Aim: 

Animal and human studies suggest that a medium-term a high fat diet has the potential to induce structural and functional muscle adaptations that may lead to an enhanced oxidative metabolism. We tested the hypothesis that a medium term high-fat normocaloric diet enhances oxidative metabolism by augmenting the muscle's capacity to extract oxygen (peripheral factor).

Methods: 

20 young healthy moderately trained males (29 6 yrs, 75 9 Kg, 176 7 cm, 11 3% body fat, 53 7 ml*Kg^-1*min^-1 VO_2max) were randomly divided in two subgroups and consumed either a normocaloric high-fat diet (HFD, 55% of calories from fat, 30% carbohydrate and 15% proteins) or a control normocaloric diet (C, 25, 60 and 15%) for 10 days.

Before (pre) and after the diet (post), the subjects performed an incremental cycling test to exhaustion. Respiratory variables and heart rate (HR) were measured breath by breath (Quark b2, Cosmed) and the concentration of deoxygenated hemoglobin ([deoxyHb]) was measured non-invasively at the vastus lateralis, using near-infrared spectroscopy (Oxiplex Ts, ISS). Maximal oxygen consumption (VO_2max) and maximal muscle O₂ extraction ([deoxyHb]_max) were calculated as the average of the last 10 s upon exhaustion. Average standard deviation were calculated for all parameters and data were compared by t test and Bonferroni correction. Statistical significance was set at p < 0.05.

Results: 

Subjects on HFD and C diet did not differ at baseline for any of the measured parameters. Maximal muscle O₂ extraction ([deoxyHb]_max) was 40 11 mmol*l^-1 at baseline. Subjects did neither gain nor loose weight or % body fat as a result of the diets. Furthermore, VO_2max and maximal muscle O₂ extraction ([deoxyHb]_max) were unaffected by diets.

Conclusions: 

The maximal functional level of oxidative metabolism, as measured by VO_2max and maximal O₂ extraction, is neither increased not decreased by a 10-days high fat normocaloric diet in young healthy, moderately trained subjects. Therefore, our data do not support our initial hypothesis.