Your body uses energy to digest food, and that means calories. Chewing, swallowing, digesting, and absorbing your snacks causes your body to burn a small number of calories every time you eat.
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In most cases, this isn’t enough to balance out the calories you take in from eating the food, but there are a few healthful foods that actually have negative calories. While medical professionals agree that you should never try to make a diet consisting entirely of negative-calorie foods, since in some ways it’s even worse than eating nothing at all, they make excellent choices for snacks, side dishes, sandwich fillers, and so on.
Probably the most famous negative-calorie food, celery is mostly water and contains a scant six calories per stalk. You might think that a vegetable with such a low calorie count would provide a similarly small number of vitamins and minerals, but in truth, celery is an excellent source of vitamin K, which helps your blood to clot properly, and potassium, which lowers your blood pressure and reduces your risk of heart attack and stroke.
Although celery has the brightest reputation as a negative-calorie food, lettuce may actually be more deserving of the crown. With 95% water content, iceberg lettuce is little more than crunchy water, and each leaf only provides a single calorie. The downside? Because iceberg lettuce has so little to it besides water, it doesn’t provide the vitamins and minerals of some other negative-calorie foods. Other sorts of lettuce, like romaine and radicchio, have more nutritional value but also more calories, although admittedly, “more” isn’t a whole lot in this case. A leaf of romaine lettuce may pack five times the calories of a leaf of iceberg, but it’s still a lower-calorie choice even than celery.
Spinach may have less water than iceberg lettuce, but it has even fewer calories; a cup of spinach has seven calories, as opposed to eight for iceberg lettuce. What’s more, spinach is a superfood for good reason. Raw spinach is a spectacular source of iron, vitamin C, and vitamin A, and it also provides such critical nutrients as folate, vitamin K, calcium, and vitamin B6. Eating spinach can not only fill you up without giving you calories, but can also give you a healthful dietary boost without making you turn to higher-calorie foods like meat and dairy.
You’ve seen the cliche pictures of pampered spa clients with cucumbers on their eyes. Part of the cucumber’s reputation as an eye pad comes from their incredibly high water content – at 96% water, they’re as much “crunchy water” as iceberg lettuce is. Half a cup of sliced cucumbers will only give you eight calories. What’s more, while cucumbers don’t provide as many traditional nutrients as celery or spinach, they’re chock-full of antioxidants, which scavenge the free radicals that cause cancer, heart disease, Alzheimer’s, vision loss, and countless other chronic age-related conditions.
An entire medium zucchini is just 33 calories . That’s more than celery, but a zucchini also has nearly five times the potassium content of a stalk of celery and has more vitamin C than a tangerine. An added bonus: you can use grated zucchini, or “zoodles,” in place of pasta , getting your noodle fix with negative calories. Zucchini is a great source of fiber as well, which helps to lower your blood sugar and cholesterol levels. In addition, fiber-rich foods fill you up faster than low-fiber ones, so your stomach won’t know that you’re only eating 33 calories.
Speaking of pasta, don’t be afraid to throw some tomato sauce on those zoodles. Like a single zucchini, a single tomato has just 33 calories . At 94% water, it has only slightly less water content than iceberg lettuce, but is far richer in nutrition. Tomatoes are most famous as a source of lycopene, a powerful antioxidant which may reduce your risk of cancer, heart disease, and certain eye disorders related to aging. Tomatoes are also an excellent source of both vitamins A and C, as well as dietary fiber.
With double your daily requirement of vitamin A, there’s no question that carrots are as good for your eyes as their reputation suggests. They’re also incredibly low in calories – just 25 calories for a medium carrot. What’s more, that high vitamin A content is good for more than just your eyes. Vitamin A has antioxidant properties and helps with the health of your skin, bones, and teeth, so a carrot dramatically improves your overall well-being without throwing in any calories. Carrots are also a solid source of potassium and dietary fiber.
Not all negative-calorie foods are vegetables. Cold, sweet watermelon does have more calories than most of the negative-calorie vegetables because of its fructose content; a cup of diced watermelon is 46 calories, which seems downright fattening compared to spinach and celery. However, a 2012 study showed that watermelon can actually help with weight loss. In the study, mice that drank water with added watermelon juice gained less weight and had lower levels of “bad” LDL cholesterol than mice that drank water without it. This may be because watermelon has high levels of an amino acid called citrulline. Watermelon is also a powerhouse of vitamins A and C, providing about a third of your daily requirements with a single serving.
9. Oranges, Tangerines, And Grapefruit
Next time you want a sweet snack and aren’t in the mood for watermelon, try reaching for citrus. Oranges, tangerines and grapefruit are best known as rich sources of immune-boosting vitamin C, which is justified, since a single navel orange provides almost all of your daily requirement of the vitamin, but they’re also incredibly low-calorie. This is particularly true of grapefruit; that telltale sour grapefruit taste is because the fruit has less natural sugar than its sweeter cousins. Eating a fresh grapefruit every day has also been linked to weight loss and lower cholesterol.
However, if you just can’t stand the sour taste of grapefruit without throwing on tons of sugar or other sweeteners, oranges and tangerines can make viable substitutes. A 2005 study showed that participants’ body mass index was inversely related to vitamin C consumption – essentially, the more vitamin C you eat, the lower your BMI. This may be because vitamin C affects the way that your body burns fat. Either way, it suggests that eating citrus fruit is a terrific way to keep off the pounds.
Each strawberry you eat only gives you four calories, but it gives you so much more in terms of nutrition. In addition to being full of potassium and vitamin C (eight strawberries have more vitamin C than an orange, they’re high in potent antioxidants called polyphenyls, which are particularly good at fighting off cancer and heart disease.