Fruit

According to registered dietitian Keri M. Gans, fruit can satisfy a craving for sugar without too many calories. For snacks that are just at or under 50 calories, try half of a small banana, 12 fresh cherries, 14 seedless red grapes, 3/4 cup of raspberries, eight strawberries or a 50-calorie sugar-free applesauce snack cup. If you're craving something cold, try the fruit frozen or have a 50-calorie fruit juice pop.

Vegetables

Vegetables are a good snack pick because they're so low in calories, you can eat enough of them to fill up on appetite-suppressing fiber, in addition to getting a dose of vitamins and minerals. Some 50-calorie or less choices include seven stalks of celery, a half-cup of carrots served with 1 tablespoon of low-fat ranch-style dressing, 10 spears of cooked asparagus, 40 sugar snap peas or half-cup of sliced raw jicama with 4 ounces of salsa.

Protein

Kate Harrison, the author of "The 5:2 Diet Book," recommends including some lean protein choices in your 50-calorie snack repertoire. Protein-rich snacks can help keep you feeling full for a longer time than low-protein foods. Harrison suggests a slice of ham, an omelet prepared from two egg whites, 1 ounce of smoked salmon on two wheat crackers or 1 ounce of cooked prawns, all of which contain about 50 calories. You can also try a quarter-cup of shelled edamame, half-cup of fat-free yogurt topped with 1 teaspoon of sunflower seeds, two slices of white turkey meat or eight dry-roasted peanuts.

Grains

When it's carbohydrates you want to snack on, pick whole-grain choices over products made with refined grains. The complex carbohydrates and fiber in whole grains will help keep your blood sugar level steady. A large whole-grain pretzel rod has 37 calories, while a brown rice cake spread with 1 tablespoon of sugar-free jam has 44 calories. A 3-cup serving of air-popped popcorn is also less than 50 calories, though remember not to add butter or to sprinkle on too much salt.

Sweets

If you can't resist the temptation to have a sweet treat, try five pieces of sugar-free hard candy, 20 sugar-free jelly beans, a square of dark chocolate, a small scoop of low-fat vanilla ice cream, a sugar-free gelatin cup topped with 3 tablespoons of light whipped topping or one sugar-free fudge ice pop. All of these snacks will provide you with approximately 50 calories or less, as long you keep the portion size under control.