The food you consume will over time have an effect on your bodies ph.
A simple example is heartburn. This is a symptom of the body being too acidic.
An acidic body will eventually break down and become sick.
Unfortunately most sport or body building nutrition advice revolves around macronutirent ratio arguments.
How much fat, carbs and protein should I eat?
Well thats a great start but if you want to get your engine truly running at its peak then you need to understand the acidic nature of the foods you eat and also the thermic properties.
for a list of acidic and alkaline foods try here:
Food PH Chart - Most Alkaline and Acidic Foods
Some foods are extremely cooling to the body like bean sprouts and water melon and some foods are very warming to the body like garlic, ginger and lamb.
Excessive consumption in one direction or another will lead to symptoms along the lines of that food. example: Raw fruits and vegetables possess cool energy. According to traditional Chinese medicine, overconsumption can result in symptoms such as chilliness, mucus, congestion, fatigue and depletion, feeling cold, abdominal pain, poor appetite and bloating after meals. This is why most chinese food has garlic and ginger in it.. To make the vegetables more warming.
Too many foods with a hot thermic property will lead to constipation, sluggish digestion, high blood pressure, hot red face etc etc
These are all principles of Traditional Chinese Medicine of which my wife is a practitioner.
If you would like to know more then check out the iphone app Qifood for a start or look up warming and cooling foods in google.
The bible on the subject of food and its healing nature on the body would be:
Healing with whole foods by Paul Pitchford