Intermittent Fasting and Metabolic Health: From Religious Fast to Time‐Restricted Feeding

Abstract

Over the past 10 to 15 years, intermittent fasting has emerged as an unconventional approach to reduce body weight and improve metabolic health beyond simple calorie restriction. In this review, we summarize findings related to Ramadan and Sunnah fasting. We then discuss the role of caloric restriction not only as an intervention for weight control, but importantly, as a strategy for healthy aging and longevity. Finally, we review the four most common intermittent fasting (IF) strategies used to date for weight management and to improve cardiometabolic health. Weight loss is common after IF but does not appear to be different than daily caloric restriction when compared directly. IF may also provide additional cardiometabolic benefit, such as insulin sensitization, that is independent from weight loss. While no specific fasting regimen stands out as superior at this time, there is indeed heterogeneity in responses to these different IF diets. This suggests that one dietary regimen may not be ideally suited for every individual. Future studies should consider strategies for tailoring dietary prescriptions, including IF, based on advanced phenotyping and genotyping prior to diet initiation.

An exploratory investigation of the impact of ‘fast’ and ‘feed’ days during intermittent energy restriction on free-living energy balance behaviours and subjective states in women with overweight/obesity

“…Whether these differences in free-living appetite and eating behaviours between IER and CER contributed to the lower adherence and to the greater number of participants not achieving our per protocol criterion of ≥5% WL within 12 weeks is unclear. Therefore, these results should be confirmed in larger samples, and further research is required to phenotype individuals who successfully lose weight with IER strategies in order to personalise dietary prescriptions to improve WL, as recently highlighted by Hoddy et al [21].…”

“…A week-by-day interaction (p=0.005) revealed that feed day EI was greater at week 2 than final week (MΔ=295 [81, 509] kcal, p=0.004), but neither differed from baseline (p≥0.245). Free-living daily hunger (Figure 2B) did not differ between measures weeks (p=0.679), but was greater on fast days relative to feed days (MΔ=15[10,21] mm, p<0.001). A week-by-day interaction…”

Differential weight loss with intermittent fasting or daily calorie restriction in low‐ and high‐fitness phenotypes

“…With an increasing prevalence of obesity comes a heightened risk for the development of chronic health sequelae, including metabolic diseases, cardiovascular diseases, diabetes and cancer (Haslam & James, 2005;Withrow & Alter, 2011). Most weight-loss diet regimens, such as caloric restriction (CR), rely on limiting daily food intake, whereas time-restricted feeding and intermittent fasting (IF) limit the timing or duration of food availability (Hoddy et al, 2020). A common challenge with diet-induced weight loss is that the reduced weight is © 2021 The Authors.…”

Weight loss, hypertension and mental well-being improvements during COVID-19 with a multicomponent health promotion programme on Zoom: a service evaluation in primary care

“…A recent review of intermittent fasting protocols such as 5:2, alternate day fasting and time-restricted eating found that although weight loss can occur due to energy restriction, cardiometabolic health benefits such as increased insulin sensitivity can occur independent of weight loss. 17 Carbohydrate restriction has also been associated with reduced blood pressure in primary care patients. 11 15 Rather than hypertension being addressed by weight loss per se, it has been speculated that dietary changes may be responsible, 18 and there is evidence that hyperinsulinaemia increases sodium retention in people with T2D and hyperglycaemia.…”

“…A recent review of intermittent fasting protocols such as 5:2, alternate day fasting and time-restricted eating found that although weight loss can occur due to energy restriction, cardiometabolic health benefits such as increased insulin sensitivity can occur independent of weight loss. 17 …”