A 7-day high protein hypocaloric diet promotes cellular metabolic adaptations and attenuates lean mass loss in healthy males

Mitochondrial quantity and density are associated with increased oxidative metabolism. It has been demonstrated that a hypocaloric high fat/low carbohydrate (HF/LC) diet can up-regulate transcriptional markers of mitochondrial biogenesis; this was yet to be explored in vivo subsequent to a high protein/low carbohydrate (HP/LC) diet. Thus the aims of the study were to explore such diets on transcriptional markers or mitochondrial biogenesis, body composition and resting metabolic rate (RMR). Forty-five healthy male participants were randomly assigned one of four intervention diets: eucaloric high protein low carbohydrate (PRO-EM), hypocaloric high protein low carbohydrate (PRO-ER), eucaloric high carbohydrate (CHO-EM) or hypocaloric high carbohydrate (CHOER). The macronutrient ratio of the high protein diet and high carbohydrate diets was 40:30:30% and 10:60:30% (PRO:CHO:FAT) respectively. Energy intake for the hypocaloric diets were calculated to match resting metabolic rate. Participants visited the laboratory on 3 occasions each separated by 7 days. On each visit body composition, resting metabolic rate and a muscle biopsy from the vastus lateralis was collected. Prior to visit 1 and 2 habitual diet was consumed which was used as a control, between visit 2 and 3 the intervention diet was consumed continuously for 7-days. No group time effect was observed, however in the PRO-ER group a significant increase in AMPK, PGC-1a, SIRT1 and SIRT3 mRNA expression was observed post diet intervention groups (p < 0.05). No change was observed in any of the transcriptional markers in the other 3 groups. Despite ~30% reduction in calorie intake no difference in lean mass (LM) loss was observed between the PRO-ER and CHO-EM groups. The results from this study suggest that a 7-day a high protein low carbohydrate hypocaloric diet increased AMPK, SIRT1 and PGC-1 a mRNA expression at rest, and also suggest that increased dietary protein may attenuate LM mass loss in a hypocaloric state.