Took this from my Body-for-Life book on eating.  Please ignore the typo's as it is late. 

Bill Phillips wrote...

Myth:  If you exercise, it doesn't matter what you eat.

Fact:  If you exercise, it matters EVEN MORE what you eat.

"More Americans are exercising now than ever before.  And that's got to be good news, right?  We must be making up for those high-fat, high-calorie diets with the positive effects of exercise because those effects are just, well, so positive. 

Think agian.  Despite the fact that more and more people are giving exercise a try, we're still seeing a rapid increas in the number of Americans who are obese and who are suffering from health problems caused by being very 'unfit."

In fact, there are in excess of 58 million clinically obese men and women in America today, and we spent more than $100 BILLION last year alone to treat diseases such as cancer, diabeters, stroke, heart disease, and other ailments that are caused, more often than not, by a lack of "finess."

What I see are literally million of people who are completely overlooking the fact that Physically active individuals need MORE nutrients than there sedentary counterparts.  So many people are mis-informed about this topic.  I wish I could go into every fitness center in North America and tell every single person who's exercising - whether they're walking or running, swimming or spinning, lifting weights or whatever - that without optimal levels of the nutrients your body needs, you are not going to get the results you are looking for.  If you're anything like me, you are exercising to create a positive result, not becasue you've got nothing better to do.  In fact, you may be doing more harm than good because when you are exercising a nutrient-deficient body, you're not making it healthier: You're actually creating a worse nurtient deficiency. 

Believe me, folks, I've tested this thing every way to Sunday.  I know thousands of people, many of whom are probably just like you, who had all but given up on ever discovering how to successfully transfomr their physiques.  Many of them had the technical informatin on nutrition and exercise but couldn't cross that abyss we talked about earlier.  Others had a reson, they set a goal, and they were prepared to cross the abyss, but they didn't have the correct infrmation - they had misinformation.  In every case, something was missing, and the person was left believing the "Exercise only works for people with the right genetice," or "There's something wrong with my system," or "I must have a thyroid hormone problem or something."

I mean, let's face it.  If we give something a solid effort, if we really put our hearts and soul into it, not just once but time and time agian, and it still doesn't work, eventually we're going to get frustrated and give up.  working hard and going nowhere is unrewarding and dispiriting.  It's downright frustrating. 

The bottom line is this:  If you don't have the nutrients in your system to recover, much less improve, following intense exercise, it's like you're flickering a lighter with no butane - you might get a spark but no flame.  You have to have both - the fuel and the spark.   You have to have the material for that fire to burn, and you have to have the spark to create the flame. 

Essentially, there are a bunch of people out there with blisterd thumbs just slapping away at a lighter and burning out the flint because there's no fuel in their bodies to create combustion.  The result, naturally, is frustration.  Imagine if you were holding a lighter and you just sat there goining flick, flick, flick, flick - and nothing happened.

Eventually you'd say, "Screw this.  This lighter doesn't work." And you'd throw the thing away.  well, this is what too many people do with the idea of exercise.  They give it a go, without feeding themselves properly, and then they quit trying. 

However, it doesn't have to be that way.  By not becoming a victim of the myth that exercise alone is all you need to get fit - by accepting the fact that optimal nutrition is just as important as exercsie - you will be one step closer to achieving the level of success you rightfully deserve."