Selections from current literature: effects of dieting and exercise on resting metabolic rate and implications for weight management

Tissue losses and metabolic adaptations both contribute to the reduction in resting metabolic rate following weight loss

OBJECTIVE

To characterize the contributions of the loss of energy-expending tissues and metabolic adaptations to the reduction in resting metabolic rate (RMR) following weight loss.

METHODS

A secondary analysis was conducted on data from the Comprehensive Assessment of Long-term Effects of Reducing Intake of Energy study. Changes in RMR, body composition, and metabolic hormones were examined over 12 months of calorie restriction in 109 individuals. The contribution of tissue losses to the decline in RMR was determined by weighing changes in the size of energy-expending tissues and organs (skeletal muscle, adipose tissue, bone, brain, inner organs, residual mass) assessed by dual-energy X-ray absorptiometry with their tissue-specific metabolic rates. Metabolic adaptations were quantified as the remaining reduction in RMR.

RESULTS

RMR was reduced by 101 ± 12 kcal/d as participants lost 7.3 ± 0.2 kg (both p < 0.001). On average, 60% of the total reduction in RMR were explained by energy-expending tissues losses, while 40% were attributed to metabolic adaptations. The loss of skeletal muscle mass (1.0 ± 0.7 kg) was not significantly related to RMR changes (r = 0.14, p = 0.16), whereas adipose tissue losses (7.2 ± 3.0 kg) were positively associated with the reduction in RMR (r = 0.42, p < 0.001) and metabolic adaptations (r = 0.31, p < 0.001). Metabolic adaptations were correlated with declines in leptin (r = 0.27, p < 0.01), triiodothyronine (r = 0.19, p < 0.05), and insulin (r = 0.25, p < 0.05).

CONCLUSIONS

During weight loss, tissue loss and metabolic adaptations both contribute to the reduction in RMR, albeit variably. Contrary to popularly belief, it is not skeletal muscle, but rather adipose tissue losses that seem to drive RMR reductions following weight loss. Future research should target personalized strategies addressing the predominant cause of RMR reduction for weight maintenance.

Specific amino acids but not total protein attenuate postpartum weight gain among Hispanic women from Southern California

There is a high prevalence of obesity and type 2 diabetes in the United States, particularly among Hispanic women, which may be partly explained by failure to lose gestational weight during the postpartum period. Previous work indicates that protein and amino acids may protect against weight gain; therefore, this study examined the impact of dietary protein and amino acid intake on changes in postpartum weight and the percent of women meeting the Estimated Average Requirement (EAR) for these dietary variables among Hispanic women from the Southern California Mother's Milk Study (n = 99). Multivariable linear regression analysis was used to examine the associations between protein and amino acid intake with change in weight after adjusting for maternal age, height, and energy intake. Women's weight increased from prepregnancy to 1-month and 6-months postpartum (71.1 ± 14.6 vs. 73.1 ± 13.1 vs. 74.5 ± 14.6 kg, p < .0001). Although dietary protein was not associated with weight change (β = -1.09; p = .13), phenylalanine (β = -1.46; p = .04), tryptophan (β = -1.71; p = .009), valine (β = -1.34; p = .04), isoleucine (β = -1.26; p = .045), and cysteine (β = -1.52; p = .02) intake were inversely associated with weight change. Additionally, fewer women met the EAR values for cysteine (11.1%), phenylalanine (60.6%), and methionine (69.7%), whereas most women met the EAR values for tryptophan (92.9%), valine (96.0%), and isoleucine (94.9%). Study results indicate that several essential and conditionally essential amino acids were associated with postpartum weight loss, with a significant portion of women not meeting recommended intake levels for some of these amino acids. These results highlight the importance of postpartum maternal diet as a potential modifiable risk factor.

Effect of Intermittent Fasting on Non-Alcoholic Fatty Liver Disease: Systematic Review and Meta-Analysis

Background: Weight loss by lifestyle modification is the cornerstone therapy of non-alcoholic fatty liver disease (NAFLD). Intermittent fasting has shown favorable effects on body weight (BW) and relevant indicators of NAFLD in several reports. Objective: To estimate the effects of intermittent fasting on adults with NAFLD. Materials and methods: Literature searches were conducted on PubMed, EMBASE, Web of Science, Cochrane Library, and ClinicalTrials.gov from inception to May 10, 2021. Results: A total of six studies involving 417 patients with NAFLD were included. In the meta-analysis, there were significant differences in BW, body mass index (BMI), alanine aminotransferase (ALT), and aspartate transaminase (AST) between the control and fasting group. Up to now, there is no significant difference in triglycerides (TG), total cholesterol (TC), and other metabolic parameters between the two groups. Conclusions: Intermittent fasting is beneficial for weight management and liver enzyme improvement, but long-term feasibility and safety of intermittent fasting should be conducted in further studies.

Predicting Equations and Resting Energy Expenditure Changes in Overweight Adults

Introduction

The aim of the study is to show the differences between the measured and estimated values of resting energy expenditure and any changes occurring after the 6-month weight loss intervention program.

Methods

We included 33 healthy adults aged 25–49 years with an average body mass index 29.1±2.7 kg/m 2 for female and 29.8±2.8 kg/m² for male. The measured resting energy expenditure was obtained by indirect calorimeter MedGem® Microlife and estimated resting energy expenditure by the Harris–Benedict equation, the Mifflin–St Jeor equation, the Owen equation, the Wright equation, and by the Tanita body composition analyser. All measurements and calculations were carried out before and after the 6-month intervention. Results were compared using paired t-tests. P value less than 0.05 was considered statistically significant.

Results

A comparison of the measured resting energy expenditure of female subjects with the estimated resting energy expenditure using the Harris–Benedict equation, the Mifflin–St Jeor equation and the Wright equation showed a statistically significant difference. A comparison of the measured resting energy expenditure of male subjects with the estimated resting energy expenditure using the Harris–Benedict equation and the Wright equation showed a statistically significant difference. There was a significant difference in the measured resting energy expenditure and estimated resting energy expenditure using Tanita.

Conclusions

We concluded that the most comparable equation for our sample was the Owen’s equation. After losing weight, the measured resting energy expenditure has decreased, which must be taken into account in further diet therapy.

One-year caloric restriction and 12-week exercise training intervention in obese adults with type 2 diabetes: emphasis on metabolic control and resting metabolic rate

PURPOSE

The effect of combined lifestyle interventions (LSI) including dietary and physical activity on metabolic health, energy metabolism and VO₂max in diabetic patients has provided mixed results. We evaluated the impact of 1-year caloric restriction (CR), and 12-week supervised structured exercise training (SSET) on metabolic health, RMR and VO₂max in obese adults with type 2 diabetes.

METHODS

After 1-month education for LSI, 33 participants had anthropometric, biochemical and metabolic assessments. They then started CR based on RMR, and 3-month SSET during the months 1-3 (Early-SSET) or 4-6 (Late-SSET). Reassessments were planned after 3, 6 and 12 months. Using a per-protocol analysis, we evaluated parameter changes from baseline and their associations for the 23 participants (11 Early-SSET, 12 Late-SSET) who completed the study. RMR was adjusted (adjRMR) for age, sex, fat-free mass (FFM) and fat mass (FM).

RESULTS

Compared with baseline, after 6 months we found significant increases in VO₂max (+ 14%) and HDL-cholesterol (+ 13%), and reduction in body mass index (- 3%), FM (- 8%) and glycated hemoglobin (HbA1c, - 7%). Training-related caloric expenditure negatively correlated with changes in body weight (p < 0.001), FM (p < 0.001) and HbA1c (p = 0.006). These results were confirmed at the 12-month follow-up. Pooling together all follow-up data, adjRMR changes correlated with changes in glycemia (r = 0.29, p = 0.02), total-cholesterol (r = 0.29, p = 0.02) and VO₂max (r = - 0.26,p = 0.02). No significant differences emerged between the Early- and Late-SSET groups.

CONCLUSIONS

Combined intervention with SSET and CR improved metabolic control. Changes in metabolic health and fitness correlated with changes of adjRMR, which was reduced improving fitness, glycemia and cholesterolemia.

CLINICAL TRIAL REGISTRY

Trial registration number: NCT03785379. URL of registration: http://clinicaltrials.gov .

Lifestyle Intervention Program for Amelioration of Dysmetabolism in Overweight Women

Overweight and obesity, a cluster of multiple risk factors for atherosclerosis such as elevated blood pressure, elevated glucose level, and dyslipidemia, increase the risk of all-cause mortality and cardiovascular morbidity and mortality. Physical activity and a proper diet are essential preventive measures. The aim of the study was to evaluate the effects of a two-month intervention program consisting of a low-caloric diet (1,500 kcal) and increased physical activity on the anthropometric parameters, body composition, resting metabolic rate, and maximum oxygen uptake. The study was conducted in 22 women aged 20-38 with diagnosed overweight or obesity. We found that after completing the eight-week-long intervention program, there were significant changes in body composition, consisting of a smaller proportion of body fat and increased lean body mass. Further, we observed a decrease in body weight by 4.3 ± 2.5 kg (p < 0.01), a reduction in waist and hip circumference of 2.6 ± 4.5 cm (p < 0.01) and 4.4 ± 2.9 cm (p < 0.01), respectively, and an increase in maximum oxygen uptake by about 5.2 ± 8.4 ml/kg/min (p < 0.01). We conclude that the intervention program consisting of counseling on diet and physical activity may be highly motivational for patients with excess body weight and care givers should give it a try before commencing more aggressive psychopharmacological therapies.

Effects of an Ad Libitum Consumed Low-Fat Plant-Based Diet Supplemented with Plant-Based Meal Replacements on Body Composition Indices

Objective. To document the effect of a diet free from animal-sourced nutrients on body composition indices. Methods. This was a nonrandomized interventional (n = 241)-control (n = 84) trial with a 10-week, low-fat, plant-based diet supplemented with two daily meal replacements. The meals were allowed to be eaten to full satiety without prespecified calorie restrictions. Control subjects received weekly lectures on the rationale and expected benefits of plant-based nutrition. Body composition indices were measured with bioimpedance analysis. Results. Relative to controls, in cases, postintervention body fat percentage was reduced by 4.3 (95% CI 4.1–4.6)% points (a relative decrement of −13.4%), visceral fat by 1.6 (95% CI 1.5–1.7) fat cross-sectional surface units, and weight by 5.6 kg (95% CI 5.2–6), while muscle mass was reduced by 0.3 kg (95% CI 0.06–0.5) with a relative increase of muscle mass percentage of 4.2 (3.9–4.4)% points. Analysis of covariance showed significantly larger adjusted fat reductions in cases compared to controls. Late follow-up revealed further weight loss in 60% of cases and no significant change in controls. Conclusions. Low-fat, plant-based diet in free-living nonresidential conditions eaten ad libitum enables significant and meaningful body fat reductions with relative preservation of muscle mass. This trial is registered with NCT02906072, ClinicalTrials.gov.

Obese Patients with Type 2 Diabetes on Conventional Versus Intensive Insulin Therapy: Efficacy of Low-Calorie Dietary Intervention

INTRODUCTION

The aim of this prospective study was to assess the results of a standard low-calorie dietary intervention (7.5 MJ/day) on body weight (BW) and the metabolic profile of obese patients with type 2 diabetes mellitus (T2DM) on intensive insulin therapy (IIT: 4 insulin injections/day) versus conventional insulin therapy (CIT: 2/3 insulin injections/day).

METHODS

A total of 60 patients (n = 60, 23 males and 37 postmenopausal females) were recruited and categorized into two groups according to the scheme of insulin treatment. Thirty were on IIT (13 males and 17 females) and an equal number on CIT (10 males and 20 females). BW, body mass index (BMI), HbA1c, and metabolic parameters were compared at 6 and 12 months after baseline.

RESULTS

Significant reductions were observed in the BW, BMI, HbA1c (p ≤ 0.001 for all) and cholesterol (p ≤ 0.05) at 6 months post-intervention. At 1 year, median BW reduction was 4.5 kg (3.3, 5.8) for patients on IIT and 4.8 kg (3.6, 7.0) for those on CIT. The 12-month dietary intervention increased prevalence of normoglycemia in the IIT group and reduced the prevalence of obesity prevalence among the CIT participants (all p < 0.001). CIT patients with BW reduction ≥5.0% demonstrated 11-fold greater chances of being normoglycemic (odds ratio 11.3, 95% CI 1.1-110.5). BW reduction ≥7.0% was associated with CIT, being overweight, and having normal HDLc, LDLc, and cholesterol levels. A reduction in BW between 5.0% and 6.9% was associated with IIT, normoglycemia, and obesity.

CONCLUSION

A 12-month 1800-kcal dietary intervention achieved significant BW and HbA1c reductions irrespectively of insulin regimen. CIT was associated with BW reduction greater than 8.0%, whereas IIT was associated with higher rates of normoglycemia.

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.

Caloric expenditure in the morbidly obese using dual energy X-ray absorptiometry

Total caloric expenditure is the sum of resting energy expenditure (REE) and caloric expenditure during physical activity. In this study, we examined total caloric expenditure in 25 morbidly obese patients (body mass index>or=35 kg/m(2)) using dual energy X-ray absorptiometry (DXA) scanning and cardiorespiratory exercise testing. Our results show average REE for all individuals was 2027+/-276 kcal/d and mean net caloric expenditure during 30 min of exercise was 115+/-16 kcals. Assuming the mean of all input values, a strict 1500 kcal/d diet combined with 150 min per wk of structured physical activity, the projected weight change was -7% (8.8+/-6.2 kg) for 6 mo. We conclude that morbidly obese individuals should be able to achieve only a modest weight loss by following minimal national guidelines. These data suggest that more aggressive energy expenditure and caloric restriction targets for long periods of time are needed to result in significant weight loss in this population.