Nancy Clark, M.S., R.D., is the nutrition counselor at SportsMedicine Brookline. Just a thought. I did some reading which I found very interesting. Both of these books report a great deal of research that isn't cited much elsewhere. For example, they quote numerous studies showing that the way fats are processed and cooked can be more injurious to health than the fats themselves.
Hydrogenated fats are the worst.
My own experience confirms this. Others have a very detrimental effect on my ability to process oxygen, e.g. olive oil which is a high-monounsaturated fat source. Mono-unsaturated fats are known to clog small blood vessels, preventing oxygen from getting through. So, there are different fats that may have very different effects on performance. Karl King I'd like to add to what Rich said.