Higher compared with lower dietary protein during an energy deficit combined with intense exercise promotes greater lean mass gain and fat mass loss: a randomized trial.
Level 2 - randomized trial
Randomized controlled trial
PubMed 26817506 · doi:10.3945/ajcn.115.119339
What was done
A single-blind, randomized, parallel-group prospective trial evaluated 40 young men over a 4-week period. Participants consumed a hypoenergetic diet with an approximate 40% caloric reduction (33 ± 1 kcal/kg lean body mass) and were assigned (n = 20 per group) to either a lower-protein control diet (1.2 g/kg/d) or a higher-protein diet (2.4 g/kg/d). All subjects completed resistance exercise training combined with high-intensity interval training 6 days per week. Body composition was assessed pre- and post-intervention using a 4-compartment model.
What was found
Lean body mass increased significantly in the higher-protein group (1.2 ± 1.0 kg) and to a greater extent than in the control group (0.1 ± 1.0 kg, P < 0.05). Fat mass loss was greater in the higher-protein group (-4.8 ± 1.6 kg) than in the control group (-3.5 ± 1.4 kg, P < 0.05). Exercise performance improved similarly in both groups with no effect of protein level. Changes in serum cortisol correlated with changes in body fat (r = 0.39, P = 0.01) and lean body mass (r = -0.34, P = 0.03).
Why it matters
This trial demonstrates that consuming 2.4 g/kg/d of protein enables concurrent lean mass gain and accelerated fat loss during severe caloric restriction when combined with high-volume exercise.
Limits
The study was short in duration (4 weeks) with a small sample size (n = 40) restricted entirely to young men, limiting generalizability to women, older adults, and longer timeframes. The high-volume supervised training regimen may not reflect free-living conditions.
Cited by
- supports Dietary protein needs increase in a caloric deficit compared to maintenance or energy surplus to preserve muscle mass.