Some athletes are consuming higher fat and protein diets, but many are viewing them with caution due to potential negative performance and health consequences, including increased adiposity and increased risk of coronary artery disease.
M.B. Wallace, Evolution Sports Science, Human Performance Center, Waltham, MA, examined the effects of a high fat (52% of total calorie intake from fat, 30% carbohydrate) versus a high carbohydrate (16% of total calories from fat, 70% carbohydrate) diet on plasma lipid and lipoproteins, body fat, aerobic capacity and lean body mass in 28 endurance trained triathletes over a period of 15 weeks. Various measures of blood cholesterol levels, aerobic capacity, bone mineral density and body composition were measured at baseline and after 5, 10 and 15 weeks.
Total and percent body fat, lean tissue mass, body weight and total body bone density were not significantly different within and between each group from baseline to week 15. Changes in lipids and lipoproteins; from baseline to week 15 did not differ between the two groups except in HDL cholesterol which decreased significantly and triglycerides which increased significantly in the high carbohydrate group.
The authors concluded that during periods of endurance training when energy requirements were high, increasing the percentage of fat in the diet of well-trained triathletes to approximately 52% of total calorie intake did not increase body weight or fat gain and did not result in adverse changes to the lipoprotein profile, aerobic capacity and body composition.