lower energy expenditure measured in childhood would predict greater relative change in body mass index (BMI) during adolescence.

METHODS

Measurements of height, weight, body composition, RMR and TEE were completed in 181 Native American children at exams done at age 5 and 10years, with 126 children having biennial follow-up assessments of weight and height after age 10years until age 20years. TEE and RMR were adjusted for age, sex, height, fat mass and fat free mass. BMI-change was assessed using population specific and Center for Disease Control (CDC) BMI z-scores and change in the relative difference to the 95th BMI-centile.

RESULTS

Lower adjusted RMR at age 10years was associated with greater increase in population-specific and CDC BMI z-scores, greater increase in the relative difference to the 95th BMI-centile and greater weight gain (all r≤-0.22, p≤0.01). However, no association was found with adjusted RMR at age 5years and with adjusted TEE and physical activity level assessed at age 5 or 10years.

CONCLUSIONS

Lower adjusted RMR at age 10years predicted greater change in adolescent BMI z-score indicating that the effects of relatively low metabolic rate on future weight gain in this population may begin in late childhood.

Cognitive dietary restraint, disinhibition, and hunger are associated with 24-h energy expenditure

Background:

Higher energy expenditure (EE) is associated with greater food intake, possibly because the human body senses EE and modifies eating behaviors to regulate food intake and ultimately achieve energy balance. As eating behaviors are also influenced by social and cultural factors, any association between EE and eating behavior may differ between ethnicities and sexes.

Objective:

To assess relationships between EE and eating behavior constructs of the Three-Factor Eating Questionnaire (TFEQ).

Subjects/Methods:

307 healthy adults (201M/106F, 160 Native Americans) completed the TFEQ and had measures of 24-h EE in a whole-room calorimeter during energy balance. Body composition was assessed by DXA.

Results:

On average, adjusted 24-h EE was lower (β=−229 kcal/day, CI: −309-−148, p<0.001) but cognitive restraint (Δ=+1.5; CI: 0.5–2.5, p=0.003) and disinhibition (Δ=+2.1, CI: 1.3–2.8, p<0.001) scores were higher in women compared to men. In Native Americans, adjusted 24-h EE (β=+94 kcal/day, CI: 48–139, p<0.001) and disinhibition scores (Δ=+1.0, CI: 0.1–2.0, p=0.003) were higher compared to other ethnicities. Higher 24-h EE associated with lower cognitive restraint in women (ρ=−0.20, p=0.04), but not men (p=0.71; interaction term p=0.01) with no ethnic differences. Greater 24-h EE associated with higher disinhibition (ρ=0.20, p=0.001) and hunger cues (ρ=0.16, p=0.004) with no gender differences. These associations were primarily present in non-Native Americans (ρ=0.23, p=0.006 and ρ=0.25, p=0.003) but not observed in Native Americans (both p>0.40).

Conclusions:

Higher EE is associated with psychological constructs of eating behaviors that favors overeating including lower cognitive restraint, higher dietary disinhibition, and greater susceptibility to hungers cues, supporting the existence of energy-sensing mechanisms influencing human eating behavior. These associations were observed in ethnicities other than Native Americans, possibly explaining the contradictory relationships reported between EE and weight change in different ethnic groups. We propose that increased EE may alter eating behaviors, potentially leading to uncontrolled overeating and weight gain.

Beneficial Effects of Vitamin D on Insulin Sensitivity, Blood Pressure, Abdominal Subcutaneous Fat Thickness, and Weight Loss in Refractory Obesity

IN BRIEF This study explored the impact of correcting vitamin D deficiency on blood pressure, metabolic status, and weight loss in patients with fatigue and obesity refractory to conventional interventions such as diet, exercise, behavioral modification, and pharmacotherapy. Correction of vitamin D deficiency in such patients was found to be significantly associated with weight reduction and improved insulin sensitivity.

Successful and unsuccessful weight-loss maintainers: strategies to counteract metabolic compensation following weight loss

Adaptive thermogenesis and reduced fat oxidative capacity may accompany weight loss, continuing in weight maintenance. The present study aimed (1) to determine whether weight-reduced and weight-loss relapsed women are at greater metabolic risk for weight gain compared with BMI-matched controls with no weight-loss history, and (2) to identify protective strategies that might attenuate weight loss-associated adaptive thermogenesis and support successful weight-loss maintenance. Four groups of women were recruited: reduced-overweight/obese (RED, n 15), controls (low-weight stable weight; LSW, n 19) BMI <27 kg/m²; relapsed-overweight/obese (REL, n 11), controls (overweight/obese stable weight; OSW, n 11) BMI >27 kg/m². Body composition (bioelectrical impedance), 75 g oral glucose tolerance test, fasting and postprandial metabolic rate (MR) and substrate utilisation (RER) and physical activity (accelerometer (7 d)) were measured. Sociobehavioural questionnaires and 3 × 24 h diet recalls were completed. Fasting and postprandial MR, RER and total daily energy intake (TDEI) were not different between RED and REL v. controls (P > 0·05). RED consumed less carbohydrate (44·8 (sd 10·3) v. 53·4 (sd 10·0) % TDEI, P = 0·020), more protein (19·2 (sd 6·0) v. 15·6 (sd 4·2) % TDEI, P = 0·049) and increased physical activity, but behaviourally reported greater dietary restraint (P = 0·002) compared with controls. TDEI, macronutrient intake and physical activity were similar between OSW and REL. REL reported higher subjective fasting and lower postprandial ratings of prospective food consumption compared with OSW. Weight-reduced women had similar RMR (adjusted for fat-free mass) compared with controls with no weight-loss history. Increased physical activity, higher protein intake and greater lean muscle mass may have counteracted weight loss-associated metabolic compensation and highlights their importance in weight-maintenance programmes.

A bedtime milk snack does not impact RMR, substrate utilisation and appetite the following morning in mildly overweight males

Nighttime eating is often associated with a negative impact on weight management and cardiometabolic health. However, data from recent acute metabolic studies have implicated a benefit of ingesting a bedtime snack for weight management. The present study compared the impact of ingesting a milk snack containing either 10 (BS10) or 30 g (BS30) protein with a non-energetic placebo (BS0) 30 min before bedtime on next morning metabolism, appetite and energy intake in mildly overweight males (age: 24·3 (sem 0·8) years; BMI: 27·4 (sem 1·1) kg/m2). Next morning measurements of RMR, appetite and energy intake were measured using indirect calorimetry, visual analogue scales and an ad libitum breakfast, respectively. Bedtime milk ingestion did not alter next morning RMR (BS0: 7822 (sem 276) kJ/d, BS10: 7482 (sem 262) kJ/d, BS30: 7851 (sem 261) kJ/d, P=0·19) or substrate utilisation as measured by RER (P=0·64). Bedtime milk ingestion reduced hunger (P=0·01) and increased fullness (P=0·04) during the evening immediately after snack ingestion, but elicited no effect the next morning. Next morning breakfast (BS0: 2187 (sem 365) kJ, BS10: 2070 (sem 336) kJ, BS30: 2582 (sem 384) kJ, P=0·21) and 24 h post-trial (P=0·95) energy intake was similar between conditions. To conclude, in mildly overweight adults, compared with a non-energetic placebo, a bedtime milk snack containing 10 or 30 g of protein does not confer changes in next morning whole-body metabolism and appetite that may favour weight management.

Energy expenditure and substrate oxidation in White and African American young adults without obesity

It has been hypothesized that the increased risk of obesity among African Americans may be partially explained by low energy expenditure (EE) and impaired fat oxidation. Twelve White adults without obesity were pair-matched by age, sex and body mass index (BMI) to a sample of 12 African Americans. Resting EE (REE), 24-h EE, 24-h RQ, Sleep EE, Sleep RQ and spontaneous physical activity were measured in a respiratory chamber; and free-living total daily EE (TDEE) and physical activity EE were measured using doubly labeled water. There were no race differences in age, body composition, 24-h RQ, sleep RQ, or spontaneous or free-living physical activity; however, Whites had significantly higher REE (p=0.02), 24-h EE (p=0.02), Sleep EE (p=0.005); but not TDEE (p=0.30) compared to African Americans after adjustment for FFM. African Americans may have a higher risk for obesity because of lower energy expenditure.

Energy expenditure in the etiology of human obesity: spendthrift and thrifty metabolic phenotypes and energy-sensing mechanisms

The pathogenesis of human obesity is the result of dysregulation of the reciprocal relationship between food intake and energy expenditure (EE), which influences daily energy balance and ultimately leads to weight gain. According to principles of energy homeostasis, a relatively lower EE in a setting of energy balance may lead to weight gain; however, results from different study groups are contradictory and indicate a complex interaction between EE and food intake which may differentially influence weight change in humans. Recently, studies evaluating the adaptive response of one component to perturbations of the other component of energy balance have revealed both the existence of differing metabolic phenotypes ("spendthrift" and "thrifty") resulting from overeating or underfeeding, as well as energy-sensing mechanisms linking EE to food intake, which might explain the propensity of an individual to weight gain. The purpose of this review is to debate the role that human EE plays on body weight regulation and to discuss the physiologic mechanisms linking EE and food intake. An increased understanding of the complex interplay between human metabolism and food consumption may provide insight into pathophysiologic mechanisms underlying weight gain, which may eventually lead to prevention and better treatment of human obesity.

Metabolic risk factors in mice divergently selected for BMR fed high fat and high carb diets

Factors affecting contribution of spontaneous physical activity (SPA; activity associated with everyday tasks) to energy balance of humans are not well understood, as it is not clear whether low activity is related to dietary habits, precedes obesity or is a result of thereof. In particular, human studies on SPA and basal metabolic rates (BMR, accounting for >50% of human energy budget) and their associations with diet composition, metabolic thrift and obesity are equivocal. To clarify these ambiguities we used a unique animal model-mice selected for divergent BMR rates (the H-BMR and L-BMR line type) presenting a 50% between-line type difference in the primary selected trait. Males of each line type were divided into three groups and fed either a high fat, high carb or a control diet. They then spent 4 months in individual cages under conditions emulating human "sedentary lifestyle", with SPA followed every month and measurements of metabolic risk indicators (body fat mass %, blood lipid profile, fasting blood glucose levels and oxidative damage in the livers, kidneys and hearts) taken at the end of study. Mice with genetically determined high BMR assimilated more energy and had higher SPA irrespective of type of diet. H-BMR individuals were characterized by lower dry body fat mass %, better lipid profile and lower fasting blood glucose levels, but higher oxidative damage in the livers and hearts. Genetically determined high BMR may be a protective factor against diet-induced obesity and most of the metabolic syndrome indicators. Elevated spontaneous activity is correlated with high BMR, and constitutes an important factor affecting individual capability to sustain energy balance even under energy dense diets.

Does basal metabolic rate predict weight gain?

BACKGROUND

Some previous studies have indicated that a low basal metabolic rate (BMR) is an independent predictor of future weight gain, but low rates of follow-up and highly select populations may limit the ability to generalize the results.

OBJECTIVE

We assessed whether adults with a low BMR gain more weight than do adults with a high BMR who are living in a typical Western environment.

DESIGN

We extracted BMR, body-composition, demographic, and laboratory data from electronic databases of 757 volunteers who were participating in our research protocols at the Mayo Clinic between 1995 and 2012. Research study volunteers were always weight stable, had no acute illnesses and no confounding medication use, and were nonsmokers. The top and bottom 15th percentiles of BMR, adjusted for fat-free mass (FFM), fat mass, age, and sex, were identified. Follow-up electronic medical record system data were available for 163 subjects, which allowed us to determine their subsequent weight changes for ≥3 y (mean: ∼9.7 y).

RESULTS

By definition, the BMR was different in the high-BMR group (2001 ± 317 kcal/d; n = 86) than in the low-BMR group (1510 ± 222 kcal/d; n = 77), but they were comparable with respect to age, body mass index, FFM, and fat mass. Rates of weight gain were not greater in the bottom BMR group (0.3 ± 1.0 kg/y) than in the top BMR group (0.5 ± 1.5 kg/y) (P = 0.17).

CONCLUSION

Adults with low BMRs did not gain more weight than did adults with high BMRs, implying that habitual differences in food intake or activity counterbalance variations in BMR as a risk factor for weight gain in a typical Western population.

Reduced Resting Metabolic Rate in Adults with Hemiparetic Chronic Stroke

OBJECTIVE

Resting metabolic rate (RMR) is the component of energy expenditure that explains the largest proportion of total daily energy requirements. Since RMR is determined largely by fat-free mass and a low RMR predicts weight gain in healthy adults, identifying the role of muscle atrophy following stroke on RMR may help identify ways to mitigate the development of obesity post-stroke.

METHODS

Thirty-nine stroke survivors with chronic hemiparesis (mean ± SEM: age: 61 ± 1 years, latency from stroke: 107 ± 40 months, BMI: 31 ± 3 kg/m2) underwent DXA scans for measurement of body composition, including total, paretic, and non-paretic leg lean mass and fasted, 30-min indirect calorimetry for measurement of RMR.

RESULT

Predicted RMR was calculated by the Mifflin-St Jeor equation, which considers weight, height, and age for both men and women. RMR was 14% lower than predicted (1438 ± 45 vs. 1669 ± 38 kcals/24 hrs; P<0.01). Total (r=0.73, P<0.01), paretic (r=0.72, P<0.01) and non-paretic (r=0.67, P<0.01) leg lean mass predicted RMR.

CONCLUSION

These data indicate that muscle atrophy post stroke may lead to a reduced RMR. This substantiates the need to attenuate the loss of lean mass after a stroke to prevent declines in RMR and possible weight gain common post-stroke.

Possible resting metabolic rate modification by the circulating RBP4 in obese subjects

AIM

Adipose tissue derived retinol-binding protein 4 (RBP-4), known as one of the most important adipokins, has a link with insulin resistance and metabolic syndrome in obesity. The purpose of this study was to investigate the possible correlation between fasting serum RBP4 and resting metabolic rate (RMR) as a predictor of weight gain, body composition and insulin resistance in obese and non-obese subjects.

MATERIALS AND METHODS

In this case-control study, 73 obese and 90 non-obese participants were assessed following an overnight fasting for RMR by means of indirect calorimetry. Body composition was measured using body composition analyzer. Serum RBP4 levels were quantified by ELISA method.

RESULTS

Circulating RBP4 level correlated positively with log insulin (r=0.278, p=0.04) in obese subjects. There were no significant correlation between RBP4 and body composition in obese subjects except fat free mass (r=0.42, p=0.001). We found reduced RMR/kg in higher RBP4 concentration, moreover, a negative correlation was found between RBP4 and RMR/kg (r=-0.35, p=0.01) in obese group. Based on ROC analysis and RMR/kg cut-off value (=20 kcal/24 h/kg) for predicting the risk of obesity, 83.3% of participants with RMR/kg<20 kcal/24 h/kg had high RBP4 concentration, however in subjects with RMR/kg≥20 kcal/24 h/kg this percentage was 16.7 (p=0.01).

CONCLUSION

Our findings demonstrated that RBP4 concentration had relation with RMR which was different among obese and non-obese groups. These results may suggest the possible role of RBP4 in alteration of metabolic rate through insulin or other metabolic effects.

Resting energy expenditure in type 2 diabetic patients and the effect of insulin bolus

AIMS

Resting energy expenditure (REE) plays a critical role in the regulation of body weight, with important implications in type 2 diabetes (T2D). However, the relationships between REE and T2D have not been extensively evaluated. We compared REE in persons with diabetes and in persons without diabetes. We also investigated the acute effect of insulin on REE and venous lactate, the latter an indirect measure of neoglucogenetic activity.

METHODS

REE was measured using indirect calorimetry in 14 newly diagnosed, untreated T2D adults and in 14 non-diabetic age-, gender- and body mass index-matched persons. The REE and lactate venous concentrations were also measured in a subgroup of 5 T2D patients in the hour following an IV insulin bolus.

RESULTS

The REE normalized for fat-free mass (FFM) was significantly higher in T2D patients than in the group without diabetes (mean ± SD: 27.6 ± 1.9 vs. 25.8 ± 1.9 kcal/kg-FFM·24h; P=0.02). REE normalized for FFM was correlated with fasting plasma glucose concentration (r=0.51; P=0.005). Following the insulin venous bolus REE (0': 2,048 ± 242; 10': 1,804 ± 228; 20': 1,684 ± 230; 30': 1,634 ± 212; 45': 1,594 ± 179; 60': 1,625 ± 197 kcal/24h; P<0.001) and both glucose (P<0.001) and lactate (P<0.001) concentrations progressively declined in the ensuing hour.

CONCLUSIONS

Patients with diabetes have a higher energy expenditure, likely a consequence of higher gluconeogenetic activity. This study may contribute to recognizing the nature of body weight reduction that occurs in concomitance with poorly controlled diabetes, and of body weight gain as commonly observed when hypoglycemic treatment is started.

Lower "awake and fed thermogenesis" predicts future weight gain in subjects with abdominal adiposity

Awake and fed thermogenesis (AFT) is the energy expenditure (EE) of the nonactive fed condition above the minimum metabolic requirement during sleep and is composed of the thermic effect of food and the cost of being awake. AFT was estimated from whole-room 24-h EE measures in 509 healthy subjects (368 Native Americans and 141 whites) while subjects consumed a eucaloric diet. Follow-up data were available for 290 Native Americans (median follow-up time: 6.6 years). AFT accounted for ~10% of 24-h EE and explained a significant portion of deviations from expected energy requirements. Energy intake was the major determinant of AFT. AFT, normalized as a percentage of intake, was inversely related to age and fasting glucose concentration and showed a nonlinear relationship with waist circumference and BMI. Spline analysis demonstrated that AFT becomes inversely related to BMI at an inflection point of 29 kg/m(2). The residual variance of AFT, after accounting for covariates, predicted future weight change only in subjects with a BMI >29 kg/m(2). AFT may influence daily energy balance, is reduced in obese individuals, and predicts future weight gain in these subjects. Once central adiposity develops, a blunting of AFT may occur that then contributes to further weight gain.

Predictors of body composition and body energy changes in response to chronic overfeeding

Objective

We have previously shown that 24 young lean men (12 pairs of identical twins) subjected to a standardized 353 MJ (84 000 kcal) overfeeding protocol over 100 days exhibited individual differences in body weight and composition gains. The mean (+SD) gains in fat mass (FM) and fat-free mass (FFM) were 5.4+1.9 kg and 2.7+1.5 kg for a total body energy (BE) gain of 221+75 MJ representing 63% of the energy surplus consumed. We report here on the most important baseline correlates of these overfeeding-induced changes with the aim of identifying biomarkers of the response.

Results

Baseline maximal oxygen uptake per kilogram body mass was negatively correlated with gains in weight, FM, and BE (all p<0.05). Enzyme activities indicative of skeletal muscle oxidative potential correlated with gains in FM and BE (all p<0.05). Baseline TSH levels in response to a TRH stimulation correlated positively with changes in FM-to-FFM ratio (p<0.05). Plasma concentrations of androstenediol-sulfate, dehydroepiandrosterone, and 17-hydroxy pregnenolone were negatively correlated with gains in FM and BE (0.01<p<0.05), while level of estrone was negatively and androsterone-glucoronide was positively correlated with FFM gains (p<0.05). Baseline leptin and abdominal fat cell size correlated positively with gains in weight, FM, and BE (p<0.05). When compared to the six highest BE gainers, the six lowest gainers exhibited higher thermic effect of a meal (TEM) and plasma levels of total testosterone, cortisol, estradiol, androstenedione, and androstenediol-sulfate (all p<0.05). High baseline levels of total TEM, testosterone, and androstenediol-sulfate were associated with lower FM gains whereas high baseline levels of FT4 and estrone were found in low-FFM gainers.

Conclusion

Although none of the variables exerted individually an overwhelmingly strong influence on overfeeding-induced changes, baseline FFM, maximal oxygen uptake, muscle oxidative capacity, androgens, and leptin levels were the most consistent significant biomarkers of the responsiveness to chronic overfeeding.

Lower energy expenditure predicts long-term increases in weight and fat mass

CONTEXT

The relevance of the contribution of energy expenditure (EE) and substrate oxidation to weight change has not been fully confirmed.

OBJECTIVE

The objective of the study was to determine whether metabolic parameters measured in a whole room indirect calorimeter are predictive of long-term body weight change.

SETTING

The study was conducted at a clinical research unit in Phoenix, Arizona, from 1985 to 2005.

PARTICIPANTS

A total of 612 healthy subjects (384 males and 228 females; aged 29.5 ± 8.1 years; body mass index 33.0 ± 8.7 kg/m(2); percent body fat 30.9 ± 9.6%), including 422 Native Americans and 190 whites. Follow-up data were available for 292 Native Americans with a median follow-up time of 6.7 years (interquartile range 3.9-10.5).

MAIN OUTCOME MEASURES

Twenty-four-hour EE, sleeping metabolic rate, daily (fed) and sleeping (fasting) respiratory quotient, and carbohydrate and fat oxidation rates were measured during a 24-hour respiratory chamber. Body composition was assessed by underwater weighing or dual-energy x-ray absorptiometry.

RESULTS

After accounting for demographic and body composition measures, the remaining variance of 24-hour EE was inversely related to the rate of weight change (ρ = -0.158, P = .007) and fat mass change (ρ = -0.179, P = .012), such that 100 kcal below the expected 24-hour EE corresponded to 0.2 kg/y weight gain, of which 0.1 kg/y was fat mass. Deviations from the predicted values of the sleeping metabolic rate (ρ = -0.121, P = .039) and fed respiratory quotient (ρ = 0.119, P = .042) were also associated with future weight change, whereas the fat oxidation rate was inversely associated with weight change in men (ρ = -0.174, P = .024) but not in women (ρ = 0.018, P = .853).

CONCLUSIONS

Measures of energy expenditure and substrate oxidation are predictors of long-term weight change, indicating a small but significant role for reduced metabolic rate in weight gain.

Resting metabolic rate is associated with hunger, self-determined meal size, and daily energy intake and may represent a marker for appetite

BACKGROUND

There are strong logical reasons why energy expended in metabolism should influence the energy acquired in food-intake behavior. However, the relation has never been established, and it is not known why certain people experience hunger in the presence of large amounts of body energy.

OBJECTIVE

We investigated the effect of the resting metabolic rate (RMR) on objective measures of whole-day food intake and hunger.

DESIGN

We carried out a 12-wk intervention that involved 41 overweight and obese men and women [mean ± SD age: 43.1 ± 7.5 y; BMI (in kg/m(2)): 30.7 ± 3.9] who were tested under conditions of physical activity (sedentary or active) and dietary energy density (17 or 10 kJ/g). RMR, daily energy intake, meal size, and hunger were assessed within the same day and across each condition.

RESULTS

We obtained evidence that RMR is correlated with meal size and daily energy intake in overweight and obese individuals. Participants with high RMRs showed increased levels of hunger across the day (P < 0.0001) and greater food intake (P < 0.00001) than did individuals with lower RMRs. These effects were independent of sex and food energy density. The change in RMR was also related to energy intake (P < 0.0001).

CONCLUSIONS

We propose that RMR (largely determined by fat-free mass) may be a marker of energy intake and could represent a physiologic signal for hunger. These results may have implications for additional research possibilities in appetite, energy homeostasis, and obesity. This trial was registered under international standard identification for controlled trials as ISRCTN47291569.

High energy expenditure masks low physical activity in obesity

OBJECTIVE

To investigate energy expenditure in lean and obese individuals, focusing particularly on physical activity and severely obese individuals.

DESIGN

Total daily energy expenditure (TDEE) was assessed using doubly labeled water, resting metabolic rate (RMR) by indirect calorimetry, activity energy expenditure (AEE) by difference and time spent in physical activity by multisensor activity monitors.

SUBJECTS

In all, 177 lean, Class I and severely obese individuals (age 31-56 years, body mass index 20-64 kg m(-2)) were analyzed.

RESULTS

All components of energy expenditure were elevated in obese individuals. For example, TDEE was 2404±95 kcal per day in lean and 3244±48 kcal per day in Class III obese individuals. After appropriate adjustment, RMR was similar in all groups. Analysis of AEE by body weight and obesity class indicated a lower AEE in obese individuals. Confirming lower physical activity, obese individuals spent less time engaged in moderate-to-vigorous physical activity (2.7±1.3, 1.8±0.6, 2.0±1.4 and 1.2±1.0 h per day in lean, Class I, Class II and Class III individuals) and more time in sedentary behaviors.

CONCLUSIONS

There was no indication of metabolic efficiency in even the severely obese, as adjusted RMR was similar across all groups. The higher AEE observed in the obese is consistent with a higher cost of activities due to higher body weight. However, the magnitude of the higher AEE (20-25% higher in obese individuals) is lower than expected (weight approximately 100% higher in Class III individuals). Confirming a lower volume of physical activity in the obese, the total time spent in moderate-to-vigorous physical activity and average daily metabolic equivalent of task level were lower with increasing obesity. These findings demonstrate that high body weight in obese individuals leads to a high TDEE and AEE, which masks the fact that they are less physically active, which can be influenced by duration or intensity of activity, than in lean individuals.