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Old 03-24-2009, 01:57 PM   #9
Donald Lee
Senior Member
Join Date: Mar 2008
Posts: 620

This study might be useful, but it's for endurance athletes:

It has been shown that high CHO (60% to 70%) and low-fat (10% to 15%) diets enhance endurance performance, and high-fat diets (60%) are detrimental to performance. Athletes eating high-carbohydrate (low-fat) diets do not consume as many calories as they expend and may not meet the ADA levels of iron and zinc. Recent data, also, indicate that diets comprising 32% to 55% fat can improve endurance capacity compared to diets with 15% fat. There is evidence that fit subjects have higher fat oxidation due to increased enzyme levels, fatty acid transport and beta oxidation. In addition, intramuscular triglycerides and intracellular fats can be increased by a high-fat diet and can support higher levels of fat oxidation without compromising CHO stores. It is clear that if CHO intake is reduced to below 20% of total calories, or to less than 1.9 g/kg/day, glycogen stores are compromised and therefore performance will be compromised. Similarly, reducing fat intake to less than 20% of total calories compromises fat stores and therefore endurance performance.

It appears that a critical issue regarding the role of diet in exercise is that total caloric intake must be balanced to total caloric expenditure. Furthermore, the substrates consumed should replenish the intramuscular stores of the substrates used during training and competition. In trained athletes eating isocaloric diets that have sufficient levels of fats and CHOs (muscle stores), our data suggest that the blend of fats and CHOs used during exercise is set by the intensity of the exercise and is constant throughout the exercise time. Most scientists agree that a diet containing 15% to 20% protein calories is sufficient to meet the protein demands of most athletes. Thus a general isocaloric diet should comprise 30% to 35% CHOs, 30% fats and 20% protein, with the balance (20%) of total calories supplying the substrates used in training and competition. For competitions requiring exercise intensities of up to 85% of Vo2max, dietary fats may be more beneficial. For exercise intensities above 100% of Vo2max, CHOs would be the preferred macronutrient. The ratio of the intake of fats and carbohydrates to optimize performance for exercise between 80% to 100% Vo2max remains to be investigated.
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