Changes in body fat percentage during body weight stable conditions of increased daily protein intake vs. control

ObjectiveThe objective of this study was to examine if increased protein intake vs. control influences body fat percentage during stable body weight.DesignBody composition was assessed before and after a 3-month isoenergetic dietary intervention of 2MJ/d supplements exchanged with 2MJ/d of habitual ad libitum energy intake. The parallel design consisted of protein-rich supplements in the protein group (n = 12) and an isoenergetic combination of carbohydrate and fat supplements in the control group (n = 12). Daily protein intake was calculated from a 24 h urinary nitrogen. Body composition was measured by a combination of underwater-weighing technique, deuterium-dilution technique and whole-body dual-energy X-ray absorptiometry (DXA), a method that allows for estimation of 4-body compartments (fat and lean; water, bone and rest).ResultsSubjects were weight stable and did not change their habitual physical activity. Daily protein intake increased in the protein group during the intervention compared to baseline with + 11 ± 14 g (P < 0.05) vs. the control group that did not change their protein intake − 1 ± 15 g. This resulted in a significant difference in protein intake during the intervention of 80 ± 21 g of the protein group vs. 59 ± 11 g of the control group (P < 0.01). Change in body fat percentage showed a significant group × time interaction of decreased body fat percentage of − 1.0 ± 1.1% of the protein group vs. 0.1 ± 0.6% of the control group (P < 0.05). The group × time interaction of change in fat mass was significant (P < 0.05), and change in fat-free mass was a trend (P = 0.05). Fat-free mass of the protein group had increased with + 0.9 ± 0.6 kg (P < 0.01), and fat mass had decreased with − 0.6 ± 0.8 kg (P < 0.05), while the control group had not changed.ConclusionDuring increased daily protein intake vs. control body fat percentage decreased with unchanged physical activity during 3 months of stable body weight.