If you typically, eat candy bars for snacks, try swapping
the candy
bar for an apple. Keep portion sizes reasonable, and fill up
on complex carbs (veggies) and protein, which take longer to break down, so will keep you feeling fuller, longer.
Make sure you're getting plenty of exercise. Aim for 30 min/day, at least 3 days/week, but if possible, try for 30 min/day 6 days/week. Be sure to combine both cardio and weight training, for the best results.