Are There Really any ‘Negative-Calorie’ Foods?

Most people know to consider their calorie intake when trying to lose or gain weight. Calories are a measure of the energy stored in foods or in the tissues of your body.

Typical recommendations for weight loss focus on eating fewer calories or using more of your stored calories through physical activity. Some foods have become popular in weight loss diets because they’re supposedly “negative-calorie,” meaning that you lose calories by eating them.

Here’s what you need to know about negative-calorie foods, including whether they can help you lose weight.

WHAT ARE NEGATIVE-CALORIE FOODS?

Food provides your body with a variety of nutrients, including three main categories that dole out energy in the form of calories: carbs, fats and proteins. Your body has to expend energy in order to digest and process any food you eat. The amount of energy required varies based on the food (1).

The term negative-calorie food typically refers to a food which supposedly takes more calories to eat, digest and process than it naturally contains and gives to your body. If these foods exist, you could theoretically lose weight by eating them, as you would use more calories eating and digesting them than you gain from their calorie content.

Common Foods

Foods promoted as negative-calorie are typically fruits and vegetables with high water content. Some specific examples include: 

• Celery: 14 calories per cup (100 grams), 95 percent water (2)
• Carrots: 52 calories per cup (130 grams), 88 percent water (3)
• Lettuce: 5 calories per cup (35 grams), 95 percent water (4)
• Broccoli: 31 calories per cup (90 grams), 89 percent water (5)
• Grapefruit: 69 calories per cup (230 grams), 92 percent water (6)
• Tomatoes: 32 calories per cup (180 grams), 94 percent water (7)
• Cucumbers: 8 calories per cup (50 grams), 95 percent water (8)
• Watermelon: 46 calories per cup (150 grams), 91 percent water (9)
• Apples: 53 calories per cup (110 grams), 86 percent water (10)

Other similar fruits and vegetables, such as lemons, cabbages, berries or zucchini, are commonly included in these lists as well. Since each of these foods contains calories, the question is whether or not your body uses more calories to process these foods than the foods contain.

THERE ARE NO ACTUAL NEGATIVE-CALORIE FOODS

Though it’s true that most of these foods are nutritious, it’s unlikely that any of them are negative-calorie. Each of them contains calories, and there is no evidence to support the notion that they require more energy to eat, digest and process than they provide.

Calories Used to Chew Food

Some people wonder if the energy expended during chewing could help contribute to a food being negative-calorie. A limited amount of research has shown that chewing gum increases the energy your body uses by about 11 calories per hour (11).

Therefore, the amount of energy you use during a few minutes of chewing celery or other foods is probably very small and relatively unimportant.

Calories Used to Digest Food

While it’s true that your body uses calories to process foods, the number of calories used is less than the calories foods provide (12).

In fact, the amount of energy your body uses to process foods is usually described as a percentage of the calories you eat and is estimated separately for carbs, fats and proteins. For example, the energy used to process foods is about 5–10 percent of the calories the food contains for carbs, 0–5 percent for fat and 20–30 percent for protein (1).

Most alleged negative-calorie foods are composed primarily of water and carbs, with very little fat or protein. It’s unlikely that the energy used to digest these foods is dramatically higher than for other carb-based foods, though this has not been studied specifically.

What About Zero-Calorie Items?

Similar to negative-calorie foods, zero-calorie items — such as cold water — are often promoted as increasing metabolism.

Some research does support small increases in metabolism for a short period of time after drinking cold water. However, the size of the increase is small, ranging from about 3–24 calories over the course of one hour (13, 14, 15).

Similar to chewing, drinking cold water does expend some calories. However, such small effects will not substantially increase the calories your body burns.

THERE ARE PLENTY OF NUTRIENT-RICH AND LOW-CALORIE FOODS

Even though negative-calorie foods probably don’t exist, many of the foods commonly promoted as negative-calorie are still very nutritious. What’s more, due to their low calorie and high water contents, you can often eat a fairly large volume of these foods without consuming too many calories.

In addition to the foods listed earlier in this article, here are a few other fruits and vegetables that are rich in nutrients but low in calories:

• Kale: Contains only 7 calories per cup (20 grams), but is packed with vitamins A, K and C, as well as several minerals (16, 17).
• Blueberries: Contain 84 calories per cup (150 grams) and are a good source of vitamins C and K, as well as the mineral manganese (18).
• Potatoes: Contain 58 calories per cup (75 grams) and are good sources of potassium and vitamins B6 and C (19, 20).
• Raspberries: Contain 64 calories per cup (125 grams) and are good sources of vitamin C and manganese (21).
• Spinach: Like kale, contains only 7 calories per cup (30 grams) along with vitamins K and A, as well as several other vitamins and minerals (22).

A diet that includes a variety of nutrient-rich whole foods is beneficial for weight loss and overall health (29, 30).

There are several advantages to whole foods over processed foods. Whole foods often contain a greater variety of vitamins, minerals and other beneficial compounds than processed foods (29). These foods may ultimately help you live a longer, healthier life (31, 32). Additionally, your body may, in fact, use more calories digesting whole foods than processed foods.

One study found that 20 percent of the calories in a whole-foods meal were used to digest and process that meal, compared to only 10 percent for a processed meal (33). Importantly, focusing on a select list of alleged negative-calorie foods may cause you to miss out on many other foods that provide you with important nutrients.

For example, the foods on negative-calorie lists often contain no protein or fat, both of which are vital for your wellbeing. What’s more, the specific foods listed in this article only represent a slice of the delicious, low-calorie whole foods you can enjoy as part of a well-rounded diet.

THE BOTTOM LINE

Negative-calorie foods allegedly take more calories to eat, digest and process than they provide to your body. They’re typically low-calorie vegetables and fruits with a high water content.

However, it’s unlikely that any of these foods are truly negative-calorie, though they can be part of a nutritious, healthy diet. Rather than focusing on specific foods that supposedly trick your body into burning more calories than it consumes, aim instead to enjoy a variety of nutritious foods.