which is THE best dieting PLAN?

im 14 years old, 159cm and 112 pounds/50kg.
i know that some of you may say at this age i dont need to worry, but i wanna at least maintain this weight for a while. BECAUSE I EAT A LOT, i have been trying a couple things to get rid of my belly and excess fat on my thighs. but when i start doing research, everything just muddles up my brain.

recently in a time magazine, it says excercise won’t make you skinny. in this website, fatloss4idiots.com or something, it says low-carb and low-calorie diets NEVER work. in others, it says it does. so my question is: WHAT?!!! whats the best way to MAINTAIN your weight, or lose a couple pounds off a certain area of your body? ive recently taken up spin cycling, for my thighs and i try to do sit-ups everyday. will this help at all? i already do regular excercise around twice a week.

and is eating the right foods really the key? if so, what? like for breakfast, say..eggs on toast? any advice would help, thank you

ps. its not, NOT that i think im fat, i would just feel happier with myself if i lost this belly of mine.