I'm the best person to answer this for you, I'm an Athlete!!
Your.. uh.. lucky day?
Anyway, if you do happen to do the gym regularly or do some form of workout routine that you will stick too (which you might find easy or hard to stick to, but you MUST have the motivation) then I suggest cutting down on sweets and fatty foods. You can choose what you eat to an extent, but going to the gym and then coming home to eat a big meal, or say, having a big meal before you leave for the gym, that wont work. The thing to do is, have a balanced meal at least 2 hours before you plan to go to the gym or have a workout.
What I do is, weigh out how much, for example, rice to use when having a curry, and so on. Also, I sometimes make up my food at the start of the week so I can just pop it in the microwave. I make up cartons of food which is limited and means I can't eat anymore, which works for me, but may not work for other people who are tempted to eat more food or reach for a snack.
I do treat myself, of course. I love takeaways and chocolate as much as anyone else does. Just if you want to keep in shape, you cant simple "workout" and think that'll be you loosing weight instantly.
Always here for a chat.