More activity, less television, less soda, less sweets. Adding a little exercise can make a big difference IF you do it consistently. Set small goals for yourself- drink one less soda per day, spend an extra 5 minutes a day walking- just little things that you can easily turn into a habit. And don't stress over your weight. At your age, you've likely not had your 'growth spurt' yet. Odds are, your height will increase a few inches in the coming years, and the 144 pounds won't seem quite so large. DO NOT weigh yourself every day. You didn't gain the weight in a week, and you won't lose it in a week, either. Patience and consistency. Enjoy your life.