'Negative calorie' means that you use more calories in eating and digesting the food than it contains, keeping in mind that we burn calories all of the time by simply living, even when we sleep. In practice the term is used for a lot of low calorie foods.
One of the best known negative calorie foods is celery. It is very low in calories and takes a lot of time and energy to eat, as long as you eat it whole and chew on all of those stringy fibers. If you ate celery in this way all day you would be sure of not gaining weight, but it wouldn't be good for you. You would not be getting the nutrients that you needed and you might even starve.
Negative calorie foods are very popular with anorexics, which shows us that it's not healthy to eat nothing but these foods. However, they make great snacks. To get the best effect for weight loss, be sure to chew them thoroughly and do not make them into soup or juice.
Eat them raw when possible. This is easy with fruits like apples, berries, pineapple and grapefruit which are all low calorie, high fiber foods. Be careful with other fruits because most fruits that are not on this list are more calorie-dense.
Eating vegetables raw is more of a challenge, and not always necessary. However, many foods can be grated or chopped very small in a food processor. Take a look at this list of negative calorie vegetables and you will see that most of them could be prepared for raw eating:
- asparagus (break it into bite sized pieces and add to salad)
- beets (grated)
- broccoli (throw it in the food processor with a couple of tomatoes as dressing)
- carrot (grated or whole)
- cauliflower (like broccoli)
- cabbage (used raw in coleslaw, but don't add the mayo!)
- celery stalks
- celery root (grated)
- red onions (sliced thin)
- zucchini (grate or use a spiralizer to create long pasta-like strings)
A big salad made from 5-7 of those ingredients would give you a super low calorie snack that would keep you munching and feeling full for a long time. You might also want to consider doing a raw or negative calorie detox for a few days - in consultation with your doctor, of course.
However, you will need to use caution when eating a lot of negative calorie foods. First, it is important to vary your diet and not eat too much of any one particular food. Many foods contain substances that can be damaging if consumed in excess, such as the acid in pineapples and grapefruits. Other negative calorie foods can cause allergies or diarrhea if eaten in large quantities.