Effect of a medium-term high fat diet on muscle oxidative metabolism in healthy males.

Effect of a medium-term high fat diet on muscle oxidative metabolism in healthy males. Gabriela De Roia, Silvia Pogliaghi Faculty of Motor Sciences, University of Verona, Italy PURPOSE: The study tested the hypothesis that a high fat diet (HFD) enhances oxidative metabolism, by augmenting the muscle capacity to extract oxygen. METHOD: 23 healthy males (28±5 yrs, 53±6 ml*kg-1*min-1) consumed either (#12) a 10-day normocaloric HFD (55, 30, 15% of the total calories from fat, carbohydrate and protein) or (#11) continued their habitual diet (control subjects, C). Before and after the diet, oxidative metabolism was tested non-invasively during an incremental cycling exercise and 3 repetitions of a square-wave exercise of moderate intensity (80% of the first ventilatory threshold). Cardio-respiratory variables were measured breath by breath. Muscle oxygen extraction was measured, at the vastus lateralis, by multiple distance, intensity modulated, near infrared spectroscopy. Maximal (VO2max, muscle oxygen extraction (HHbmax)) and kinetics parameters were calculated at the lung (p, TDp and mean response time (MRTp) of the primary component) and at the muscle levels (m, TDm, MRTm). Means and standard deviations were calculated and compared by t test and Bonferroni correction (p<0.05). RESULTS: HFD and C groups were not different at baseline. No changes were detected in C. After the diet, antropometric values remained unchanged (74±9 Kg, 1,8±0,1 cm, 11±4 % of body fat). While VO2max was unaffected, HHbmax was significantly higher after the HFD (37±9 vs 41±10). During metabolic transitions, at the lungs, p and MRTp were significantly shorter after HFD (21±6 vs 19±6 s; 108±24 vs 96±26 s), with an unchanged TDp (22 ± 4 s). Also at muscle level, MRTm was significantly lower after the HFD (18±3 vs 17±2 s) despite non significant changes in m (9±4 vs 8±5s) and TDm (9±3 vs 9±3). CONCLUTIONS: As a result of HFD, maximal muscle oxygen extraction was significantly increased, yet insufficiently so to affect VO2max. The speed of adaptation of muscle oxidative metabolism, during exercises of moderate intensity (known to be limited primarily by metabolic inertia), was also significantly enhanced by HFD, as evidenced both at the lung and at the muscle levels. Therefore, our data support the hypothesis that a medium-term high fat diet (HFD) enhances oxidative metabolism, in young healthy males, by augmenting the muscle capacity to extract oxygen (peripheral factor). The study was supported by Enervit, Italy.