Since you are growing, you may find that you are more hungry, or are hungry more often. This is perfectly normal, as long as you need the extra calories to grow.
Overeating and not exercising can lead to unhealthy weight and body conditions. Obesity is defined as having 20% more than the "ideal" body weight for someone your age and height. If you think that you may be overweight or obese, talk to your parents or doctor about ways to become healthier.
If you want to eat healthy, it is important to make healthy choices in what you eat all the time – meaning: meals and snacks.
For example: foods with refined grains, such as white flour or refined wheat, have high amounts of starch that the body just stores away and doesn't use. Try to eat more whole grains such as whole wheat (bread, etc.), brown rice, and oats – which provide energy over a longer period of time after you eat them.