Healthiest ultra-low calorie snacks?

Look up negative calorie foods and it will give you a list of really low calorie fruits and veggies.

Fruits and veggies!

A medium apple, cup of strawberries, or 1/2 small banana are ones I know are 50 calories or less. Baby carrots, cucumbers, cherry tomatoes... yum! Or 1/2 cup of yogurt, depending on brand.

a stick of celery is 10 calories but uses 10% more to digest in your body

http://www.burnthefat.com/negative_calorie_food.html

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