Eat well before your ride.
Keep hydrated.
Outside of riding - avoid all snacks. If you must, eat a pickle.
Reduce the amount of meat you eat (fish and pork are better than beef). Replace with greens. No butter or salad dressings.
Eat your main meal in the middle of the day, so you have energy for the day.
Eat a small dinner.
Avoid breads, chips, french fries, and other fatty foods.
Fresh fruit and vegetables are okay.