I have totally eliminated processed foods, junk foods, fast foods and supermarket frozen food from my diet. I eat fresh meat, fish, produce, nuts, yogurt, cheese and eggs daily. I will eat canned or packaged foods but only if they are essentially "whole" foods. For example, sardines packed in olive oil. Or packaged salad mix. If they are loaded with preservatives or corn syrup or any kind of hydrogenated vegetable oils, I don't eat them.
I drink at least four 24-oz bottles of spring water daily along with two cups of English breakfast tea in the morning (with Splenda for sweetener). I also drink beer or wine at dinner. No fruit juice whatsoever. No soda pop. I will have Gatorade or Propel fitness water (made by Gatorade) after a strenous workout.
I walk at least 7 miles daily and more on weekends when time permits. I do 4 miles in the morning, 3 miles at lunchtime and more when I can fit it in. Last Saturday, I walked 18 miles in 4 1/2 hours and then did another 5 miles that afternoon. I won't have many opportunities like that so I took advantage. I also do pushups and situps at night.
To me, exercise is a crucial component of my overall plan to lose weight and keep it off. But the diet is just as important.