If you enjoy snacking but do not want to pack on the pounds, remember that you should stay active after a snack. If you sneak a candy bar here and there, it's not the end of the world. Just remember to get out and mow the lawn, take the dog for a walk, ride your bike a few miles, or any other activity that helps you make use of those calories.
To become thinner, you should consider exercising. If you start eating healthier foods, you are going to lose weight but exercising allows you to get thinner much faster. Try exercising for half an hour every day and perhaps for a couple of hours every weekend. You could go for a walk or a jog, if you do not like weight lifting.
If you are trying to lose weight, avoid food with MSG. MSG is most common in Asian food and canned soup. Look for restaurants that say "No MSG" on the menu or for soups that have "No MSG" on their label. This ingredient deters your brain from sending a "full" signal to your stomach and can cause you to eat more than you originally intended to.