I know that many people are not into exercises, but really, you can sign up for gym or find something on the internet you think is suitable of exercises. Running
and walking is very good. Definitely cut out fast
food and too much candy/chocolate/etc. Of course, it's not like it's not allowed, just don't overdo it.
If you're really not an exercise friend, you can try what I did and another girl who succeeded did. Eat two teaspoon of honey right before going to sleep.