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Effects of Intermittent Energy Restriction Compared with Those of Continuous Energy Restriction on Body Composition and Cardiometabolic Risk Markers - A Systematic Review and Meta-Analysis of Randomized Controlled Trials in Adults.
Schroor, MM, Joris, PJ, Plat, J, Mensink, RP
Advances in nutrition (Bethesda, Md.). 2024;15(1):100130
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Intermittent energy restriction (IER) diets, such as the 5:2 diet, time-restricted eating (TRE), and alternate-day fasting (ADF), are gaining popularity. According to previous research, IER protocols effectively manage obesity and may have many other health benefits, including improving metabolic health. This systematic review and meta-analysis of twenty-eight parallel-design randomised controlled trials looked at the benefits of IER protocols, such as ADF, TRE, and the 5:2 diet, and the effects of continuous energy restriction (CER) on anthropometric and cardiometabolic outcomes. The results of this systematic review and meta-analysis showed that both the IER and CER are equally beneficial. However, IER protocols showed greater but clinically insignificant improvements in fat-free mass and waist circumference in healthy adults. IER and CER protocols were not different in improving the lipid profile, glucose and insulin levels and blood pressure. Different IER diets showed different positive effects on metabolic parameters. Future robust studies are required to assess the effects of these energy-restriction diets on metabolic and anthropometric parameters because of the high variability in the included studies. However, healthcare professionals can use the results of this review to understand the potential clinical utility of various energy-restriction diets.
Abstract
The interest in intermittent energy restriction (IER) diets as a weight-loss approach is increasing. Different IER protocols exist, including time-restricted eating (TRE), alternate-day fasting (ADF), and the 5:2 diet. This meta-analysis compared the effects of these IER diets with continuous energy restriction (CER) on anthropometrics and cardiometabolic risk markers in healthy adults. Twenty-eight trials were identified that studied TRE (k = 7), ADF (k = 10), or the 5:2 diet (k = 11) for 2-52 wk. Energy intakes between intervention groups within a study were comparable (17 trials), lower in IER (5 trials), or not reported (6 trials). Weighted mean differences (WMDs) were calculated using fixed- or random-effects models. Changes in body weight [WMD: -0.42 kg; 95% confidence interval (CI): -0.96 to 0.13; P = 0.132] and fat mass (FM) (WMD: -0.31 kg; 95% CI: -0.98 to 0.36; P = 0.362) were comparable when results of the 3 IER diets were combined and compared with those of CER. All IER diets combined reduced fat-free mass (WMD: -0.20 kg; 95% CI: -0.39 to -0.01; P = 0.044) and waist circumference (WMD: -0.91 cm; 95% CI: -1.76 to -0.06; P = 0.036) more than CER. Effects on body mass index [BMI (kg/m2)], glucose, insulin, homeostatic model assessment for insulin resistance (HOMA-IR), serum lipid and lipoprotein concentrations, and blood pressure did not differ. Further, TRE reduced body weight, FM, and fat-free mass more than CER, whereas ADF improved HOMA-IR more. BMI was reduced less in the 5:2 diet compared with CER. In conclusion, the 3 IER diets combined did not lead to superior improvements in anthropometrics and cardiometabolic risk markers compared with CER diets. Slightly greater reductions were, however, observed in fat-free mass and waist circumference. To what extent differences in energy intakes between groups within studies may have influenced these outcomes should be addressed in future studies.
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Nutrition and Exercise Interventions to Improve Body Composition for Persons with Overweight or Obesity Near Retirement Age: A Systematic Review and Network Meta-Analysis of Randomized Controlled Trials.
Eglseer, D, Traxler, M, Embacher, S, Reiter, L, Schoufour, JD, Weijs, PJM, Voortman, T, Boirie, Y, Cruz-Jentoft, A, Bauer, S
Advances in nutrition (Bethesda, Md.). 2023;14(3):516-538
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Obesity is characterised by excessive fat accumulation that often occurs during the process of aging. Aging is accompanied not only by a gradual increase in body fat stores but also a decrease in muscle mass, muscle function, and water retention. The aim of this study was to assess which nutrition and exercise interventions are most effective for improving the body composition (fat mass and muscle mass), body mass index, and waist circumference in persons with overweight or obesity near retirement age (55 to 70 years of age). This study was a systematic review and network meta-analysis (NMA) of randomised controlled trials of sixty-six studies. Results of the NMA showed that the most effective strategy to improve body composition, i.e., losing fat without increasing risk of sarcopenia in persons with obesity around retirement age, was combining energy restriction with resistance training or with mixed exercise (resistance combined with aerobic exercise) and/or high-protein intake. In fact, without training, an energy-restricted diet with or without added protein helped individuals lose fat mass but also tended to result in losses of muscle mass. Authors conclude that an energy-restricted diet alone probably contributes to the development of sarcopenic obesity in persons of retirement age. Thus, to simultaneously lose weight and maintain muscle mass, authors recommend a combination of energy restriction and resistance training.
Abstract
The retirement phase is an opportunity to integrate healthy (nutrition/exercise) habits into daily life. We conducted this systematic review to assess which nutrition and exercise interventions most effectively improve body composition (fat/muscle mass), body mass index (BMI), and waist circumference (WC) in persons with obesity/overweight near retirement age (ages 55-70 y). We conducted a systematic review and network meta-analysis (NMA) of randomized controlled trials, searching 4 databases from their inception up to July 12, 2022. The NMA was based on a random effects model, pooled mean differences, standardized mean differences, their 95% confidence intervals, and correlations with multi-arm studies. Subgroup and sensitivity analyses were also conducted. Ninety-two studies were included, 66 of which with 4957 participants could be used for the NMA. Identified interventions were clustered into 12 groups: no intervention, energy restriction (i.e., 500-1000 kcal), energy restriction plus high-protein intake (1.1-1.7 g/kg/body weight), intermittent fasting, mixed exercise (aerobic and resistance), resistance training, aerobic training, high protein plus resistance training, energy restriction plus high protein plus exercise, energy restriction plus resistance training, energy restriction plus aerobic training, and energy restriction plus mixed exercise. Intervention durations ranged from 8 wk to 6 mo. Body fat was reduced with energy restriction plus any exercise or plus high-protein intake. Energy restriction alone was less effective and tended to decrease muscle mass. Muscle mass was only significantly increased with mixed exercise. All other interventions including exercise effectively preserved muscle mass. A BMI and/or WC decrease was achieved with all interventions except aerobic training/resistance training alone or resistance training plus high protein. Overall, the most effective strategy for nearly all outcomes was combining energy restriction with resistance training or mixed exercise and high protein. Health care professionals involved in the management of persons with obesity need to be aware that an energy-restricted diet alone may contribute to sarcopenic obesity in persons near retirement age. This network meta-analysis is registered at https://www.crd.york.ac.uk/prospero/ as CRD42021276465.
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Intermittent Fasting versus Continuous Calorie Restriction: Which Is Better for Weight Loss?
Zhang, Q, Zhang, C, Wang, H, Ma, Z, Liu, D, Guan, X, Liu, Y, Fu, Y, Cui, M, Dong, J
Nutrients. 2022;14(9)
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Obesity increases the risk of developing metabolic syndrome, diabetes, cardiovascular disease and associated comorbidities. Intermittent fasting (IF) and continuous calorie restriction (CCR) are fasting regimens known to reduce weight, which is at the heart of strategy in reducing obesity. IF and CCR restricts energy intake; however, CCR is harder to follow than IF. IF focuses more on time-restricted eating. This systematic review and meta-analysis examined the effectiveness of IF and CCR on body mass index (BMI), body weight, and metabolism in overweight and obese participants. This research showed that IF is significantly superior to CCR in weight loss in obese people. However, there was no difference in BMI between both regimens. There was a significant difference between IF and CCR for total cholesterol, triacylglycerol, and waist circumference. Further larger long-term robust studies are required to evaluate the effectiveness of different fasting regimens due to the high heterogeneity in this research. Healthcare professionals can use the results of this study to distinguish the weight loss effects between different fasting regimens.
Abstract
We conducted a systematic review and meta-analysis of randomized clinical trials and pilot trial studies to compare the effectiveness of intermittent fasting (IF) and continuous calorie restriction (CCR) in overweight and obese people. The parameters included body mass index (BMI), body weight, and other metabolism-related indicators. A systematic search in PubMed, Embase, Cochrane Library, and Web of Science was conducted up to January 2022. Standardized mean differences (SMDs) with 95% confidence intervals (CIs) were used to measure the effectiveness. Publication bias was assessed using Egger's test. The stability of the results was evaluated using sensitivity analyses. The significance of body weight change (SMD = -0.21, 95% CI (-0.40, -0.02) p = 0.028) was more significant after IF than CCR. There was no significant difference in BMI (SMD = 0.02, 95% CI (-0.16, 0.20) p = 0.848) between IF and CCR. These findings suggest that IF may be superior to CCR for weight loss in some respects.
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Comparison of the Effects of Intermittent Energy Restriction and Continuous Energy Restriction among Adults with Overweight or Obesity: An Overview of Systematic Reviews and Meta-Analyses.
Wang, J, Wang, F, Chen, H, Liu, L, Zhang, S, Luo, W, Wang, G, Hu, X
Nutrients. 2022;14(11)
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Obesity is the leading cause of cardiovascular disease, diabetes, hypertension, hyperlipidaemia, and some forms of cancer. 38% of people worldwide are overweight, and 20% are obese. To combat obesity and associated comorbidities, calorie restriction (CR) is found to be a cost-effective non-pharmacological intervention. Intermittent energy restriction (IER) and continuous energy restriction (CER) are two forms of CR characterised by notable calorie restriction and normal energy intake phases. Forms of IER included in this research are the 5:2 diet, alternate-day fasting (ADF), and time-restricted feeding (TRF). For weight loss, CER limits calorie intake by 15-40%. A total of eleven randomised controlled studies were included in this systematic review and meta-analysis to compare the effectiveness of IER protocols with CER in reducing weight, BMI and waist circumferences in overweight or obese individuals. Improvements in anthropometric parameters were not different between IER and CER. A long-term robust study is necessary to evaluate the effects of IER and CER on improving anthropometric and metabolic parameters due to the limitations and heterogeneity of current research evidence. Nevertheless, healthcare professionals can use the results of this study to understand the role of IER and CER in weight loss and their clinical relevance for improving overall health and lifespan.
Abstract
There is considerable heterogeneity across the evidence regarding the effects of intermittent energy restriction and continuous energy restriction among adults with overweight or obesity which presents difficulties for healthcare decision-makers and individuals. This overview of systematic reviews aimed to evaluate and synthesize the existing evidence regarding the comparison of the two interventions. We conducted a search strategy in eight databases from the databases' inception to December 2021. The quality of 12 systematic reviews was assessed with A Measurement Tool to Assess Systematic Reviews 2 (AMSTAR 2) and the Grading of Recommendations Assessment, Development and Evaluation (GRADE). One review was rated as high quality, 1 as moderate, 4 as low, and 6 as critically low. A meta-analysis of the original studies was conducted for comparison of primary intermittent energy restriction protocols with continuous energy restriction. Intermittent energy restriction did not seem to be more effective in weight loss compared with continuous energy restriction. The advantages of intermittent energy restriction in reducing BMI and waist circumference and improvement of body composition were not determined due to insufficient evidence. The evidence quality of systematic reviews and original trials remains to be improved in future studies.