Purpose: Athletes risk performance and muscle loss when dieting. Strategies to prevent losses are unclear. This study examined the effects of two diets on anthropometrics, strength, and stress in athletes.
Methods: This double-blind crossover pilot study began with 14 resistance-trained males (20-43 yr) and incurred one dropout. Participants followed carbohydrate-matched, high-protein low-fat (HPLF) or moderate-protein moderate-fat (MPMF) diets of 60% habitual calories for 2 weeks. Protein intakes were 2.8g/kg and 1.6g/kg and mean fat intakes were 15.4% and 36.5% of calories, respectively. Isometric midthigh pull (IMTP) and anthropometrics were measured at baseline and completion. The Daily Analysis of Life Demands of Athletes (DALDA) and Profile of Mood States (POMS) were completed daily. Outcomes were presented statistically as probability of clinical benefit, triviality, or harm with effect sizes (ES) and qualitative assessments.
Results: Differences of effect between diets on IMTP and anthropometrics were likely or almost certainly trivial, respectively. Worse than normal scores on DALDA part A, part B and the part A "diet" item were likely more harmful (ES 0.32, 0.4 and 0.65, respectively) during MPMF than HPLF. The POMS fatigue score was likely more harmful (ES 0.37) and the POMS total mood disturbance score (TMDS) was possibly more harmful (ES 0.29) during MPMF than HPLF.
Conclusions: For the 2 weeks observed, strength and anthropometric differences were minimal while stress, fatigue, and diet-dissatisfaction were higher during MPMF. A HPLF diet during short-term weight loss may be more effective at mitigating mood disturbance, fatigue, diet dissatisfaction, and stress than a MPMF diet.