Does Adaptive Thermogenesis occur after weight loss in adults? A systematic review

Adaptive thermogenesis (AT) has been proposed to be a compensatory response that may resist weight loss(WL) and promote weight regain. This systematic review examined the existence of AT in adults after a period of negative energy balance with or without a weight stabilization phase. Studies published until May 15th, 2020 were identified from PubMed, Cochrane Library, EMBASE, MEDLINE, SCOPUS and Web of Science. Inclusion criteria included: statistically significant WL; observational with follow-up or experimental studies; age>18years; sample size≥10 participants; intervention period ≥1week; published in English; objective measures of total daily energy expenditure(TDEE), resting energy expenditure(REE) and sleeping energy expenditure(SEE). The systematic review was registered at PROSPERO(2020 CRD42020165348). A total of 33 studies comprising 2528 participants, were included. AT was observed in 27 out of 33 studies. Twenty-three studies showed significant values for AT for REE(82.8%), 4 studies for TDEE(80.0%) and 2 studies for SEE(100%). A large heterogeneity in the methods used to quantify AT and between subjects and among studies regarding the magnitude of WL and/or of AT was reported. Well-designed studies reported lower or non-significant values for AT. Overall, these findings suggest that although WL may lead to AT in some of the EE components, these values may be small or non-statistically significant when higher-quality methodological designs are used. Furthermore, AT seems to be attenuated, or non-existent, after periods of weight stabilization/neutral energy balance. Therefore, more high-quality studies are warranted not only to disclose the existence of AT, but to understand its clinical implications on weight management outcomes.