Food
Yah what you eat is important. During my quest for improved health, I tried a bunch of different approaches - high carb/low fat; lacto-vegetarian; vegan; soy; high protein/low carb; and balanced.
For me, what eventually worked is a diet high in vegetables, fat, seeds/nuts and protein but low in carbohydrates. The more vegetables and vegetable fat the better. I still occasionally eat unprocessed carbs like brown rice, beans and lentils (except for that damn cheese popcorn - curse you Old Dutch). However, I avoid white bread, cereal, white rice, crackers, cookies, cakes, pastries, chips, soda, sugar and similar products. By avoiding processed carbs, I find my energy levels are much more stable throughout the day and feel much better overall. Personally, I think this dietary approach will work for most people.
I think that for all people, the eating of processed carbs, especially sugar, is asking for health problems. Problems ranging from heart disease to diabetes and obesity are a certainty, unless you pay attention to what you eat.
The critical thing I've learned about diet is that it has small effects in the short term that become amplified over time. Heart disease, diabetes, arthritis etc. result from 20-30-40 years of accumulated small abuses.