High Compared with Moderate Protein Intake Reduces Adaptive Thermogenesis and Induces a Negative Energy Balance during Long-term Weight-Loss Maintenance in Participants with Prediabetes in the Postobese State : A PREVIEW Study

Background: Weight loss has been associated with adaptations in energy expenditure. Identifying factors that counteract these adaptations are important for long-term weight loss and weight maintenance. Objective: The aim of this study was to investigate whether increased protein/carbohydrate ratio would reduce adaptive thermogenesis (AT) and the expected positive energy balance (EB) during weight maintenance after weight loss in participants with prediabetes in the postobese state. Methods: In 38 participants, the effects of 2 diets differing in protein/carbohydrate ratio on energy expenditure and respiratory quotient (RQ) were assessed during 48-h respiration chamber measurements similar to 34 mo after weight loss. Participants consumed a high-protein (HP) diet In = 20; 13 women/7 men; age: 64.0 +/- 6.2 y; BMI: 28.9 +/- 4.0 kg/m(2)) with 25:45:30% or a moderate-protein (MP) diet (n = 18; 9 women/9 men; age: 65.1 +/- 5.8 y; BMI: 29.0 +/- 3.8 kg/m(2)) with 15:55:30% of energy from protein:carbohydrate:fat. Predicted resting energy expenditure (REEp) was calculated based on fat-free mass and fat mass. AT was assessed by subtracting measured resting energy expenditure (REE) from REEp. The main outcomes included differences in components of energy expenditure, substrate oxidation, and AT between groups. Results: EB (MP = 0.2 +/- 0.9 MJ/d; HP = -0.5 +/- 0.9 MJ/d) and RO (MP = 0.84 +/- 0.02; HP = 0.82 +/- 0.02) were reduced and REE (MP: 73 +/- 0.2 MJ/d compared with HP: 78 +/- 0.2 MJ/d) was increased in the HP group compared with the MP group (P <0.05). REE was not different from REEp in the HP group, whereas REE was lower than REEp in the MP group (P <0.05). Furthermore, EB was positively related to AT (r(s) = 0.74; P <0.001) and RQ (r(s) = 0.47; P