Comparative efficacy of energy-restricted dietary interventions in overweight and obese populations: A systematic review and network meta-analysis

This meta-analysis compared the effectiveness of different energy-restricted diets on body composition, glucose metabolism, and lipid metabolism in overweight and obese populations. Five databases were searched to identify relevant studies in English from inception until July 20, 2023, for randomized controlled trials of at least 2 weeks duration assessing the effects of continuous energy-restricted diets compared with any intermittent energy-restricted diet in obesity adults. The risk of bias was assessed using the Cochrane Risk of Bias Tool version 2.0, while the Grading of Recommendations, Assessment, Development, and Evaluations (GRADE) system was used to assess the certainty of the evidence. A non-informative prior distribution Bayesian network meta-analysis was conducted. Thirty-eight studies (3039 participants) assessing four energy-restricted diets were included. Three RCTs were at high risk of bias with a very low to moderate certainty of evidence. Combined with pairwise comparisons and surface under the cumulative ranking curve, alternate-day fasting may be the best energy restriction regimen with the potential to have the most beneficial effects on various aspects of the obesity population. More rigorously designed and long-term follow-up studies are warranted.

Dynamical alterations of brain function and gut microbiome in weight loss

Objective

Intermittent energy restriction (IER) is an effective weight loss strategy. However, little is known about the dynamic effects of IER on the brain-gut-microbiome axis.

Methods

In this study, a total of 25 obese individuals successfully lost weight after a 2-month IER intervention. FMRI was used to determine the activity of brain regions. Metagenomic sequencing was performed to identify differentially abundant gut microbes and pathways in from fecal samples.

Results

Our results showed that IER longitudinally reduced the activity of obese-related brain regions at different timepoints, including the inferior frontal orbital gyrus in the cognitive control circuit, the putamen in the emotion and learning circuit, and the anterior cingulate cortex in the sensory circuit. IER longitudinally reduced E. coli abundance across multiple timepoints while elevating the abundance of obesity-related Faecalibacterium prausnitzii, Parabacteroides distasonis, and Bacterokles uniformis. Correlation analysis revealed longitudinally correlations between gut bacteria abundance alterations and brain activity changes.

Conclusions

There was dynamical alteration of BGM axis (the communication of E. coli with specific brain regions) during the weight loss under the IER.

Metabolic impact of intermittent energy restriction and periodic fasting in patients with type 2 diabetes: a systematic review

CONTEXT

The effectiveness of intermittent energy restriction (IER) and periodic fasting (PF) in the management of type 2 diabetes (T2D) remains a subject of discussion.

OBJECTIVE

The aim of this systematic review is to summarize current knowledge of the effects of IER and PF in patients with T2D on markers of metabolic control and the need for glucose-lowering medication.

DATA SOURCES

PubMed, Embase, Emcare, Web of Science, Cochrane Library, CENTRAL, Academic Search Premier, Science Direct, Google Scholar, Wiley Online Library, and LWW Health Library were searched for eligible articles on March 20, 2018 (last update performed November 11, 2022). Studies that evaluated the effects of IER or PF diets in adult patients with T2D were included.

DATA EXTRACTION

This systematic review is reported according to PRISMA guidelines. Risk of bias was assessed through the Cochrane risk of bias tool. The search identified 692 unique records. Thirteen original studies were included.

DATA ANALYSIS

A qualitative synthesis of the results was constructed because the studies differed widely in terms of dietary interventions, study design, and study duration. Glycated hemoglobin (HbA1c) declined in response to IER or PF in 5 of 10 studies, and fasting glucose declined in 5 of 7 studies. In 4 studies, the dosage of glucose-lowering medication could be reduced during IER or PF. Two studies evaluated long-term effects (≥1 year after ending the intervention). The benefits to HbA1c or fasting glucose were generally not sustained over the long term. There are a limited number of studies on IER and PF interventions in patients with T2D. Most were judged to have at least some risk of bias.

CONCLUSION

The results of this systematic review suggest that IER and PF can improve glucose regulation in patients with T2D, at least in the short term. Moreover, these diets may allow for dosage reduction of glucose-lowering medication.

SYSTEMATIC REVIEW REGISTRATION

PROSPERO registration no. CRD42018104627.

Intermittent energy restriction changes the regional homogeneity of the obese human brain

Background

Intermittent energy restriction (IER) is an effective weight loss strategy. However, the accompanying changes in spontaneous neural activity are unclear, and the relationship among anthropometric measurements, biochemical indicators, and adipokines remains ambiguous.

Methods

Thirty-five obese adults were recruited and received a 2-month IER intervention. Data were collected from anthropometric measurements, blood samples, and resting-state functional magnetic resonance imaging at four time points. The regional homogeneity (ReHo) method was used to explore the effects of the IER intervention. The relationships between the ReHo values of altered brain regions and changes in anthropometric measurements, biochemical indicators, and adipokines (leptin and adiponectin) were analyzed.

Results

Results showed that IER significantly improved anthropometric measurements, biochemical indicators, and adipokine levels in the successful weight loss group. The IER intervention for weight loss was associated with a significant increase in ReHo in the bilateral lingual gyrus, left calcarine, and left postcentral gyrus and a significant decrease in the right middle temporal gyrus and right cerebellum (VIII). Follow-up analyses showed that the increase in ReHo values in the right LG had a significant positive correlation with a reduction in Three-factor Eating Questionnaire (TFEQ)-disinhibition and a significant negative correlation with an increase in TFEQ-cognitive control. Furthermore, the increase in ReHo values in the left calcarine had a significant positive correlation with the reduction in TFEQ-disinhibition. However, no significant difference in ReHo was observed in the failed weight loss group.

Conclusion

Our study provides objective evidence that the IER intervention reshaped the ReHo of some brain regions in obese individuals, accompanied with improved anthropometric measurements, biochemical indicators, and adipokines. These results illustrated that the IER intervention for weight loss may act by decreasing the motivational drive to eat, reducing reward responses to food cues, and repairing damaged food-related self-control processes. These findings enhance our understanding of the neurobiological basis of IER for weight loss in obesity.

continuous energy restriction on cardiometabolic risk factors in patients with metabolic syndrome: a meta-analysis and systematic review

Background

This is a systematic review and meta-analysis to compare the efficacy of intermittent energy restriction (IER) vs. continuous energy restriction (CER) on weight loss, body composition, blood pressure, and other cardiometabolic risk factors in patients with metabolic syndrome (MetS) risk factors.

Methods

We searched and screened PubMed, Embase, Cochrane Library, and Web of Science from inception to May 8, 2022 for randomized controlled trials. Two review authors independently selected studies, extracted data, assessed quality and risk of bias and cross-checked extracts to resolve discrepancies when required. We expressed effect size as mean difference (MD) and 95% confidence interval (CI). The major outcome was the improvement of MetS risk factors, including changes in waist circumference (WC), triglycerides (TG), high-density lipoprotein cholesterol (HDL-c), blood pressure (BP), and fasting plasma glucose (FPG) levels. The secondary outcomes were body weight (BW), body mass index (BMI), body fat (BF), fat free mass (FFM), hip circumference (HC), fasting insulin (FINs), total cholesterol (TC), and low-density lipoprotein cholesterol (LDL-c).

Results

The meta-analysis included 16 articles (20 trials) with a total of 1,511 participants. All studies had a low risk of bias for random sequence generation. The IER and CER intervention equally improved MetS risk factors WC (MD = -0.47, 95% CI [-1.19, 0.25]), TG (MD = -0.02 mmol/L, 95% CI [-0.11, 0.07]), FPG (MD = -0.02 mmol/L, 95% CI [-0.10, 0.05]) and BP (systolic blood pressure: MD = 0.93 mmHg, 95% CI [-2.74, 4.61]; diastolic blood pressure: MD =1.15 mmHg, 95% CI [-0.24, 2.55]), but HDL-c (MD = 0.03 mmol/L, 95% CI [0.01, 0.05]) was significant improved in IER when compared with CER. For second outcomes, BW (MD = -0.8 kg, 95% CI [-1.26, -0.33]), BF (MD = -0.75 kg, 95% CI [-1.73, -0.13]) and FFM (MD = -0.49 kg, 95% CI [-0.92, -0.05]) were also significant improved in IER, and not for other outcomes.

Conclusion

Both IER and CER could improve MetS biomarkers, but IER was more effective than CER in the improvement of HDL-c only. For secondary outcomes, IER was also more effective for BW, BF and FFM, but there were no differences in effects for other outcomes.

continuous energy restriction combined high-intensity interval training on overweight/obese adults: A randomized controlled trial

BACKGROUND

Intermittent energy restriction (IER) and continuous energy restriction (CER) are increasingly popular dietary approaches used for weight loss and overall health. These energy restriction protocols combined with exercise on weight loss and other health outcomes could achieve additional effects in a short-term intervention.

OBJECTIVES

To evaluate the effects of a 4-week IER or CER program on weight, blood lipids, and CRF in overweight/obese adults when combined with high-intensity interval training (HIIT).

METHODS

Forty-eight overweight/obese adults [age: 21.3 ± 2.24 years, body mass index (BMI): 25.86 ± 2.64 kg⋅m-2] were randomly assigned to iER, cER, and normal diet (ND) groups (n = 16 per group), each consisting of a 4-week intervention. All of the groups completed HIIT intervention (3 min at 80% of V̇O2max followed by 3 min at 50% of V̇O2max ), 30 min/training sessions, five sessions per week. iER subjects consumed 30% of energy needs on 2 non-consecutive days/week, and 100% of energy needs on another 5 days; cER subjects consumed 70% of energy needs; and ND subjects consumed 100% of energy needs. Body composition, waist circumference (WC) and hip circumference (HC), triglyceride (TG), total cholesterol (TC), low-density lipoprotein-cholesterol (LDL-c), high-density lipoprotein-cholesterol (HDL-c), and cardiorespiratory fitness (CRF) were measured before and after the intervention.

RESULTS

Of the total 57 participants who underwent randomization, 48 (84.2%) completed the 4-week intervention. After intervention body composition and body circumference decreased in three groups, but no significant differences between groups. The iER tends to be superior to cER in the reduction of body composition and body circumference. The mean body weight loss was 4.57 kg (95% confidence interval [CI], 4.1-5.0, p < 0.001) in iER and 2.46 kg (95% CI, 4.1-5.0, p < 0.001) in iER. The analyses of BMI, BF%, WC, and HC were consistent with the primary outcome results. In addition, TG, TC, HDL-c, and CRF improved after intervention but without significant changes (p > 0.05).

CONCLUSION

Both IER and CER could be effective in weight loss and increased CRF when combined with HIIT. However, iER showed greater benefits for body weight, BF%, WC, and HC compared with cER.

The Role of Intermittent Fasting in the Management of Nonalcoholic Fatty Liver Disease: A Narrative Review

Intermittent fasting is a non-pharmacological dietary approach to management of obesity and metabolic syndrome, involving periodic intervals of complete or near-complete abstinence from food and energy-containing fluids. This dietary strategy has recently gained significant popularity in mainstream culture and has been shown to induce weight loss in humans, reduce gut and systemic inflammation, and improve gut microbial diversity and dysbiosis (largely in animal models). It has been hypothesized that intermittent fasting could be beneficial in the management of nonalcoholic fatty liver disease, given the condition's association with obesity. This review summarizes protocols, potential mechanisms of action, and evidence for intermittent fasting in nonalcoholic fatty liver disease. It also highlights practical considerations for implementing intermittent fasting in clinical practice. A search of the literature for English-language articles related to intermittent fasting or time-restricted feeding and liver disease was completed in PubMed and Google Scholar. Potential mechanisms of action for effects of intermittent fasting included modulation of circadian rhythm, adipose tissue and adipokines, gut microbiome, and autophagy. Preclinical, epidemiological, and clinical trial data suggested clinical benefits of intermittent fasting on metabolic and inflammatory markers in humans. However, there was a paucity of evidence of its effects in patients with nonalcoholic fatty liver disease. More clinical studies are needed to determine mechanisms of action and to evaluate safety and efficacy of intermittent fasting in this population.

Effects of Intermittent Compared With Continuous Energy Restriction on Blood Pressure Control in Overweight and Obese Patients With Hypertension

Background and Aims: Weight-loss diets reduce body weight and improve blood pressure control in hypertensive patients. Intermittent energy restriction (IER) is an alternative to continuous energy restriction (CER) for weight reduction. We aimed to compare the effects of IER with those of CER on blood pressure control and weight loss in overweight and obese patients with hypertension during a 6-month period.

Methods: Two hundred and five overweight or obese participants (BMI 28.7 kg/m²) with hypertension were randomized to IER (5:2 diet, a very-low-calorie diet for 2 days per week, 500 kcal/day for women and 600 kcal/day for men, along with 5 days of a habitual diet) compared to a moderate CER diet (1,000 kcal/day for women and 1,200 kcal/day for men) for 6 months. The primary outcomes of this study were changes in blood pressure and weight, and the secondary outcomes were changes in body composition, glycosylated hemoglobin A1c (HbA1c), and blood lipids.

Results: Of the 205 randomized participants (118 women and 87 men; mean [SD] age, 50.2 [8.9] years; mean [SD] body mass index, 28.7 [2.6]; mean [SD] systolic blood pressure, 143 [10] mmHg; and mean [SD] diastolic blood pressure, 91 [9] mmHg), 173 completed the study. The intention-to-treat analysis demonstrated that IER and CER are equally effective for weight loss and blood pressure control: the mean (SEM) weight change with IER was −7.0 [0.6] kg vs. −6.8 [0.6] kg with CER, the mean (SEM) systolic blood pressure with IER was −7 [0.7] mmHg vs. −7 [0.6] mmHg with CER, and the mean (SEM) diastolic blood pressure with IER was −6 [0.5] mmHg vs. −5 [0.5] mmHg with CER, (diet by time P = 0.62, 0.39, and 0.41, respectively). There were favorable improvements in body composition, HbA1c, and blood lipid levels, with no differences between groups. Effects did not differ according to completer analysis. No severe hypoglycemia occurred in either group during the trial.

Conclusions: Intermittent energy restriction is an effective alternative diet strategy for weight loss and blood pressure control and is comparable to CER in overweight and obese patients with hypertension.

Clinical Trial Registration:http://www.chictr.org.cn, identifier: ChiCTR2000040468.

The Comparison of the Effects between Continuous and Intermittent Energy Restriction in Short-Term Bodyweight Loss for Sedentary Population: A Randomized, Double-Blind, Controlled Trial

Objective: To compare the effects of continuous energy restriction (CER) and intermittent energy restriction (IER) in bodyweight loss plan in sedentary individuals with normal bodyweight and explore the influence factors of effect and individual retention. Methods: 26 participants were recruited in this randomized controlled and double-blinded trial and allocated to CER and IER groups. Bodyweight (BW), body mass index (BMI), and resting metabolic rate (RMR) would be collected before and after a 4-week (28 days) plan which included energy restriction (CER or IER) and moderate-intensity exercise. Daily intake of three major nutrients (protein, carbohydrate, fat) and calories were recorded. Results: A significant decrease in BW and BMI were reported within each group. No statistically significant difference in the change of RMR in CERG. No statistically significant difference was reported in the effect between groups, neither as well the intake of total calories, three major nutrients, and individual plan retention. The influence factors of IER and CER are different. Conclusion: Both CER and IER are effective and safe energy restriction strategies in the short term. Daily energy intake and physical exercise are important to both IER and CER.

Weight Loss Barriers and Dietary Quality of Intermittent and Continuous Dieters in Women with a History of Gestational Diabetes

Weight-loss after gestational diabetes (GDM) lowers the risk of type-2 diabetes (T2DM). Intermittent energy restriction (IER) produces comparable weight-loss to continuous energy restriction (CER), but long-term adherence remains difficult in this population. This exploratory secondary analysis of a 12-month trial comparing IER to CER following GDM examined weight-loss and dietary quality associated with barriers to weight-loss or T2DM risk perception as assessed in a Likert scale questionnaire at baseline. The participants had a median (IQR) BMI of 32.6 (9.4) kg/m² and 3 (4) years postpartum (n = 121). Forty-five percent (n = 54) of the participants thought they were at a high risk of developing T2DM. Greater affordability of healthy food was related with greater weight-loss at 3 months (p = 0.044, n = 85). At 12 months, there was no significant relationship between weight-loss and the barriers to weight-loss (p > 0.05). CER had superior improvement in dietary quality at 12 months (CER 11 ± 10, IER 6 ± 5.6, n = 42, p = 0.05). Under the Theoretical Domains Framework, the barriers were predominantly related to behavioral regulation (n = 83, 69%; n = 76, 63%) and environmental context and resources (n = 67, 56%). Interventions for diabetes prevention in this population should include behavioral regulation strategies, consider the family home environment, and ensure that the risk of T2DM is conveyed. Women choosing IER may benefit from education to improve their dietary quality.

Novel dietary interventions for adolescents with obesity: A narrative review

Adolescent obesity is increasing and a range of treatment approaches are needed. Provision of tailored treatment options accounting for individual and family needs, preferences, and capacity may encourage adolescents with obesity to seek treatment, and/or improve treatment outcomes. Delivered by trained health care professionals, novel dietary interventions may have utility for adolescents not responding to conventional diets, adolescents with comorbidities or severe obesity, and/or when rapid or substantial weight loss is required. This review describes current evidence and clinical considerations relating to the use of very low energy diets, low carbohydrate diets, and intermittent energy restriction in the treatment of adolescent obesity. Emerging evidence on the use of these novel dietary interventions demonstrates short-term weight-related and cardiometabolic improvements. While the evidence is encouraging, and no serious adverse effects have been reported, monitoring of intervention safety is essential. Considerations for health care professionals providing care to adolescents include nutritional adequacy, psychosocial health and social relationships during the intervention. Furthermore, long-term weight-related, cardiometabolic and psychological health outcomes of these dietary interventions are not well understood. Large randomised controlled trials are warranted to inform clinical practice and future guidelines for the use of novel dietary interventions in adolescents with obesity.

The effect of intermittent energy restriction on weight loss and diabetes risk markers in women with a history of gestational diabetes: a 12-month randomized control trial

BACKGROUND

Weight loss after gestational diabetes (GDM) can prevent or delay the onset of type 2 diabetes. Intermittent energy restriction (IER) may offer an alternative to continuous energy restriction (CER) for weight loss.

OBJECTIVES

We compared the effects of IER (2 days per week) to daily CER over 12 mo on weight loss and diabetes risk markers in overweight women with previous GDM.

METHODS

Overweight females (n = 121) ≥18 y were randomized 1:1 to either IER [2-d 500 kcal (2100 kJ); n = 61] or CER [1500 kcal (6000 kJ); n = 60] in this 12-mo noninferiority trial.

RESULTS

The trial was completed by 62 participants with a median age of 39.6 y [Quartile (Q) 1 to Quartile 3, 34.9 to 43.9 y] with a median BMI of 32.6 kg/m2 (Q1 to Q3, 28.5 to 37.9 kg/m2) at a median of 2.9 y after GDM (Q1 to Q3, 2.1 to 6.4 y; 49% attrition; IER n = 29; CER n = 30; P = 0.8). The mean ± SD weight loss was significant over time (P < 0.001) but not by diet group (IER -4.8 ± 5.0 kg; CER -3.2 ± 5.0; P = 0.2). The mean between-group difference was -1.6 kg (95% CI: -4.2 to 1.0 kg; P = 0.2). There were no significant between-group differences in change in HbA1c, fasting plasma glucose, fasting serum insulin, HOMA-IR or 2-h oral glucose tolerance at 12 mo (p>0.05). The trial was registered at https://www.anzctr.org.au/ (ACTRN12617001476325).

CONCLUSIONS

IER produces comparable weight loss to CER over 12 mo in overweight women with previous GDM. The high dropout rate in this study is a limitation in the interpretation of these results. Larger studies are needed to confirm noninferiority of IER compared to CER.

Intermittent Energy Restriction, Weight Loss and Cardiometabolic Risk: A Critical Appraisal of Evidence in Humans

Dietary patterns with intermittent energy restriction (IER) have been proposed as an attractive alternative to continuous energy restriction (CER) for the management of obesity and its associated comorbidities. The most widely studied regimens of IER comprise energy restriction on two days per week (5:2), alternate-day energy restriction by 60-70% (ADF), and timely restriction of energy intake during a specific time window within the day (TRF; time-restricted feeding). Although there is some evidence to suggest that IER can exert beneficial effects on human cardiometabolic health, yet is apparently not superior compared to CER, there are still some critical issues/questions that warrant further investigation: (i) high-quality robust scientific evidence regarding the long-term effects of IER (safety, efficacy, compliance) is limited since the vast majority of intervention studies had a duration of less than 6 months; (ii) whether the positive effects of IER are independent of or actually mediated by weight loss remains elusive; (iii) it remains unknown whether IER protocols are a safe recommendation for the general population; (iv) data concerning the impact of IER on ectopic fat stores, fat-free mass, insulin resistance and metabolic flexibility are inconclusive; (v) the cost-effectiveness of IER dietary regimens has not been adequately addressed; (vi) direct head-to-head studies comparing different IER patterns with variable macronutrient composition in terms of safety and efficacy are scarce; and (vii) evidence is limited with regard to the efficacy of IER in specific populations, including males, the elderly and patients with morbid obesity and diabetes mellitus. Until more solid evidence is available, individualization and critical perspective are definitely warranted to determine which patients might benefit the most from an IER intervention, depending on their personality traits and most importantly comorbid health conditions.

Adherence and Dietary Composition during Intermittent vs. Continuous Calorie Restriction: Follow-Up Data from a Randomized Controlled Trial in Adults with Overweight or Obesity

Although intermittent calorie restriction (ICR) has become popular as an alternative weight loss strategy to continuous calorie restriction (CCR), there is insufficient evidence on diet quality during ICR and on its feasibility over longer time periods. Thus, we compared dietary composition and adherence between ICR and CCR in a follow-up analysis of a randomized trial. A total of 98 participants with overweight or obesity [BMI (kg/m²) 25-39.9, 35-65 years, 49% females] were randomly assigned to ICR, operationalized as a "5:2 diet" (energy intake: ~100% on five non-restricted (NR) days, ~25% on two restricted (R) days), or CCR (daily energy intake: ~80%). The trial included a 12-week (wk) intervention phase, and follow-up assessments at wk24, wk50 and wk102. Apart from a higher proportion of energy intake from protein with ICR vs. CCR during the intervention (wk2: p < 0.001; wk12: p = 0.002), there were no significant differences with respect to changes in dietary composition over time between the groups, while overall adherence to the interventions appeared to be good. No significant difference between ICR and CCR regarding weight change at wk102 was observed (p = 0.63). However, self-reported adherence was worse for ICR than CCR, with 71.1% vs. 32.5% of the participants reporting not to or only rarely have followed the regimen to which they were assigned between wk50 and wk102. These results indicate that within a weight management setting, ICR and CCR were equivalent in achieving modest weight loss over two years while affecting dietary composition in a comparable manner.

Intermittent and continuous energy restriction result in similar weight loss, weight loss maintenance, and body composition changes in a 6 month randomized pilot study

Poor adherence is a barrier to successful weight control. Intermittent energy restriction (IER) provides an alternative approach to those for whom daily energy restriction is not ideal. This study assessed changes in weight, body composition, and macronutrient intake for an IER and a continuous energy restriction (CONT) approach within a multicomponent weight management intervention. We randomized 35 adults with overweight/obesity (BMI = 31.2 ± 2.4 kg/m² ) to CONT or IER for 24 weeks (12-week weight loss intervention and 12 weeks of weight loss maintenance). Diets were delivered within a multimodal weight management program including weekly group meetings with a registered dietitian, increased physical activity, and a comprehensive lifestyle change program. Retention and adherence were similar for CONT and IER. Weight, BMI, fat mass, percentage body fat, waist circumference, hip circumference, blood pressure, and heart rate all decreased after 24 weeks (all, P < .01), but there were no main effects of group (all, P > .27). Weight loss was clinically relevant in both CONT (11.38 ± 7.9%) and IER (9.37 ± 9.7%), and the proportion of each group achieving 5% weight loss was 82 and 61% (P = .16), respectively. Participant satisfaction was high in both groups. The results from this study (a) support the feasibility of IER as an alternative for weight loss and weight loss maintenance, (b) indicate that IER is an effective alternative to CONT for weight control and improvements in body composition, and (c) emphasize the importance of intensive lifestyle interventions with ongoing support for effective behaviour modification.

Intermittent Versus Continuous Low-Energy Diet in Patients With Type 2 Diabetes: Protocol for a Pilot Randomized Controlled Trial

BACKGROUND

Intensive face-to-face weight loss programs using continuous low-energy diets (CLEDs) providing approximately 800 kcal per day (3347 kJ per day) can produce significant weight loss and remission from type 2 diabetes (T2D). Intermittent low-energy diets (ILEDs) and remotely delivered programs could be viable alternatives that may support patient choice and adherence.

OBJECTIVE

This paper describes the protocol of a pilot randomized controlled trial to test the feasibility and potential efficacy of remotely supported isocaloric ILED and CLED programs among patients with overweight and obesity and T2D.

METHODS

A total of 79 participants were recruited from primary care, two National Health Service hospital trusts, and a voluntary T2D research register in the United Kingdom. The participants were randomized to a remotely delivered ILED (n=39) or CLED (n=40). The active weight loss phase of CLED involved 8 weeks of Optifast 820 kcal/3430 kJ formula diet, followed by 4 weeks of food reintroduction. The active weight loss phase of ILED (n=39) comprised 2 days of Optifast 820 kcal/3430 kJ diet and 5 days of a portion-controlled Mediterranean diet for 28 weeks. Both groups were asked to complete 56 Optifast 820 kcal/3430 kJ days during their active weight loss phase with an equivalent energy deficit. The diets were isocaloric for the remainder of the 12 months. CLED participants were asked to follow a portion-controlled Mediterranean diet 7 days per week. ILED followed 1-2 days per week of a food-based 820 kcal/3430 kJ diet and a portion-controlled Mediterranean diet for 5-6 days per week. Participants received high-frequency (weekly, fortnightly, or monthly depending on the stage of the trial) multidisciplinary remote support from a dietitian, nurse, exercise specialist, and psychologist via telephone or the Oviva smartphone app. The primary outcomes of the study were uptake, weight loss, and changes in glycated hemoglobin at 12 months. An outcome assessment of trial retention was retrospectively added. Secondary outcomes included an assessment of adherence and adverse events. A qualitative evaluation was undertaken via interviews with participants and health care professionals who delivered the intervention.

RESULTS

A total of 79 overweight or obese participants aged 18-75 years and diagnosed with T2D in the last 8 years were recruited to the Manchester Intermittent and Daily Diet Diabetes App Study (MIDDAS). Recruitment began in February 2018, and data collection was completed in February 2020. Data analysis began in June 2020, and the first results are expected to be submitted for publication in 2021.

CONCLUSIONS

The outcomes of the MIDDAS study will inform the feasibility of remotely delivered ILED and CLED programs in clinical practice and the requirement for a larger-scale randomized controlled trial.

TRIAL REGISTRATION

International Standard Randomized Controlled Trial Number (ISRCTN) 15394285; http://www.isrctn.com/ISRCTN15394285.

INTERNATIONAL REGISTERED REPORT IDENTIFIER (IRRID)

DERR1-10.2196/21116.

Women's Barriers to Weight Loss, Perception of Future Diabetes Risk and Opinions of Diet Strategies Following Gestational Diabetes: An Online Survey

Weight loss after gestational diabetes (GDM) reduces the risk of type 2 diabetes (T2DM); however, weight loss remains challenging in this population. In order to explore perceptions of T2DM risk, barriers to weight loss, and views of diet strategies in women with previous GDM, a cross-sectional online survey of n = 429 women in Australia aged ≥18 years with previous GDM was conducted. Opinions of intermittent energy restriction (IER) were of interest. Seventy-five percent of responders (n = 322) had overweight or obesity, and 34% (n = 144) believed they had a high risk of developing T2DM. Within the Theoretical Domains Framework, barriers to weight loss were prominently related to Environmental Context and Resources, Beliefs about Capabilities, and Behavioural Regulation. Exercising was the most tried method of weight loss over other diet strategies (71%, n = 234) and weight loss support by a dietician was appealing as individual appointments (65%, n = 242) or an online program (54%, n = 200). Most women (73%, n = 284) had heard of IER (the "5:2 diet"), but only 12% (n = 34) had tried it. Open comments (n = 100) revealed mixed views of IER. Women in Australia with previous GDM were found to lack a self-perceived high risk of developing T2DM and expressed barriers to weight loss related to their family environment, beliefs about their capabilities and behavioural regulation. IER is appealing for some women with previous GDM; however, views vary.

Impact of intermittent energy restriction on anthropometric outcomes and intermediate disease markers in patients with overweight and obesity: systematic review and meta-analyses

This systematic review aims to investigate the effects of intermittent energy restriction (IER) on anthropometric outcomes and intermediate disease markers. A systematic literature search was conducted in three electronic databases. Randomized controlled trials (RCTs) were included if the intervention lasted ≥12 weeks and IER was compared with either continuous energy restriction (CER) or a usual diet. Random-effects meta-analysis was performed for eight outcomes. Certainty of evidence was assessed using GRADE. Seventeen RCTs with 1328 participants were included. IER in comparison to a usual diet may reduce body weight (mean difference [MD]: -4.83 kg, 95%-CI: -5.46, -4.21; n = 6 RCTs), waist circumference (MD: -1.73 cm, 95%-CI: -3.69, 0.24; n = 2), fat mass (MD: -2.54 kg, 95%-CI: -3.78, -1.31; n = 6), triacylglycerols (MD: -0.20 mmol/L, 95%-CI: -0.38, -0.03; n = 5) and systolic blood pressure (MD: -6.11 mmHg, 95%-CI: -9.59, -2.64; n = 5). No effects were observed for LDL-cholesterol, fasting glucose, and glycosylated-hemoglobin. Both, IER and CER have similar effect on body weight (MD: -0.55 kg, 95%-CI: -1.01, -0.09; n = 13), and fat mass (MD: -0.66 kg, 95%-CI: -1.14, -0.19; n = 10), and all other outcomes. In conclusion, IER improves anthropometric outcomes and intermediate disease markers when compared to a usual diet. The effects of IER on weight loss are similar to weight loss achieved by CER.

Matched Weight Loss Through Intermittent or Continuous Energy Restriction Does Not Lead To Compensatory Increases in Appetite and Eating Behavior in a Randomized Controlled Trial in Women with Overweight and Obesity

BACKGROUND

Continuous energy restriction (CER) is purported to be problematic because of reductions in fat-free mass (FFM), compensatory motivation to overeat, and weakened satiety. Intermittent energy restriction (IER) is an alternative behavioral weight loss (WL) strategy that may mitigate some of these limitations.

OBJECTIVE

The objective of the DIVA study was to compare the effects of CER and IER on appetite when the degree of WL (≥5%) is matched.

METHODS

Women with overweight/obesity (BMI 25.0-34.9 kg/m2; age 18-55 y) were recruited for this controlled-feeding RCT via CER (25% daily energy restriction) or IER (alternating ad libitum and 75% energy restriction days). Probe days were conducted at baseline and post-intervention to assess body composition, ad libitum energy intake and subjective appetite in response to a fixed-energy breakfast, and eating behavior traits. After baseline measurements, participants were allocated to CER (n = 22) or IER (n = 24). Per protocol analyses (≥5% WL within 12 wk) were conducted with use of repeated measures ANOVA.

RESULTS

Thirty of 37 completers reached ≥5% WL [CER (n = 18): 6.3 ± 0.8% in 57 ± 16 d, IER (n = 12): 6.6 ± 1.1% in 67 ± 13 d; % WL P = 0.43 and days P = 0.10]. Fat mass [-3.9 (95% CI: -4.3, -3.4) kg] and FFM [-1.3 (95% CI: -1.6, -1.0) kg] were reduced post-WL (P < 0.001), with no group differences. Self-selected meal size decreased post-WL in CER (P = 0.03) but not in IER (P = 0.19). Hunger AUC decreased post-WL (P < 0.05), with no group differences. Satiety quotient remained unchanged and was similar in both groups. Both interventions improved dietary restraint, craving control, susceptibility to hunger, and binge eating (P < 0.001).

CONCLUSIONS

Controlled ≥5% WL via CER or IER did not differentially affect changes in body composition, reductions in hunger, and improvements in eating behavior traits. This suggests that neither CER nor IER lead to compensatory adaptations in appetite in women with overweight/obesity. This trial was registered at clinicaltrials.gov as NCT03447600.

Intermittent fasting, Paleolithic, or Mediterranean diets in the real world: exploratory secondary analyses of a weight-loss trial that included choice of diet and exercise

BACKGROUND

Intermittent fasting (IF) and Paleolithic (Paleo) diets produce weight loss in controlled trials, but minimal evidence exists regarding long-term efficacy under free-living conditions without intense dietetic support.

OBJECTIVES

This exploratory, observational analysis examined adherence, dietary intake, weight loss, and metabolic outcomes in overweight adults who could choose to follow Mediterranean, IF, or Paleo diets, and standard exercise or high-intensity interval training (HIIT) programs, as part of a 12-mo randomized controlled trial investigating how different monitoring strategies influenced weight loss (control, daily self-weighing, hunger training, diet/exercise app, brief support).

METHODS

A total of 250 overweight [BMI (in kg/m2) ≥27] healthy adults attended an individualized dietary education session (30 min) relevant to their self-selected diet. Dietary intake (3-d weighed diet records), weight, body composition, blood pressure, physical activity (0, 6, and 12 mo), and blood indexes (0 and 12 mo) were assessed. Mean (95% CI) changes from baseline were estimated using regression models. No correction was made for multiple tests.

RESULTS

Although 54.4% chose IF, 27.2% Mediterranean, and 18.4% Paleo diets originally, only 54% (IF), 57% (Mediterranean), and 35% (Paleo) participants were still following their chosen diet at 12 mo (self-reported). At 12 mo, weight loss was -4.0 kg (95% CI: -5.1, -2.8 kg) in IF, -2.8 kg (-4.4, -1.2 kg) in Mediterranean, and -1.8 kg (-4.0, 0.5 kg) in Paleo participants. Sensitivity analyses showed that, due to substantial dropout, these may be overestimated by ≤1.2 kg, whereas diet adherence increased mean weight loss by 1.1, 1.8, and 0.3 kg, respectively. Reduced systolic blood pressure was observed with IF (-4.9 mm Hg;  -7.2, -2.6 mm Hg) and Mediterranean (-5.9 mm Hg; -9.0, -2.7 mm Hg) diets, and reduced glycated hemoglobin with the Mediterranean diet (-0.8 mmol/mol; -1.2, -0.4 mmol/mol). However, the between-group differences in most outcomes were not significant and these comparisons may be confounded due to the nonrandomized design.

CONCLUSIONS

Small differences in metabolic outcomes were apparent in participants following self-selected diets without intensive ongoing dietary support, even though dietary adherence declined rapidly. However, results should be interpreted with caution given the exploratory nature of analyses. This trial was registered with the Australian New Zealand Clinical Trials Registry as ACTRN12615000010594 at https://www.anzctr.org.au.

Effects of Weight Loss on FGF-21 in Human Subjects: An Exploratory Study

Fibroblast growth factor-21 (FGF-21), is a protein involved in cell growth and differentiation, development, wound repair and metabolism. Research looking at the impact of weight loss on FGF-21 levels is limited. The objective of this exploratory study was to determine changes in serum FGF-21 levels following weight loss induced by either continuous energy restriction or intermittent energy restriction. A sub cohort of participants who completed a 12-month dietary intervention trial following continuous energy restriction, or a week-on week-off energy restriction pattern, were selected for analysis. FGF-21 levels were not altered by weight loss and were not correlated with body weight or BMI at baseline or 12 months. Weight loss after 12 months either through continuous energy restriction or intermittent energy restriction was −5.9 ± 4.5 and −4.9 ± 3.4 kg, respectively. There was no change in FGF-21 levels, 0.3 ± 0.9 and 0.04 ± 0.2 ng/mL (p = 0.2). In conclusion, weight loss in healthy overweight or obesity subjects did not affect FGF-21 levels.

Time-restricted feeding plus resistance training in active females: a randomized trial

BACKGROUND

A very limited amount of research has examined intermittent fasting (IF) programs, such as time-restricted feeding (TRF), in active populations.

OBJECTIVE

Our objective was to examine the effects of TRF, with or without β-hydroxy β-methylbutyrate (HMB) supplementation, during resistance training (RT).

METHODS

This study employed a randomized, placebo-controlled, reduced factorial design and was double-blind with respect to supplementation in TRF groups. Resistance-trained females were randomly assigned to a control diet (CD), TRF, or TRF plus 3 g/d HMB (TRFHMB). TRF groups consumed all calories between 1200 h and 2000 h, whereas the CD group ate regularly from breakfast until the end of the day. All groups completed 8 wk of supervised RT and consumed supplemental whey protein. Body composition, muscular performance, dietary intake, physical activity, and physiological variables were assessed. Data were analyzed prior to unblinding using mixed models and both intention-to-treat (ITT) and per protocol (PP) frameworks.

RESULTS

Forty participants were included in ITT, and 24 were included in PP. Energy and protein intake (1.6 g/kg/d) did not differ between groups despite different feeding durations (TRF and TRFHMB: ∼7.5 h/d; CD: ∼13 h/d). Comparable fat-free mass (FFM) accretion (+2% to 3% relative to baseline) and skeletal muscle hypertrophy occurred in all groups. Differential effects on fat mass (CD: +2%; TRF: -2% to -4%; TRFHMB: -4% to -7%) were statistically significant in the PP analysis, but not ITT. Muscular performance improved without differences between groups. No changes in physiological variables occurred in any group, and minimal side effects were reported.

CONCLUSIONS

IF, in the form of TRF, did not attenuate RT adaptations in resistance-trained females. Similar FFM accretion, skeletal muscle hypertrophy, and muscular performance improvements can be achieved with dramatically different feeding programs that contain similar energy and protein content during RT. Supplemental HMB during fasting periods of TRF did not definitively improve outcomes. This study was prospectively registered at clinicaltrials.gov as NCT03404271.

Effects of Intermittent Energy Restriction Combined with a Mediterranean Diet on Reducing Visceral Adiposity: A Randomized Active Comparator Pilot Study

Intermittent energy restriction combined with a Mediterranean diet (IER+MED) has shown promise to reduce body fat and insulin resistance. In the Multiethnic Cohort Adiposity Phenotype Study, Japanese Americans had the highest visceral adipose tissue (VAT) when adjusting for total adiposity. We conducted this pilot study to demonstrate feasibility and explore efficacy of following IER+MED for 12 weeks to reduce VAT among East Asians in Hawaii. Sixty volunteers (aged 35-55, BMI 25-40 kg/m2, VAT ≥ 90 cm2 for men and ≥ 80 cm2 for women) were randomized to IER+MED (two consecutive days with 70% energy restriction and 5 days euenergetic MED) or an active comparator (euenergetic Dietary Approaches to Stop Hypertension (DASH) diet). Participants and clinic staff (except dietitians) were blinded to group assignments. IER+MED had significantly larger reductions in DXA-measured VAT and total fat mass (-22.6 ± 3.6 cm2 and -3.3 ± 0.4 kg, respectively) vs. DASH (-10.7 ± 3.5 cm2 and -1.6 ± 0.4 kg) (p = 0.02 and p = 0.005). However, after adjusting for total fat mass, change in VAT was not statistically different between groups; whereas, improvement in alanine transaminase remained significantly greater for IER+MED vs. DASH (-16.2 ± 3.8 U/L vs. -4.0 ± 3.6 U/L, respectively, p = 0.02). Attrition rate was 10%, and participants adhered well to study prescriptions with no reported major adverse effect. Results demonstrate IER+MED is acceptable, lowers visceral and total adiposity among East Asian Americans, and may improve liver function more effectively than a healthful diet pattern. ClinicalTrials.gov Identifier: NCT03639350.

Clinical Management of Intermittent Fasting in Patients with Diabetes Mellitus

Intermittent fasting is increasing in popularity as a means of losing weight and controlling chronic illness. Patients with diabetes mellitus, both types 1 and 2, comprise about 10% of the population in the United States and would likely be attracted to follow one of the many methods of intermittent fasting. Studies on the safety and benefits of intermittent fasting with diabetes are very limited though, and health recommendations unfortunately today arise primarily from weight loss gurus and animal studies. Medical guidelines on how to manage therapeutic intermittent fasting in patients with diabetes are non-existent. The evidence to build such a clinical guideline for people with a diabetes diagnosis is almost non-existent, with just one randomized trial and several case reports. This article provides an overview of the available knowledge and a review of the very limited pertinent literature on the effects of intermittent fasting among people with diabetes. It also evaluates the known safety and efficacy issues surrounding treatments for diabetes in the fasting state. Based on those limited data and a knowledge of best practices, this paper proposes expert-based guidelines on how to manage a patient with either type 1 or 2 diabetes who is interested in intermittent fasting. The safety of each relevant pharmaceutical treatment during a fasting period is considered. When done under the supervision of the patient’s healthcare provider, and with appropriate personal glucose monitoring, intermittent fasting can be safely undertaken in patients with diabetes.

Pilot Study of Novel Intermittent Fasting Effects on Metabolomic and Trimethylamine N-oxide Changes During 24-hour Water-Only Fasting in the FEELGOOD Trial

Intermittent fasting (IF) has been connected with health benefits such as weight loss, lower risk of coronary artery disease (CAD) and diabetes, increased longevity, and improved quality of life. However, the mechanisms of these IF benefits in humans require further investigation. This study sought to elucidate some of these mechanisms through secondary analyses of the Fasting and ExprEssion of Longevity Genes during fOOD abstinence (FEELGOOD) trial, in which apparently healthy participants were randomized in a Latin square design to a 24-h water-only fast and a 24-h ad libitum fed day. Two pathways were investigated, with trimethylamine N-oxide (TMAO) levels measured due to their association with elevated risk of CAD, along with conductance of a broad panel of metabolic analytes. Measurements were made at baseline, at the end of the fasting day, and at the end of the fed day. A fasting mean of 14.3 ng in TMAO was found versus the baseline mean of 27.1 ng with p = 0.019, although TMAO levels returned to baseline on refeeding. Further, acute alterations in levels of proline, tyrosine, galactitol, and urea plasma levels were observed along with changes in 24 other metabolites during the fasting period. These acute changes reveal short-term mechanisms which, with consistent repeated episodes of IF, may lead to improved health and reduced risk of CAD and diabetes.

Intermittent Dieting: Theoretical Considerations for the Athlete

Athletes utilise numerous strategies to reduce body weight or body fat prior to competition. The traditional approach requires continuous energy restriction (CER) for the entire weight loss phase (typically days to weeks). However, there is some suggestion that intermittent energy restriction (IER), which involves alternating periods of energy restriction with periods of greater energy intake (referred to as ‘refeeds’ or ‘diet breaks’) may result in superior weight loss outcomes than CER. This may be due to refeed periods causing transitory restoration of energy balance. Some studies indicate that intermittent periods of energy balance during energy restriction attenuate some of the adaptive responses that resist the continuation of weight and fat loss. While IER—like CER—is known to effectively reduce body fat in non-athletes, evidence for effectiveness of IER in athletic populations is lacking. This review provides theoretical considerations for successful body composition adjustment using IER, with discussion of how the limited existing evidence can be cautiously applied in athlete practice.

Rationale for novel intermittent dieting strategies to attenuate adaptive responses to energy restriction

Eating patterns involving intermittent energy restriction (IER) include 'intermittent fasting' where energy intake is severely restricted for several 'fasting' days per week, with 'refeeding' days (involving greater energy intake than during fasting days) at other times. Intermittent fasting does not improve weight loss compared to continuous energy restriction (CER), where energy intake is restricted every day. We hypothesize that weight loss from IER could be improved if refeeding phases involved restoration of energy balance (i.e. not ongoing energy restriction, as during intermittent fasting). There is some evidence in adults with overweight or obesity showing that maintenance of a lower weight may attenuate (completely or partially) some of the adaptive responses to energy restriction that oppose ongoing weight loss. Other studies show some adaptive responses persist unabated for years after weight loss. Only five randomized controlled trials in adults with overweight or obesity have compared CER with IER interventions that achieved energy balance (or absence of energy restriction) during refeeding phases. Two reported greater weight loss than CER, whereas three reported similar weight loss between interventions. While inconclusive, it is possible that achieving energy balance (i.e. avoiding energy restriction or energy excess) during refeeding phases may be important in realizing the potential of IER.

Effect of Intermittent Energy Restriction on Flow Mediated Dilatation, a Measure of Endothelial Function: A Short Report

Intermittent energy restriction is a popular alternative to daily energy restriction for weight loss; however, it is unknown if endothelial function, a risk factor for cardiovascular disease, is altered by periods of severe energy restriction. The objective of the study was to determine the impact of two consecutive very low energy intake days, which is the core component of the 5:2 intermittent energy restriction diet strategy, on endothelial function compared to consecutive ad libitum eating days. The secondary objective was to explore the effects of these dietary conditions on fasting glucose concentrations. This was a 4-week randomized, single-blinded, crossover study of 35 participants. Participants consumed a very low energy diet (500 calories for women, 600 calories for men) on two consecutive days per week and 5 days of habitual eating. In weeks 3 and 4 of the trial, participants had measurements of flow mediated dilatation (FMD) and blood samples taken following either 2 habitual eating days or 2 energy restricted days in a randomized order. FMD values were not different after the two eating states (8.6% vs. 8.3%, p = 0.7). All other outcome variables were unchanged. Endothelial function, as measured by flow mediated dilatation, was not altered by two consecutive very low energy intake days. Further investigations assessing the impact in specific population groups as well as different testing conditions would be beneficial.

Short-term intermittent energy restriction interventions for weight management: a systematic review and meta-analysis

This systematic review synthesized the available evidence on the effect of short-term periods of intermittent energy restriction (weekly intermittent energy restriction; ≥7-d energy restriction) in comparison with usual care (daily continuous energy restriction), in the treatment of overweight and obesity in adults. Six electronic databases were searched from inception to October 2016. Only randomized controlled trials of interventions (≥12 weeks) in adults with overweight and obesity were included. Five studies were included in this review. Weekly intermittent energy restriction periods ranged from an energy intake between 1757 and 6276 kJ/d^-1 . The mean duration of the interventions was 26 (range 14 to 48) weeks. Meta-analysis demonstrated no significant difference in weight loss between weekly intermittent energy restriction and continuous energy restriction post-intervention (weighted mean difference: -1.36 [-3.23, 0.51], p = 0.15) and at follow-up (weighted mean difference: -0.82 [-3.76, 2.11], p = 0.58). Both interventions achieved comparable weight loss of >5 kg and therefore were associated with clinical benefits to health. The findings support the use of weekly intermittent energy restriction as an alternative option for the treatment of obesity. Currently, there is insufficient evidence to support the long-term sustainable effects of weekly intermittent energy restriction on weight management.

Potential Benefits and Harms of Intermittent Energy Restriction and Intermittent Fasting Amongst Obese, Overweight and Normal Weight Subjects-A Narrative Review of Human and Animal Evidence

Intermittent energy restriction (IER) has become popular as a means of weight control amongst people who are overweight and obese, and is also undertaken by normal weight people hoping spells of marked energy restriction will optimise their health. This review summarises randomised comparisons of intermittent and isoenergetic continuous energy restriction for weight loss to manage overweight and obesity. It also summarises the potential beneficial or adverse effects of IER on body composition, adipose stores and metabolic effects from human studies, including studies amongst normal weight subjects and relevant animal experimentation. Six small short term (<6 month) studies amongst overweight or obese individuals indicate that intermittent energy restriction is equal to continuous restriction for weight loss, with one study reporting greater reductions in body fat, and two studies reporting greater reductions in HOMA insulin resistance in response to IER, with no obvious evidence of harm. Studies amongst normal weight subjects and different animal models highlight the potential beneficial and adverse effects of intermittent compared to continuous energy restriction on ectopic and visceral fat stores, adipocyte size, insulin resistance, and metabolic flexibility. The longer term benefits or harms of IER amongst people who are overweight or obese, and particularly amongst normal weight subjects, is not known and is a priority for further investigation.

Could Intermittent Energy Restriction and Intermittent Fasting Reduce Rates of Cancer in Obese, Overweight, and Normal-Weight Subjects? A Summary of Evidence

Animal studies and human observational data link energy restriction (ER) to reduced rates of carcinogenesis. Most of these studies have involved continuous energy restriction (CER), but there is increasing public and scientific interest in the potential health and anticancer effects of intermittent energy restriction (IER) or intermittent fasting (IF), which comprise periods of marked ER or total fasting interspersed with periods of normal eating. This review summarizes animal studies that assessed tumor rates with IER and IF compared with CER or ad libitum feed consumption. The relevance of these animal data to human cancer is also considered by summarizing available human studies of the effects of IER or IF compared with CER on cancer biomarkers in obese, overweight, and normal-weight subjects. IER regimens that include periods of ER alternating with ad libitum feed consumption for 1, 2, or 3 wk have been reported to be superior to CER in reducing tumor rates in most spontaneous mice tumor models. Limited human data from short-term studies (≤6 mo) in overweight and obese subjects have shown that IER can lead to greater improvements in insulin sensitivity (homeostasis model assessment) than can CER, with comparable reductions in adipokines and inflammatory markers and minor changes in the insulin-like growth factor axis. There are currently no data comparing IER or IF with CER in normal-weight subjects. The benefits of IER in these short-term trials are of interest, but not sufficient evidence to recommend the use of IER above CER. Longer-term human studies of adherence to and efficacy and safety of IER are required in obese and overweight subjects, as well as normal-weight subjects.

Weight-Loss Outcomes: A Systematic Review and Meta-Analysis of Intermittent Energy Restriction Trials Lasting a Minimum of 6 Months. Nutrients. 2016;8:E354. [PMID: 27338458 PMCID: PMC4924195 DOI: 10.3390/nu8060354]

The aim of this systematic review and meta-analysis is to summarise the effects of intermittent energy restriction on weight and biological markers in long term intervention studies of >6 months duration. An electronic search was performed using the MEDLINE, EMBASE and the Cochrane Library databases for intervention trials lasting 6 months or longer investigating the effects of intermittent energy restriction. A total of nine studies were identified as meeting the pre-specified criteria. All studies included an intermittent energy restriction arm, with six being directly compared to continuous energy restriction. A total of 981 subjects were enrolled and randomised, with weight loss observed in all intermittent energy restriction arms regardless of study duration or follow up length. Eight interventions in six trials were used for the meta-analyses, with results indicating neither intermittent or continuous energy restriction being superior with respect to weight loss, 0.084 ± 0.114 (overall mean difference between groups ± standard error; p = 0.458). The effects of intermittent energy restriction in the long term remain unclear. The number of long term studies conducted is very limited, and participant numbers typically small (less than 50 completers), indicating the need for larger, long term trials of 12 months or more, to be conducted in order to understand the impact of intermittent energy restriction on weight loss and long term weight management. Blood lipid concentrations, glucose, and insulin were not altered by intermittent energy expenditure in values greater than those seen with continuous energy restriction.