Purpose
Despite adaptive thermogenesis (AT) being studied as a barrier to weight loss (WL), few studies assessed AT in the resting energy expenditure (REE) compartment after WL maintenance. The aim of this study was twofold: (1) to understand if AT occurs after a moderate WL and if AT persists after a period of WL maintenance; and (2) if AT is associated with changes in body composition, hormones and energy intake (EI).
Methods
Ninety-four participants [mean (SD); BMI, 31.1(4.3)kg/m2; 43.0(9.4)y; 34% female] were randomized to intervention (IG, n = 49) or control groups (CG, n = 45). Subjects underwent a 1-year lifestyle intervention, divided in 4 months of an active WL followed by 8 months of WL maintenance. Fat mass (FM) and fat-free mass (FFM) were measured by dual-energy X-ray absorptiometry and REE by indirect calorimetry. Predicted REE (pREE) was estimated through a model using FM, FFM. EI was measured by the “intake-balance” method.
Results
For the IG, the weight and FM losses were − 4.8 (4.9) and − 11.3 (10.8)%, respectively (p < 0.001). A time–group interaction was found between groups for AT. After WL, the IG showed an AT of -85(29) kcal.d−1 (p < 0.001), and remained significant after 1 year [AT = − 72(31)kcal.d−1, p = 0.031]. Participants with higher degrees of restriction were those with an increased energy conservation (R = − 0.325, p = 0.036 and R = − 0.308, p = 0.047, respectively). No associations were found between diet adherence and AT. Following a sub-analysis in the IG, the group with a higher energy conservation showed a lower WL and fat loss and a higher initial EI.
Conclusion
AT in REE occurred after a moderate WL and remained significant after WL maintenance. More studies are needed to better clarify the mechanisms underlying the large variability observed in AT and providing an accurate methodological approach to avoid overstatements. Future studies on AT should consider not only changes in FM and FFM but also the FFM composition.
CORE (COnnecting REpositories)
CORE (COnnecting REpositories)