The best place to start is with the diet.... replace the fatty foods with fresh/frozen veggies. Most non starchy veggies have so few calories that they are considered "free", meaning you can eat all you want, without adding unwanted calories. Just don't load them down with cream or cheese sauces, etc.
Eat plenty of lean protein, either in the form of lean meats, chicken, fish, eggs, etc. Opt for low fat dairy, including milk, yogurt, cheese.