Q: If fat provides more calories than carbs, why is a high fat diet is not as good as a high carb diet. Just to be clear ? I?am talking about active people ? like athletes eating an energy rich diet ? obviously even too many carbs if not used will turn to fat.

A: The main reason is that carbs (in the form of blood glucose or muscle glycogen) are 'preferred' by your muscles (and some organs like the brain) and are necessary for maximum efforts which last more than a few seconds but less than about two minutes. Such efforts are typical of many if not most sports and bodybuilding-type weight training (a weightlifting set usually lasts 20-40 seconds). While muscles can and do use fatty acids for fuel, especially for long duration efforts, peak performance in most sports requires such short-term intense efforts and therefore atheletes benefit from a carb-rich diet.