Time-restricted eating with energy restriction modestly improves fat mass loss in severe obesity: the MACRO randomised clinical trial

Abstract This 12-wk randomised trial evaluated weight loss, body composition changes and metabolic responses to a time-restricted eating with energy restriction (TRE + ER) diet in adults with severe obesity. One hundred participants (20–60 years; BMI > 40 kg/m 2 ) were randomised to TRE + ER ( n 50; eating window 10 am–6 pm) or continuous energy restriction (CER, n 50). Diets provided 60 % of total energy expenditure. Body composition, by DXA, and RMR, by indirect calorimetry, were assessed at baseline and after 1, 5, 9 and 12 wk. Subjective appetite ratings and biochemical markers were also determined. After 12 wk, both groups experienced reductions in body weight, fat mass (FM) and visceral adipose tissue (VAT), with no significant change in fat-free mass. Compared with CER, TRE + ER produced similar reductions in weight (−4·3 ± 0·4 kg v. −3·8 ± 0·4 kg; P = 0·46) and VAT (−270 ± 4 g v. −188 ± 4 g; P = 0·24), but greater FM loss (−3·5 ± 0·3 kg v. −2·4 ± 0·3 kg; P = 0·040). TRE + ER showed a greater decline in RMR ( P = 0·032) and a trend towards greater adaptive thermogenesis ( P = 0·061). Our findings suggest that combining ER with the TRE strategy does not enhance weight loss, despite the modestly greater FM loss after 12 wk. The greater decline in RMR and the greater increase in adaptive thermogenesis suggest limited long-term benefit of the TRE strategy in individuals with severe obesity. Registered at REBEC (RBR-45fpgqh – https://ensaiosclinicos.gov.br/rg/RBR-45fpgqh ).