I've many friends who slimmed down successfully. Here's their
secret.
Many of them told me that don't cut the habit of eating fast food
entirely at the start, slowly cut them down. Slowly, you will break
away from it.
Try to cut down on your food intake, not specifically on what to
eat, what not to eat. A balanced diet is always important. Eat on a
specific time, eat slowly, enjoy your meal. Don't rush through your
meal.
The most important is to exercise regularly. Swimming and gym does
a great job. You don't have to do a tremendous amount in one go.
You just have to strain yourself, the amount is not important. What
is important is that your body feels the strain and the muscles
ache. Also, don't stop entirely when you feel the ache. Try to
continue, but at a slower pace.
If you feel hungry after your exercise, don't eat much, just try to
eat some light snacks and tahan to the next meal, then eat the
balanced diet.
Best of luck.