The influence of fasting and energy-restricted diets on leptin and adiponectin levels in humans: A systematic review and meta-analysis

Abstract

Fasting and energy-restricted diets have been evaluated in several studies as a means of improving cardiometabolic biomarkers related to body fat loss. However, further investigation is required to understand potential alterations of leptin and adiponectin concentrations. Thus, we performed a systematic review and meta-analysis to derive a more precise estimate of the influence of fasting and energy-restricted diets on leptin and adiponectin levels in humans, as well as to detect potential sources of heterogeneity in the available literature. A comprehensive systematic search was performed in Web of Science, PubMed/MEDLINE, Cochrane, SCOPUS and Embase from inception until June 2019. All clinical trials investigating the effects of fasting and energy-restricted diets on leptin and adiponectin in adults were included. Twelve studies containing 17 arms and a total of 495 individuals (intervention=249, control=246) reported changes in serum leptin concentrations, and 10 studies containing 12 arms with a total of 438 individuals (intervention=222, control=216) reported changes in serum adiponectin concentrations. The combined effect sizes suggested a significant effect of fasting and energy-restricted diets on leptin concentrations (WMD:-3.690ng/ml, 95% CI:-5.190,-2.190, p≤0.001; I2=84.9%). However, no significant effect of fasting and energy-restricted diets on adiponectin concentrations was found (WMD:-159.520ng/ml, 95% CI:-689.491, 370.451, p=0.555; I2=74.2%). Stratified analyses showed that energy-restricted regimens significantly increased adiponectin (WMD: 554.129ng/ml, 95% CI: 150.295, 957.964; I2=0.0%). In addition, subsequent subgroup analyses revealed that energy restriction, to ≤50% normal required daily energy intake, resulted in significantly reduced concentrations of leptin (WMD:-4.199ng/ml, 95% CI:-7.279,-1.118; I2=83.9%) and significantly increased concentrations of adiponectin (WMD: 524.04ng/ml, 95% CI: 115.618, 932.469: I2=0.0%). Fasting and energy-restricted diets elicit significant reductions in serum leptin concentrations. Increases in adiponectin may also be observed when energy intake is ≤50% of normal requirements, although limited data preclude definitive conclusions on this point.