INTERMITTENT FASTING AND HUMAN METABOLIC HEALTH
J Acad Nutr Diet. 2015 Aug; 115(8): 1203–1212.
Published online 2015 Apr 6.
doi: 10.1016/j.jand.2015.02.018
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4516560/CONCLUSIONS
It is well known that in humans, even a single fasting interval (e.g., overnight) can reduce basal concentrations of metabolic biomarkers associated with chronic disease such as insulin and glucose. For example, patients are required to fast for 8–12 hours before blood draws to achieve steady-state fasting levels for many metabolic substrates. Therefore the important clinical and scientific question is whether adoption of a regular intermittent fasting regimen is a feasible and sustainable population-based strategy for promoting metabolic health. In addition, research is needed to test whether these regimens can complement or replace energy restriction and if so, whether they support long-term weight management. Below, we briefly summarize the major conclusions that can be drawn based on the current evidence.
Studies in rodents and other nocturnal mammals support the hypothesis that intermittent fasting and restricting the availability of chow to the normal nighttime feeding cycle improves metabolic profiles and reduces the risk of obesity, obesity-related conditions such as non-alcoholic fatty liver disease, and chronic diseases such as diabetes and cancer.
In healthy, normal weight, overweight, or obese adults, there is little evidence that intermittent fasting regimens are harmful physically or mentally (i.e., in terms of mood).
It appears that almost any intermittent fasting regimen can result in some weight loss. Among the 13 intervention trials included in this review, 11 (84.6%) reported statistically significant weight loss ranging from 1.3% in a cross-over trial with a 2 week intervention23 to 8.0% in a 1-arm trial of 8 weeks duration.13
Based on only 3 studies, alternate day fasting appears to results in weight loss as well as reductions in glucose and insulin concentrations. However, this pattern may not be practical because of intense hunger on fasting days.
Modified alternate day fasting regimens result in reduced weight, ranging from 3.2% in comparison to a control group16 over a 12 week period to 8.0% in a one-arm trial over an 8 week period.13 There was limited and mixed evidence for reductions in insulin concentrations, improvements in lipids or reductions in inflammatory factors.
Research to date has not demonstrated that alternate day fasting regimens produce superior weight loss in comparison to standard, continuous calorie restriction weight loss plans.
There are limited data from human studies to support the robust rodent data regarding the positive impacts of time-restricted feeding (i.e., eating patterns aligned with normal circadian rhythms) on weight or metabolic health.
There are considerable observational data on various forms of religious fasting, most of which suggests that these regimes result in transitory weight loss with mixed impacts on other biomarkers.
Data are lacking regarding the impacts of intermittent fasting on other health behaviors such as diet, sleep, and physical activity.
There are little or no published data linking intermittent fasting regimens with clinical outcomes such as diabetes, cardiovascular disease, cancer, or other chronic diseases such as Alzheimer’s.
Compared to ad-libitum, but needed a sustained calorie restriction group
A 2-Year Randomized Controlled Trial of Human Caloric Restriction: Feasibility and Effects on Predictors of Health Span and Longevity, The Journals of Gerontology: Series A, Volume 70, Issue 9, 1 September 2015, Pages 1097–1104,
https://doi.org/10.1093/gerona/glv057http://biomedgerontology.oxfordjournals ... /1097.fullAbstract
Background
Caloric restriction (CR), energy intake reduced below ad libitum (AL) intake, increases life span in many species. The implications for humans can be clarified by randomized controlled trials of CR.
Methods
To determine CR's feasibility, safety, and effects on predictors of longevity, disease risk factors, and quality of life in nonobese humans aged 21–51 years, 218 persons were randomized to a 2-year intervention designed to achieve 25% CR or to AL diet. Outcomes were change from baseline resting metabolic rate adjusted for weight change (“RMR residual”) and core temperature (primary); plasma triiodothyronine (T3) and tumor necrosis factor-α (secondary); and exploratory physiological and psychological measures.
Results
Body mass index averaged 25.1 (range: 21.9–28.0kg/m2). Eighty-two percent of CR and 95% of AL participants completed the protocol. The CR group achieved 11.7±0.7 %CR (mean ± standard error) and maintained 10.4±0.4% weight loss. Weight change in AL was negligible. RMR residual decreased significantly more in CR than AL at 12 months (p = .04) but not 24 months (M24). Core temperature change differed little between groups. T3 decreased more in CR at M12 and M24 (p < .001), while tumor necrosis factor-α decreased significantly more only at M24 (p = .02). CR had larger decreases in cardiometabolic risk factors and in daily energy expenditure adjusted for weight change, without adverse effects on quality of life.
Conclusions
Sustained CR is feasible in nonobese humans. The effects of the achieved CR on correlates of human survival and disease risk factors suggest potential benefits for aging-related outcomes that could be elucidated by further human studies.
In Health
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