Macronutrient (im)balance drives energy intake in an obesogenic food environment: An ecological analysis

Protein oxidation in non-exercising healthy adults under varying dietary conditions: Physiological determinants, effects on fuel partitioning, and implications for body weight regulation

BACKGROUND

Protein oxidation (PROTOX) typically accounts for the smallest fraction of daily energy expenditure (24hEE) in humans compared to carbohydrate and lipid oxidation. However, inter-individual differences in PROTOX may explain differences in fuel partitioning and body weight change. We aimed to elucidate the physiological determinants of PROTOX under controlled 24-h dietary conditions, including eucaloric feeding, fasting, and overfeeding diets with variable protein content.

METHODS

Eighty-six weight-stable healthy volunteers with normal glucose regulation (67 M/19F; age: 37 ± 10 years; BMI: 26.7 ± 4.5 kg/m2, body fat by DXA: 29.0 ± 9.8 %) underwent 24hEE measurements by whole-room calorimetry during energy balance (20 % protein, 50 % carbohydrate), different overfeeding diets (200 % of the daily eucaloric requirement), including three normal-protein (20 %) diets (balanced: 50 % carbohydrate; high-carbohydrate: 75 % carbohydrate; high-fat: 60 % fat), low-protein (3 %) and high-protein (30 %), and 24-h fasting in a randomized crossover design. Urine samples were collected during each 24-h dietary intervention for quantification of PROTOX and catecholamine excretion rates by nitrogen excretion and high-performance liquid chromatography, respectively.

RESULTS

PROTOX during energy balance (mean ± SD: 372 ± 78 kcal/day) was positively associated with protein intake (r = 0.39, p < 0.001), fat free mass (r = 0.35, p < 0.001), but not with fat mass (p = 0.24). Higher PROTOX was associated with higher 24-h urinary norepinephrine (partial r = 0.27, p = 0.01), but not epinephrine (p = 0.48), excretion rates. During normal-protein diets, higher PROTOX was associated with lower lipid oxidation, but showed no association with carbohydrate oxidation. Inter-individual variability in PROTOX did not predict changes in weight or body composition over two years.

CONCLUSION

Dietary protein content, lean body mass, and sympathetic nervous system activity are key determinants of PROTOX. Although PROTOX did not predict free-living weight gain, increased PROTOX is associated with decreased lipid oxidation, underscoring its role in fuel partitioning and whole-body energy and substrate balance.

Number of Remaining Teeth and Obesity in Chilean Older Adults

OBJECTIVES

To investigate whether the number of remaining teeth was associated with obesity among Chilean older people.

BACKGROUND

Contradictory findings on the associations between cumulative tooth loss, chewing discomfort and the consumption of fruits and vegetables in older people have been reported; moreover, findings on the relationship between dentition and nutritional status are inconsistent. The latter has been studied in some Latin American countries, but no data have been reported for Chile.

MATERIALS AND METHODS

We undertook a secondary analysis of clinical and self-reported data from a national survey of adults-the Chilean National Health Survey 2016-17 or 2016-17 (NHS)-to examine associations between the number of remaining teeth (defined both as the presence of a functional dentition and as ordinal categories of the number of remaining teeth: ≥ 20, 10-19, 1-9 or 0 teeth) and obesity (BMI ≥ 30.0 kg/m2) among non-institutionalised older adults aged ≥ 65 years. Associations between the number of remaining teeth and (a) chewing discomfort and (b) daily consumption of fruits and vegetables were also examined. Multivariate models for obesity and functional dentition or dentition status were adjusted for sex, age, education level, residency and denture use. Analyses used Stata, applying survey weighting to obtain population estimates.

RESULTS

Data from n = 1363 non-institutionalised older adults aged ≥ 65 years, representing a population of 1,765,340 individuals was analysed. A minority of the sample had a functional dentition (22.5%), which was more common in men (28.7%) and among urban residents (24.8%). A consistent gradient in functional dentition was observed by educational level, with prevalence rates of 7.2%, 27.2% and 76.8% among individuals of low, medium and high education level, respectively. More than one in 10 individuals (12.4% of the sample) reported chewing discomfort, and this was more common among those who had (14.9%) than for those who did not have a functional dentition (6.5%). Individuals with a functional dentition consumed more fruits and vegetables daily than those with fewer than 20 teeth. Regarding the study outcome, 35.6% of participants were obese. Obesity was more common among those who did not have a functional dentition (37.3%) than for those who did (30.2%). In the multivariate model, the lack of a functional dentition (having fewer remaining teeth) was not associated with obesity (PR 1.06; 95% CI 0.86, 1.32). Similar findings were observed when examining associations by dentition status categories (10-19 teeth: PR 1.13; 95% CI 0.9, 1.41, 1-9 teeth: PR 1.07; 0.84, 1.35, edentulous: PR 0.88; 95% CI 0.68, 1.13. using ≥ 20 teeth as ref.).

CONCLUSION

The lack of a functional dentition (having fewer remaining teeth) was associated with lower daily fruit and vegetable consumption and chewing discomfort but not with obesity in this population.

Maternal protein intake during pregnancy and obesity risk in mothers and offspring: a prospective cohort study

BACKGROUND

The optimal dietary macronutrient composition during pregnancy to mitigate obesity risk in mothers and offspring remains unclear.

OBJECTIVES

This study aims to assess associations between maternal dietary macronutrient composition and obesity outcomes in mothers and offspring.

METHODS

We analyzed 66,360 singleton pregnancies from the Danish National Birth Cohort, with dietary intake assessed at gestational week 25. Outcomes included maternal postpartum weight retention (PPWR) at 6 and 18 mo and offspring's birth weight, risks of small for gestational age (SGA) and large for gestational age (LGA), body mass index (BMI) z-scores, and overweight/obesity (OWOB) risk at ages 7, 11, and 14 y. Mixture models with response surface visualization examined interactive macronutrient associations, and mixed restricted cubic splines assessed potential nonlinear relationships between maternal protein intake and obesity outcomes.

RESULTS

Mean maternal macronutrient compositions were 15.2% protein, 30.2% fat, and 54.1% carbohydrate. Response surfaces revealed that maternal lower protein intake (%), diluted by higher fat and/or carbohydrate, was associated with higher maternal PPWR at 6 and 18 mo but lower birth weight and BMI z-scores in offspring at ages 7, 11, and 14 y. Mixed restricted cubic splines indicated nonlinear associations between maternal protein intake (%) and SGA risk (nonlinear P = 0.003) and LGA (nonlinear P = 0.04), with a threshold around 15% protein; below this, SGA risk increased whereas LGA risk decreased. Linear associations were observed for risks of substantial PPWR (PPWR >5 kg) and childhood OWOB risk (nonlinear P > 0.05). Each 5% higher protein intake during pregnancy was related to a lower risk of substantial PPWR at 6 mo (odds ratio: 0.90; 95% confidence interval: 0.85, 0.95) and 18 mo (0.88; 0.82, 0.94) but higher risks of OWOB at ages 7 y (1.07; 1.01, 1.15) and 11 y (1.11; 1.03, 1.18), with no association at 14 y (1.02; 0.95, 1.10).

CONCLUSIONS

Higher maternal protein intake during pregnancy was associated with lower PPWR and SGA risk but higher LGA and childhood OWOB risks, highlighting potential trade-offs in maternal and offspring obesity outcomes.

Rapid benefits in older age from transition to whole food diet regardless of protein source or fat to carbohydrate ratio: Arandomised control trial

Plant-based diets reduces the risk of chronic conditions. The interaction between protein source and other macronutrients-fat (F) and carbohydrate (C)-has yet to be investigated. The aim was to assess the main and interactive effects of protein-source (plant vs. animal) and F:C (high or low) and the transition from an Australian diet to a whole food diet on various health markers in older individuals. This single-blinded, parallel, randomised experimental trial used a 2 × 2 factorial design to compare pro-vegetarian (70:30 plant to animal) versus omnivorous (50:50 plant to animal) diets at 14% protein and varying fat-to-carbohydrate ratios (high fat ~40% vs. low fat ~30%) over 4 weeks. Study foods were provided, alcohol consumption was discouraged, and dietary intake was determined through food records. Analysis included both RCT and observational data. Changes in appetite, palatability of diets, and dietary intake were assessed. Body composition, muscle strength, function, gut microbiome, and cardiometabolic health parameters were measured. Data from 113 (of the 128 randomised) individuals aged 65-75 years were analysed. Pro-vegetarian diets reduced diastolic blood pressure, total cholesterol and glucose levels. Moreover, the overall sample exhibited increased short-chain fatty acids and FGF21 levels, as well as improvements in body composition, function, and cardio-metabolic parameters irrespective of dietary treatment. Transitioning to a diet rich in fruit, vegetables, fibre, and moderate protein was associated with improved health markers in older age, with added benefits from pro-vegetarian diets. Further research on long-term effects is needed.

Asian Low-Carbohydrate Diet with Increased Whole Egg Consumption Improves Metabolic Outcomes in Metabolic Syndrome: A 52-Week Intervention Study

BACKGROUND

The low-carbohydrate-ketogenic diet, an effective strategy to address metabolic syndrome (MetS) and obesity has raised concerns about high-fat consumption on atherogenic lipoproteins.

OBJECTIVE

The aim of this study was to compare the Asian ketogenic diet (AKD), which incorporates balanced protein and fat intake from Asian foods, with a balanced low-caloric diet (BLC) in individuals diagnosed with MetS.

METHODS

A 52-wk randomized clinical trial included 3 parallel groups: AKD with increased whole egg intake [egg yolk Asian ketogenic diet (Yolk-AKD, n = 28)], yolk-free ketogenic diet with egg white supplementation [egg white Asian ketogenic diet (White-AKD, n = 26)], and BLC (n = 22). Primary outcomes were anthropometric and metabolic changes.

RESULTS

The AKD groups achieved significant reductions in weight and waist circumference (P < 0.05). Compared with the BLC group, the AKD groups demonstrated significant improvements in insulin resistance at week 6 and in triglyceride concentrations at weeks 12 (Yolk-AKD) and 35 (White-AKD) (P < 0.05). The AKD groups experienced improvements in hormones associated with insulin sensitivity and appetite, whereas only the Yolk-AKD group had a significant decrease in inflammation-related hormones (P < 0.05). From weeks 35-52, the AKD maintained reductions in anthropometric measurements, blood pressure, improved glucose tolerance, enhanced lipid profiles, and better liver function compared with the BLC.

CONCLUSIONS

The AKD proved safe and effective, yielding various metabolic improvements in individuals with MetS compared with the BLC. Emphasizing a low-saturated fat diet while disregarding dietary cholesterol, this approach holds promise for MetS and obesity management. The inclusion of both White-AKD and Yolk-AKD groups allowed for a comprehensive assessment of the AKD's impact, elucidating the differential effects of whole egg consumption on metabolic outcomes. Further studies are warranted. This trial was registered at clinicaltrials.gov as NCT04608136.

Macronutrient composition of plant-based diets and breast cancer risk: the E3N prospective cohort study

PURPOSE

Recent evidence suggests that plant-based diets may reduce the risk of breast cancer (BC). However, the macronutrient composition of plant-based diets and its potential impact on BC risk has not been well explored. This analysis investigated the association of macronutrient composition with BC risk across a spectrum of plant-based diet indexes using a multidimensional approach.

DESIGN

This study followed 64,655 participants from the Etude Epidémiologique auprès de femmes de la Mutuelle Générale de l'Education Nationale (E3N) cohort from 1993 to 2014. Diets were evaluated using validated 208-item diet history questionnaires at baseline (1993) and follow-up (2005), to calculate adherence to the overall plant-based diet (PDI), healthful plant-based diet (hPDI), and unhealthful plant-based diet (uPDI). The association of macronutrient composition with BC risk was assessed via generalized additive time-dependent Cox models across different levels of these indexes. Response surfaces were generated to visualize compositional associations at the 25th, 50th, and 75th percentile of each index (low, moderate, and high).

RESULTS

A total of 3,932 incident BC cases were identified during the 21-year follow-up. There was a significant association between macronutrient composition and BC risk for hPDI, uPDI, and PDI (all P < 0.001). Akaike information criterion favored the hPDI model for characterizing the association between macronutrients and BC. BC risk was highest for individuals with a lower hPDI score who also consumed a diet containing lower protein (10%), lower carbohydrate (35%), and higher fat (55%). The lowest risk of BC was observed in those with higher hPDI scores with the lowest intake of protein (10%). At higher PDI and uPDI, diets containing higher protein (30%) and fat (45%) had the highest BC risk.

CONCLUSION

These results demonstrate a complex relationship between macronutrient composition, plant-based diet quality, and BC risk. Further research is needed to examine specific foods that may be driving these associations.

REGISTRY

The protocol is registered at clinicaltrials.gov as NCT03285230.

Sucrose overconsumption impairs AgRP neuron dynamics and promotes palatable food intake

Rapid gut-brain communication is critical to maintain energy balance and is disrupted in diet-induced obesity. In particular, the role of carbohydrate overconsumption in the regulation of interoceptive circuits in vivo requires further investigation. Here, we report that an obesogenic high-sucrose diet (HSD) selectively blunts silencing of hunger-promoting agouti-related protein (AgRP) neurons following intragastric delivery of glucose, whereas we previously showed that overconsumption of a high-fat diet (HFD) selectively attenuates lipid-induced neural silencing. By contrast, both HSD and HFD reversibly dampen rapid AgRP neuron inhibition following chow presentation and promote intake of more palatable foods. Our findings reveal that excess sugar and fat pathologically modulate feeding circuit activity in both macronutrient-dependent and -independent ways and thus may additively exacerbate obesity.

Evidence for the protein leverage hypothesis in preschool children prone to obesity

BACKGROUND & AIMS

The protein leverage hypothesis (PLH) proposed that strict regulation of protein intake drives energy overconsumption and obesity when diets are diluted by fat and/or carbohydrates. Evidence about the PLH has been found in adults, while studies in children are limited. Thus, we aimed to test the PLH by assessing the role of dietary protein on macronutrients, energy intake, and obesity risk using data from preschool children followed for 1.3 years.

METHODS

553 preschool children aged 2-6 years from the 'Healthy Start' project were included.

EXPOSURES

The proportion of energy intake from protein, fat, and carbohydrates collected from a 4-day dietary record.

OUTCOMES

Energy intake, BMI z-score, fat mass (FM) %, waist- (WHtR) and hip-height ratio (HHtR). Power function analysis was used to test the leverage of protein on energy intake. Mixture models were used to explore interactive associations of macronutrient composition on all these outcomes, with results visualized as response surfaces on the nutritional geometry.

RESULTS

Evidence for the PLH was confirmed in preschool children. The distribution of protein intake (% of MJ, IQR: 3.2) varied substantially less than for carbohydrate (IQR: 5.7) or fat (IQR: 6.3) intakes, suggesting protein intake is most tightly regulated. Absolute energy intake varied inversely with dietary percentage energy from protein (L = -0.14, 95% CI: -0.25, -0.04). Compared to children with high fat or carbohydrate intakes, children with high dietary protein intake (>20% of MJ) had a greater decrease in WHtR and HHtR over the 1.3-year follow-up, offering evidence for the PLH in prospective analysis. But no association was observed between macronutrient distribution and changes in BMI z-score or FM%.

CONCLUSIONS

In this study in preschool children, protein intake was the most tightly regulated macronutrient, and energy intake was an inverse function of dietary protein concentration, indicating the evidence for protein leverage. Increases in WHtR and HHtR were principally associated with the dietary protein dilution, supporting the PLH. These findings highlight the importance of protein in children's diets, which seems to have significant implications for childhood obesity risk and overall health.

Protein and amino acids in obesity: friends or foes?

PURPOSE OF REVIEW

Nutritional interventions using protein and amino acids in obesity are popular therapeutical strategies to limit obesity development. However, the effects of dietary protein intake and amino acid metabolic alterations involved in obesity pathophysiology have not been completely unravelled. Significant recent studies have brought to light new findings in these areas, which are the primary focus of this review.

RECENT FINDINGS

We describe the effects of protein intake on weight regain prevention, the influence on gut microbiota, the response to low-protein highly processed foods, and the contrasting impacts of a high-protein diet on adults and children. We also explore newly discovered correlations between amino acids, liver fat accumulation, and the dysregulation of the liver-pancreas axis due to alterations in amino acid levels in the context of obesity. Lastly, we consider branched-chain amino acids, along with glycine and tryptophan, as significant biomarkers during periods of positive or negative energy balance.

SUMMARY

Interventions using dietary protein in obesity may be useful, especially during energy restriction but also in sarcopenic obesity. Furthermore, metabolic profiles that encompass alterations in certain amino acids can provide valuable insights into the metabolic condition of patients with obesity, particularly in relation to insulin resistance and the risk of developing type 2 diabetes.

Protein appetite as an integrator in the obesity system: the protein leverage hypothesis

Despite the large volume and extensive range of obesity research, there is substantial disagreement on the causes and effective preventative strategies. We suggest the field will benefit from greater emphasis on integrative approaches that examine how various potential contributors interact, rather than regarding them as competing explanations. We demonstrate the application of nutritional geometry, a multi-nutrient integrative framework developed in the ecological sciences, to obesity research. Such studies have shown that humans, like many other species, regulate protein intake more strongly than other dietary components, and consequently if dietary protein is diluted there is a compensatory increase in food intake-a process called protein leverage. The protein leverage hypothesis (PLH) proposes that the dilution of protein in modern food supplies by fat and carbohydrate-rich highly processed foods has resulted in increased energy intake through protein leverage. We present evidence for the PLH from a variety of sources (mechanistic, experimental and observational), and show that this mechanism is compatible with many other findings and theories in obesity research. This article is part of a discussion meeting issue 'Causes of obesity: theories, conjectures and evidence (Part II)'.

Testing for Protein Leverage in Patients with Gastric Bypass: A Pilot Study

INTRODUCTION

Protein leverage (PL) is the phenomenon whereby a dominant appetite for protein drives overconsumption of energy with a decline in the ratio of protein to fat and carbohydrate in the diet. PL has been independently verified in several randomized control trials, and its predictions are supported by diet surveillance data. Our aim in the present study was to test whether surgical intervention through gastric bypass will ameliorate the PL effect.

METHODS

Ten patients with gastric bypass (2-5 years postsurgical time) were given ad libitum access to study food comprising 10%, 15%, or 25% protein and no access to other foods for 3 days while controlling food palatability and variety. Food intake was measured, and energy and nutrient intakes were calculated. Body weight, blood chemistry, lipid profile, hormones (insulin, leptin, and ghrelin), and creatinine were determined before and after each experimental period.

RESULTS

The gastric bypass patients in our study did not show evidence for protein intake regulation as predicted under PL but ate to constant total energy intake on the 10%, 15%, and 25% protein diets with protein intake varying significantly. Patients lost weight in the three study periods, but significant weight loss was observed only on the 15% protein diet.

CONCLUSION

Our results suggest that gastric bypass might disengage the PL mechanism, thus ameliorating an appetite-specific mechanism that drives energy overconsumption in modern food environments.

No strong evidence of the protein leverage hypothesis in pregnant women with obesity and their infants

OBJECTIVE

The goal of this study was to investigate the role of dietary protein on macronutrient and energy intake, maternal adiposity during pregnancy, and infant adiposity at birth.

METHODS

In 41 women with obesity, early-pregnancy (13-16 weeks) protein intake was assessed with food photography and expressed as a ratio of Estimated Average Requirements (EAR) in pregnancy for protein (0.88 g/kg/d), herein "protein balance." Energy intake was measured by the intake-balance method, gestational weight gain as grams per week, and fat mass by a three-compartment model. Spearman correlations and linear models were computed using R version 4.1.1 (p < 0.05 considered significant).

RESULTS

Women had a mean (SD) age of 27.5 (4.8) years and a pregravid BMI of 34.4 (2.9), kg/m2 , and the majority were non-White (n = 23, 56.1%). Protein balance in early pregnancy was not significantly associated with energy intake across mid and mid/late pregnancy (β = 328.7, p = 0.30 and β = 286.2, p = 0.26, respectively) or gestational weight gain (β = 117.0, p = 0.41). Protein balance was inversely associated with fat mass in early, mid, and late pregnancy (β = -10.6, p = 0.01, β = -10.4, p = 0.03, β = -10.3, p = 0.03, respectively). Protein balance did not predict infant adiposity at birth (p > 0.05).

CONCLUSIONS

Low protein intake may have been present before pregnancy, explaining early relationships with adiposity in this cohort. The protein leverage hypothesis is likely not implicated in the intergenerational transmission of obesity.