Reduction of sleeping metabolic rate after vertical banded gastroplasty

Weight Loss Strategies

Lifestyle interventions for weight loss combine support for changing diet and physical activity with weight management education and are considered the first line treatment for obesity. A variety of diet-focused interventions including time-restricted eating are also increasingly being promoted for weight management. This chapter reviews different types of interventions for weight management, their underlying health behavior change models, and effectiveness to date in randomized trials. The results justify increasing efforts to improve program effectiveness generally, and to personalize interventions to support long-term adherence. The high prevalence of obesity worldwide, combined with the known increase in risk of non-communicable diseases with duration of excess weight, provides a compelling justification for routine delivery of effective weight management interventions in the community and in clinical care.

Effect of very large body mass loss on energetics, mechanics and efficiency of walking in adults with obesity: mass-driven versus behavioural adaptations

Abstract

Understanding the mechanisms involved in the higher energy cost of walking (NC_w: the energy expenditure above resting per unit distance) in adults with obesity is pivotal to optimizing the use of walking in weight management programmes. Therefore, this study aimed to investigate the mechanics, energetics and mechanical efficiency of walking after a large body mass loss induced by bariatric surgery in individuals with obesity. Nine adults (39.5 ± 8.6 year; BMI: 42.7 ± 4.6 kg m^–2) walked at five fixed speeds before (baseline) and after the bariatric surgery (post 1 and post 2). Gas exchanges were measured to obtain NC_w. A motion analysis system and instrumented treadmill were combined to assess total mechanical work (W_tot). Mechanical efficiency (W_tot NC_w^–1) was also calculated. Participants lost 25.7 ± 3.4% of their body mass at post 1 (6.6 months; P < 0.001) and 6.1 ± 4.9% more at post 2 (12 months; P = 0.014). Mass‐normalized NC_w was similar between baseline and post 1 and decreased at post 2 compared to that at baseline (−6.2 ± 2.7%) and post 1 (−8.1 ± 1.9%; P ≤ 0.007). No difference was found in mass‐normalized W_tot during follow‐up (P = 0.36). Mechanical efficiency was similar at post 1 and post 2 when compared to that at baseline (P ≥ 0.19), but it was higher (+14.1 ± 4.6%) at post 2 than at post 1 (P = 0.013). These findings showed that after a very large body mass loss, individuals with obesity may reorganize their walking pattern into a gait more similar to that of lean adults, thus decreasing their NC_w by making their muscles work more efficiently.

Key points

A higher net (above resting) energy cost of walking (lower gait economy) is observed in adults with obesity compared to lean individuals.

Understanding the mechanisms (i.e. mass driven, gait pattern and behavioural changes) involved in this extra cost of walking in adults with obesity is pivotal to optimizing the use of walking to promote daily physical activity and improve health in these individuals.

We found that very large weight loss induced by bariatric surgery significantly decreased the energy cost of walking per kg of body mass after 1 year with similar total mechanical work per kg of body mass, resulting in an increased mechanical efficiency of walking.

Individuals with obesity may reorganize their walking pattern into a gait more similar to that of adults of normal body mass, thus decreasing their energy cost of walking by making their muscles work more efficiently.

Resting Energy Expenditure and Organ-Tissue Body Composition 5 Years After Bariatric Surgery

INTRODUCTION

Bariatric surgery-induced weight loss may reduce resting energy expenditure (REE) and fat-free mass (FFM) disproportionately thereby predisposing patients to weight regain and sarcopenia.

METHODS

We compared REE and body composition of African-American and Caucasian Roux-en-Y gastric bypass (RYGB) patients after surgery with a group of non-operated controls (CON). REE by indirect calorimetry; skeletal muscle (SM), trunk organs, and brain volumes by MRI; and FFM by DXA were measured at post-surgery visits and compared with CON (N = 84) using linear regression models that adjusted for relevant covariates. Ns in RYGB were 50, 42, and 30 for anthropometry and 39, 27, 17 for MRI body composition at years 1, 2, and 5 after surgery, respectively.

RESULTS

Regression models adjusted for age, weight, height, ethnicity, and sex showed REE differences (RYGB minus CON; mean ± s.e.): year 1 (43.2 ± 34 kcal/day, p = 0.20); year 2 (- 27.9 ± 37.3 kcal/day, p = 0.46); year 5 (114.6 ± 42.3 kcal/day, p = 0.008). Analysis of FFM components showed that RYGB had greater trunk organ mass (~ 0.4 kg) and less SM (~ 1.34 kg) than CON at each visit. REE models adjusted for FFM, SM, trunk organs, and brain mass showed no between-group differences in REE (- 15.9 ± 54.8 kcal/day, p = 0.8; - 46.9 ± 64.9 kcal/day, p = 0.47; 47.7 ± 83.0 kcal/day, p = 0.57, at years 1, 2, and 5, respectively).

CONCLUSIONS

Post bariatric surgery patients maintain a larger mass of high-metabolic rate trunk organs than non-operated controls of similar anthropometrics. Interpreting REE changes after weight loss requires an accurate understanding of fat-free mass composition at both the organ and tissue levels.

CLINICAL TRIAL REGISTRATION

Long-term Effects of Bariatric Surgery (LABS-2) NCT00465829.

Changes in Resting Energy Expenditure in Relation to Body Weight and Composition Following Gastric Restriction: A Systematic Review

In comparison to gastric bypass surgery, gastric restriction without malabsorption more closely simulates dietary adherence while still producing durable weight loss. The latter is achieved despite considerable reductions in resting energy expenditure (REE), and whether REE is adjusted for body weight/composition using ratio- or regression-based methods could influence understanding of how these procedures affect energy balance. This systematic review identified studies that reported REE before and after gastric restriction in order to compare changes using each method. Ratio assessments revealed increases and decreases when REE was expressed per kilogram of body weight and per kilogram of fat-free mass, respectively. In comparison, measured REE tended to be less than predicted from linear regression after surgery. Explanations for these seemingly disparate findings and future directions are discussed.

Nutritional and Micronutrient Care of Bariatric Surgery Patients: Current Evidence Update

PURPOSE OF REVIEW

The continued success of bariatric surgery to treat obesity and obesity-associated metabolic conditions creates a need for a strong understanding of clinical nutrition both before and after these procedures.

RECENT FINDINGS

Surgically induced alteration of gastrointestinal physiology can affect the nutrition of individuals, especially among those who have undergone malabsorptive procedures. While uncommon, a subset of patients may develop protein-calorie malnutrition. In these cases, nutrition support should be tailored to the severity of malnutrition. Among all patients who undergo bariatric surgery, high rates of micronutrient deficiencies have been observed. To mitigate these deficiencies, empiric supplementation with multivitamins, calcium citrate, and vitamin D is generally recommended. Periodic surveillance should be performed for commonly deficient micronutrients, including thiamin (B1), folate (B9), cobalamin (B12), iron, and vitamin D. Following Roux-en-Y gastric bypass, serum levels of copper and zinc should also be monitored. In addition, lipid-soluble vitamins should be monitored following biliopancreatic diversion with/without duodenal switch.

Targeting the gut to treat obesity and its metabolic comorbidities: focus on bariatric surgery - view from the chair

Over the past decade, bariatric surgery emerged as the most effective treatment modality for obesity and its complications, especially type 2 diabetes. Initially introduced on the basis of their capacity to restrict food intake and/or induce dietary fat malabsorption, the current bariatric surgery procedures result in many more physiological changes that may also partly explain their potent and sustained anti-obesity and anti-diabetic effects. In the session 2 of the 17th International Symposium of the Université Laval Research Chair in Obesity, outstanding speakers have provided insight into novel clinical and pathophysiological aspects in bariatric surgery. Dr Blandine Laferrère discussed the growing body of evidence implicating incretin hormones in the anti-diabetic effects of bariatric surgery and Dr Hans-Rudolf Berthoud explored emerging evidence suggesting that bariatric surgery may reset the defended body mass set point. As data are rapidly accruing about the beneficial effects of bariatric surgery, these procedures not only take a greater place in clinical practice, but they also offer outstanding occasions to peek into the intricate and complex links between diet and gastrointestinal track, and obesity and its complications.

Control of energy expenditure in humans

Energy expenditure is determined by body size and body composition and by food intake and physical activity. Body size and body composition are the determinants of resting energy expenditure. Higher weight results in higher energy requirement through a higher resting requirement because of a higher maintenance cost of a larger body. Activity-induced energy expenditure is the most variable component of total energy expenditure. Smaller and leaner subjects generally move more as activity energy expenditure in larger subjects is not higher in proportion to the cost of moving with a higher body weight. Food intake induces changes in energy expenditure as a function of changes in body size and body composition. In addition, energy restriction induces an adaptive reduction of energy expenditure through a lowering of tissue metabolism and a reduction of body movement. An exercise-induced increase in activity expenditure is a function of the training status. In untrained subjects, exercise induces a larger increase in total energy expenditure than can be attributed to the energy cost of a training program. Trained subjects have a higher performance at the same expenditure through a higher exercise economy.

Nutrition care for patients with weight regain after bariatric surgery

Achieving optimal weight outcomes for patients with obesity is important to the management of their chronic disease. All interventions present risks for weight regain. Bariatric surgery is the most efficacious treatment, producing greater weight losses that are sustained over more time compared to lifestyle interventions. However, approximately 20-30% of patients do not achieve successful weight outcomes, and patients may experience a regain of 20-25% of their lost weight. This paper reviews several factors that influence weight regain after bariatric surgery, including type of surgery, food tolerance, energy requirements, drivers to eat, errors in estimating intake, adherence, food and beverage choices, and patient knowledge. A comprehensive multidisciplinary approach can provide the best care for patients with weight regain. Nutrition care by a registered dietitian is recommended for all bariatric surgery patients. Nutrition diagnoses and interventions are discussed. Regular monitoring of weight status and early intervention may help prevent significant weight regain.

Weight loss-induced reduction in physical activity recovers during weight maintenance

BACKGROUND

Weight loss due to a negative energy balance is considered to be accompanied by a decrease in physical activity.

OBJECTIVE

The aim of this study was to investigate whether a decrease in physical activity is sustained during weight maintenance.

DESIGN

Subjects were 20 men and 31 women [mean (±SD) age: 42 ± 8 y; BMI (in kg/m(2)): 31.4 ± 2.8]. Weight loss was achieved by an 8-wk very-low-energy diet period, followed by 44 wk of weight maintenance. Physical activity measures were total energy expenditure expressed as a multiple of sleeping metabolic rate (PALSMR) and resting metabolic rate (PALRMR), activity-induced energy expenditure divided by body weight (AEE/kg), and activity counts measured by a triaxial accelerometer. Measurements took place at 0, 8, and 52 wk.

RESULTS

Body mass decreased significantly during the diet period (10.5 ± 3.8%, P < 0.001), and this reduction was sustained after 52 wk (6.0 ± 5.1%, P < 0.001). PALSMR and PALRMR decreased from 1.81 ± 0.23 and 1.70 ± 0.22, respectively, before the diet to 1.69 ± 0.20 and 1.55 ± 0.19 after the diet (P < 0.001) and increased again after weight maintenance to 1.85 ± 0.27 and 1.71 ± 0.23, respectively, compared with 8-wk measurements (P < 0.001). AEE/kg decreased from 0.043 ± 0.015 MJ/kg at baseline to 0.037 ± 0.014 MJ/kg after the diet (P < 0.001) and was higher after 52 wk (0.044 ± 0.17 MJ/kg) compared with after 8 wk (P < 0.001). Activity counts decreased from 1.64 ± 0.37 megacounts/d at baseline to 1.54 ± 0.35 megacounts/d after the diet (P < 0.05) and were higher after 52 wk (1.73 ± 0.49 megacounts/d) compared with 8 wk (P < 0.01).

CONCLUSION

A weight loss-induced reduction in physical activity returns to baseline values when weight loss is maintained. This trial was registered at clinicaltrials.gov as NCT01015508.

Surgical weight loss: impact on energy expenditure

Diet-induced weight loss is often limited in its magnitude and often of short duration, followed by weight regain. On the contrary, bariatric surgery now commonly used in the treatment of severe obesity favors large and sustained weight loss, with resolution or improvement of most obesity-associated comorbidities. The mechanisms of sustained weight loss are not well understood. Whether changes in the various components of energy expenditure favor weight maintenance after bariatric surgery is unclear. While the impact of diet-induced weight loss on energy expenditure has been widely studied and reviewed, the impact of bariatric surgery on total energy expenditure, resting energy expenditure, and diet-induced thermogenesis remains unclear. Here, we review data on energy expenditure after bariatric surgery from animal and human studies. Bariatric surgery results in decreased total energy expenditure, mainly due to reduced resting energy expenditure and explained by a decreased in both fat-free mass and fat mass. Limited data suggest increased diet-induced thermogenesis after gastric bypass, a surgery that results in gut anatomical changes and modified the digestion processes. Physical activity and sustained intakes of dietary protein may be the best strategies available to increase non-resting and then total energy expenditure, as well as to prevent the decline in lean mass and resting energy expenditure.

Weight loss, weight maintenance, and adaptive thermogenesis

BACKGROUND

Diet-induced weight loss is accompanied by adaptive thermogenesis, ie, a disproportional or greater than expected reduction of resting metabolic rate (RMR).

OBJECTIVE

The aim of this study was to investigate whether adaptive thermogenesis is sustained during weight maintenance after weight loss.

DESIGN

Subjects were 22 men and 69 women [mean ± SD age: 40 ± 9 y; body mass index (BMI; in kg/m(2)): 31.9 ± 3.0]. They followed a very-low-energy diet for 8 wk, followed by a 44-wk period of weight maintenance. Body composition was assessed with a 3-compartment model based on body weight, total body water (deuterium dilution), and body volume. RMR was measured (RMRm) with a ventilated hood. In addition, RMR was predicted (RMRp) on the basis of the measured body composition: RMRp (MJ/d) = 0.024 × fat mass (kg) + 0.102 × fat-free mass (kg) + 0.85. Measurements took place before the diet and 8, 20, and 52 wk after the start of the diet.

RESULTS

The ratio of RMRm to RMRp decreased from 1.004 ± 0.077 before the diet to 0.963 ± 0.073 after the diet (P < 0.001), and the decrease was sustained after 20 wk (0.983 ± 0.063; P < 0.01) and 52 wk (0.984 ± 0.068; P < 0.01). RMRm/RMRp was correlated with the weight loss after 8 wk (P < 0.01), 20 wk (P < 0.05), and 52 wk (P < 0.05).

CONCLUSION

Weight loss results in adaptive thermogenesis, and there is no indication for a change in adaptive thermogenesis up to 1 y, when weight loss is maintained. This trial was registered at clinicaltrials.gov as NCT01015508.

Increased postprandial energy expenditure may explain superior long term weight loss after Roux-en-Y gastric bypass compared to vertical banded gastroplasty

Background and Aims

Gastric bypass results in greater weight loss than Vertical banded gastroplasty (VBG), but the underlying mechanisms remain unclear. In addition to effects on energy intake the two bariatric techniques may differentially influence energy expenditure (EE). Gastric bypass in rats increases postprandial EE enough to result in elevated EE over 24 hours. This study aimed to investigate alterations in postprandial EE after gastric bypass and VBG in humans.

Methods

Fourteen women from a randomized clinical trial between gastric bypass (n = 7) and VBG (n = 7) were included. Nine years postoperatively and at weight stability patients were assessed for body composition and calorie intake. EE was measured using indirect calorimetry in a respiratory chamber over 24 hours and focused on the periods surrounding meals and sleep. Blood samples were analysed for postprandial gut hormone responses.

Results

Groups did not differ regarding body composition or food intake either preoperatively or at study visit. Gastric bypass patients had higher EE postprandially (p = 0.018) and over 24 hours (p = 0.048) compared to VBG patients. Postprandial peptide YY (PYY) and glucagon like peptide 1 (GLP-1) levels were higher after gastric bypass (both p<0.001).

Conclusions

Gastric bypass patients have greater meal induced EE and total 24 hours EE compared to VBG patients when assessed 9 years postoperatively. Postprandial satiety gut hormone responses were exaggerated after gastric bypass compared to VBG. Long-term weight loss maintenance may require significant changes in several physiological mechanisms which will be important to understand if non-surgical approaches are to mimic the effects of bariatric surgery.

Metabolic adaptations to over--and underfeeding--still a matter of debate?

Weight changes in response to a change in energy intake are smaller than calculated from the excess or deficit of energy intake. Digestion efficiency is not affected by intake level when consuming the same diet. Over- or underfeeding induces an increase or decrease in energy expenditure. Intake-induced expenditure changes are largely explained by proportional changes in diet-induced energy expenditure, in activity-induced energy expenditure and in maintenance expenditure as a function of changes in body weight and body composition. Additionally, underfeeding causes a metabolic adaptation as reflected in a reduction of maintenance expenditure below predicted values and defined as adaptive thermogenesis. Thus, alternating overfeeding and underfeeding with an iso-energetic amount results in a positive energy balance. The latter might be one of the explanations for the increasing incidence of obesity in our current society with an ample food supply.

Provision of nutritional support to those experiencing complications following bariatric surgery

This review details the practicalities of providing nutrition support to obese patients who experience complications following bariatric surgery and highlights some of the nutritional challenges encountered by this group of patients. Bariatric surgery to treat morbid obesity has significantly increased internationally over the past decade with hospital admissions rising annually. The gastric bypass is currently the most commonly performed procedure. The complication rate can be up to 16%, with a considerable proportion having nutritional implications. The treatment can involve avoidance of oral diet and nutrition support, i.e. enteral or parenteral nutrition. Opposition to nutrition support can be encountered. It is useful to clarify the aims of nutrition support, these being: the avoidance of overfeeding and its consequences, preservation of lean body mass and promotion of healing. Evidence suggests that hypoenergic nutrition is not harmful and may actually be beneficial. There is a lack of consensus regarding the optimum method to predict the nutritional requirements in the obese acutely unwell patient. The literature suggests that the predicted equations are fairly accurate compared to measured energy expenditure in free living obese patients before and after bariatric surgery. However, these findings cannot be directly applied to those obese patients experiencing complications of bariatric surgery, who will be acutely unwell exhibiting inflammatory response. It is therefore necessary to refer to the literature on energy expenditure in hospitalized obese patients, to help guide practice. More research examining the energy and protein requirements of obese patients needing nutrition support following bariatric surgery is urgently required.

Contribution of individual organ mass loss to weight loss-associated decline in resting energy expenditure

BACKGROUND

Weight loss leads to reduced resting energy expenditure (REE) independent of fat-free mass (FFM) and fat mass (FM) loss, but the effect of changes in FFM composition is unclear.

OBJECTIVE

We hypothesized that a decrease in REE adjusted for FFM with weight loss would be partly explained by a disproportionate loss in the high metabolic activity component of FFM.

DESIGN

Forty-five overweight and obese women [body mass index (in kg/m(2)): 28.7-46.8] aged 22-46 y followed a low-calorie diet for 12.7 +/- 2.2 wk. Body composition was measured by magnetic resonance imaging, dual-energy X-ray absorptiometry, and a 4-compartment model. REE measured by indirect calorimetry (REEm) was compared with REE calculated from detailed body-composition analysis (REEc) by using specific organ metabolic rates (ie, organ REE/mass).

RESULTS

Weight loss was 9.5 +/- 3.4 kg (8.0 +/- 2.9 kg FM and 1.5 +/- 3.1 kg FFM). Decreases in REE (-8%), free triiodothyronine concentrations (-8%), muscle (-3%), heart (-5%), liver (-4%), and kidney mass (-6%) were observed (all P < 0.05). Relative loss in organ mass was significantly higher (P < 0.01) than was the change in low metabolically active FFM components (muscle, bone, and residual mass). After weight loss, REEm - REEc decreased from 0.24 +/- 0.58 to 0.01 +/- 0.44 MJ/d (P = 0.01) and correlated with the decrease in free triiodothyronine concentrations (r = 0.33, P < 0.05). Women with high adaptive thermogenesis (defined as REEm - REEc < -0.17 MJ/d) had less weight loss and conserved FFM, liver, and kidney mass.

CONCLUSIONS

After weight loss, almost 50% of the decrease in REEm was explained by losses in FFM and FM. The variability in REEm explained by body composition increased to 60% by also considering the weight of individual organs.

Dietary fat oxidation as a function of body fat

PURPOSE OF REVIEW

Is trafficking of dietary fat involved in the development of obesity?

RECENT FINDINGS

Studies on energy expenditure and substrate utilization during overfeeding, studies on individual differences in substrate utilization between individuals fed at energy balance, and differences in responses in energy expenditure and substrate utilization in individuals after weight reduction, illustrate that the capacity of fat oxidation is a potential determinant for the development of obesity.

SUMMARY

The ability to store dietary fat seems to be involved in the susceptibility to gain weight during a positive energy balance. Obese individuals show less oxidation and more storage of dietary fat as compared with the lean phenotype. Differences in fuel trafficking make individuals prone to overeating in the current obesogenic environment with a high availability of energy-dense fatty foods. It is difficult to get rid of excess body fat as energy requirement for weight maintenance after weight reduction is lower than predicted from the new body composition reached and thus, there is a high risk for weight regain.

Long-term persistence of adaptive thermogenesis in subjects who have maintained a reduced body weight

BACKGROUND

After weight loss, total energy expenditure -- in particular, energy expenditure at low levels of physical activity -- is lower than predicted by actual changes in body weight and composition. An important clinical issue is whether this reduction, which predisposes to weight regain, persists over time.

OBJECTIVE

We aimed to determine whether this disproportionate reduction in energy expenditure persists in persons who have maintained a body-weight reduction of > or =10% for >1 y.

DESIGN

Seven trios of sex- and weight-matched subjects were studied in an in-patient setting while receiving a weight-maintaining liquid formula diet of identical composition. Each trio consisted of a subject at usual weight (Wt(initial)), a subject maintaining a weight reduction of > or =10% after recent (5-8 wk) completion of weight loss (Wt(loss-recent)), and a subject who had maintained a documented reduction in body weight of >10% for >1 y (Wt(loss-sustained)). Twenty-four-hour total energy expenditure (TEE) was assessed by precise titration of fed calories of a liquid formula diet necessary to maintain body weight. Resting energy expenditure (REE) and the thermic effect of feeding (TEF) were measured by indirect calorimetry. Nonresting energy expenditure (NREE) was calculated as NREE = TEE - (REE +TEF).

RESULTS

TEE, NREE, and (to a lesser extent) REE were significantly lower in the Wt(loss-sustained) and Wt(loss-recent) groups than in the Wt(initial) group. Differences from the Wt(initial) group in energy expenditure were qualitatively and quantitatively similar after recent and sustained weight loss.

CONCLUSION

Declines in energy expenditure favoring the regain of lost weight persist well beyond the period of dynamic weight loss.

Mechanisms of weight loss after bariatric surgery

The surgical treatment of clinically severe obesity is becoming more popular. To date, little has been published concerning the mechanisms by which each of the commonly employed bariatric surgical procedures induces weight loss. This article reviews the physiology of weight loss induced by semi-starvation and other proposed mechanisms of surgically induced weight loss.

Body composition and energy expenditure: relationship and changes in obese subjects before and after biliopancreatic diversion

Changes in total and segmental body composition were studied in 101 obese women before and 2, 6, 12, and 24 months after biliopancreatic diversion (BPD) and data 24 months after surgery were matched to 53 control subjects. The patients were studied by anthropometry, indirect calorimetry, and double-emission x-ray absorptiometry (DXA). The combination of calorimetry and body composition analysis allowed estimation of visceral and muscle lean mass. We observed a significant (analysis of variance [ANOVA]: P <.05) progressive reduction of fat and lean body mass (LBM) following BPD, with stabilization of both parameters between 12 and 24 months at levels not different from controls. Fat loss was significant in the arms, legs, and trunk segments. After 24 months, there was no significant difference in segmental fat mass between post-BPD patients and controls. Calorimetric data seem to confirm lean body mass (LBM) reduction. Visceral lean mass (kg) was significantly reduced from 8.1 +/- 2.2 in obese subjects to 6.5 +/- 1.8 in post-BPD patients at 24 months (P <.05); the control value was 7.2 +/- 1.8. Muscular lean mass (kg) was also significantly reduced, from 50.2 +/- 5.8 to 39.8 +/- 5.7 in the same subjects (P <.05), with a control value of 42.5 +/- 5.9. The decrease in muscle and visceral LBM reached control values without significant differences. Viscera/muscle ratio in pre-BPD patients was preserved in post-BPD patients at 24 months, but it was reduced during weight loss. Body composition studies showed a logarithmic relationship between fat and lean mass and a physiological contribution of lean mass to weight loss in the BPD patients. In conclusion, weight loss after BPD was achieved with an appropriate decline of LBM and with all parameters reaching, at stable weight, values similar to weight-matched controls.

Sleeping metabolic rate in relation to body mass index and body composition

OBJECTIVES

To determine whether patterns of sleeping metabolic rate (SMR) are altered in obesity. Specifically to determine the relationship between changes in SMR and body weight, body mass index (BMI, kg/m(2)), and fat-free mass (FFM); and to compare resting metabolic rate (RMR) with SMR during different periods of sleep.

SUBJECTS

Eighteen healthy, pre-menopausal, obese (BMI >30, n=9) and non-obese (BMI <30, n=9), female subjects (six Caucasians and 12 African-Americans), with an average age of 36 y (range 22-45).

MEASUREMENTS

Total energy expenditure (TEE or 24 h EE), metabolic rate (MR), SMR (minimum, average and maximum) and resting metabolic rate (RMR) or resting energy expenditure (REE) measured by human respiratory chamber, and external mechanical work measured by a force platform within the respiratory chamber. Physical activity index (PAL) was derived as TEE/REE. Body composition was determined by dual-energy X-ray absorptiometry (DXA).

RESULTS

SMR decreased continuously during sleep and reached its lowest point just before the subject was awakened in the morning by the research staff. Although averages for RMR and SMR were similar, RMR was lower than SMR at the beginning of the sleeping period and higher than SMR in the morning hours. The rate of decrease in SMR was faster with increasing body weight (-0.829, P<0.0001), BMI (correlation factor -0.896, P<0.0001) and FFM (-0.798, P=0.001). The relationship between the slope of SMR decrease and BMI (y=-5 x 10(-6)x(2)+0.0002x-0.0028) is highly significant, with a P-value of <0.0001 and r(2) value of 0.9622.

CONCLUSIONS

The rate of decline in metabolic rate during sleep is directly related to body weight, BMI and FFM. Average SMR tends to be lower than RMR in obese subjects and higher than RMR in non-obese subjects.

Evidence for the existence of adaptive thermogenesis during weight loss

The present study was performed to further investigate the adaptive component of thermogenesis that appears during prolonged energy restriction. Fifteen obese men and twenty obese women underwent a 15-week weight-loss programme. During this programme, body weight and composition as well as resting energy expenditure (REE) were measured at baseline, after 2 and 8 weeks of energy restriction (-2929 kJ/d) and drug therapy (or placebo), and finally 2-4 weeks after the end of the 15-week drug therapy and energy restriction intervention, when subjects were weight stable. Regression equations were established in a control population of the same age. These equations were then used to predict REE in obese men and women at baseline, after 2 and 8 weeks, as well as after the completion of the programme. In both men and women body weight and fat mass were significantly reduced in all cases) while fat-free mass remained unchanged throughout the programme. At baseline, REE predicted from the regression equation was not significantly different from the measured REE in men, while in women the measured REE was 13 % greater than predicted. After 2 weeks of energy restriction, measured REE had fallen by 469 and 635 kJ/d more than predicted and this difference reached 963 and 614 kJ/d by week 8 of treatment in men and women respectively. Once body-weight stability was recovered at the end of the programme, changes in REE remained below predicted changes in men (-622 kJ/d). However, in women changes in predicted and measured REE were no longer different at this time, even if the women were maintaining a reduced body weight. In summary, the present results confirm the existence of adaptive thermogenesis and give objective measurements of this component during weight loss in obese men and women, while they also emphasize that in women this component seems to be essentially explained by the energy restriction.

Surgery for obesity

As were most types of gastrointestinal surgery, antiobesity surgery was dominated by the development of laparoscopic techniques during the last decade. The feasibility of performing any primary antiobesity operation safely laparoscopically was convincingly demonstrated during the last 2 years. This represents a significant continued improvement in the perioperative safety of "bariatric" surgery. However, antiobesity surgery entails very much more than technique. Unfortunately, little progress has been made in optimizing patient selection, improving follow-up, and devising strategies for reoperative antiobesity surgery. The latest publications in the field are mainly confirmatory, demonstrating durable medically significant weight loss resulting in comorbidity reduction with increased life expectancy. The most interesting contribution of this surgery is provision of "experimental models" using gastrointestinal physiology to study the pathophysiology of obesity and undernutrition by guaranteeing substantial weight loss maintained long-term. It is unfortunate that surgery for obesity is seriously underutilized.

Energy economy hampers body weight loss after gastric bypass

The impact of energy economy on body weight loss was investigated in 20 obese women, submitted to Roux-en-Y gastric bypass. Resting energy expenditure (REE), substrate oxidation rates, plasma glucose, free fatty acid, and insulin and leptin levels were measured before and 3, 6, and 12 months after surgery. Predicted REE was obtained from linear regression analysis of REE and fat free mass, in a group of 85 women, whose body mass index ranged between 20 and 60 kg/m(2). The deviation from predicted REE, calculated as area under the curve (AUC) over the 12-month period for each patient, was considered as the expression of energy economy. Energy economy AUC was significantly (P: < 0.005) negatively related to the weight lost during 12 months after surgery. Energy intake, calculated from self-reported food consumption, was also expressed as AUC. Energy intake AUC showed a significant (P: < 0.002) positive correlation with weight loss. Lipid oxidation rate, also calculated as AUC, significantly correlated, negatively, with energy economy (P: < 0. 001) and, positively, with energy intake (P: < 0.002). Preoperative leptin values were significantly (P: < 0.01) linked to individual energy economy capacity. In conclusion, after Roux-en-Y gastric bypass, energy economy hampers the weight loss process, probably through a low fat oxidation rate.

Energy, substrate and protein metabolism in morbid obesity before, during and after massive weight loss

OBJECTIVE

To investigate the effect of surgically induced weight loss on energy, substrate and protein metabolism of morbidly obese patients.

DESIGN

A prospective, clinical intervention study of morbidly obese patients before and after surgical treatment.

SUBJECTS

Eight morbidly obese patients (BMI 47.88+/-7.03).

METHODS

Total energy expenditure (TEE; doubly labeled water method), sleeping metabolic rate (SMR; respiration chamber), body composition (deuterium oxide component of doubly labeled water), substrate metabolism (48 h dietary records, 48 h urine collection and gaseous exchange in the respiration chamber) and whole body protein turnover (primed-continuous infusion of L-[1-13C]-leucine) were measured before, 3 and 12 months after vertical banded gastroplasty (VBG).

RESULTS

The TEE decreased as a result of a decreased SMR (64%) and non-SMR (36%; P=0.001). SMR as a function of fat-free mass (FFM) decreased after weight loss (P<0.05). The physical activity index (PAI), defined as TEE/SMR, was low and was not influenced by weight loss. Protein and carbohydrate oxidation decreased significantly after VBG (P<0.05), although 3 months after VBG protein oxidation did not decrease enough to prevent loss of FFM. The energy used for protein turnover was approximately 24% of SMR and did not change after weight loss.

CONCLUSIONS

Compensatory processes that oppose weight loss of morbidly obese patients exist, as demonstrated by the disproportional reduction of SMR, and a low PAI. Protein turnover is not a major contributor to the disproportional reduction of SMR.