Do negative calorie foods really exist?

Calories are the measure of energy an item of food provides. When a person exercises, the body uses calories that a person has taken in through their diet as fuel. The body also uses calories to carry out essential functions, such as digestion, pumping blood, and breathing.

When a person consumes more calories than they use through physical activity or normal body functions, the body stores the calories as fat.

A negative calorie food would require the body to use up more calories digesting the food than it would contain.

As a result, a person could theoretically lose weight by eating negative calorie foods, if doing so helped them create a calorie deficit.

This article discusses the evidence regarding negative calorie foods and the benefits and dangers of pursuing a diet touted as “negative calorie. 

According to the Academy of Nutrition and Dietetics, a person’s body burns approximately 10% of their daily calories through thermogenesis, which includes chewing and digesting food and storing its nutrients.

Different nutrients use up different amounts of calories, according to an older, 2004 study into diet and thermogenesis. 

The percentage of calories burned during thermogenesis for each nutrient is:

• Fat: 0-3%

• Carbohydrate: 5-10%

• Protein: 20-30%

• Alcohol: 10-30%

This study also showed that the body burns calories from food for up to 6 hours after a person eats.

The amount of calories a person burns while they rest depends on their age, height, weight, and body composition – for example, how much muscle they have.

Chewing gum

A small 2015 study involving 17 men and 13 women concluded that participants who chewed gum after a meal burned 3–5%  more calories than those who did not chew gum after eating.

However, another method of burning extra calories after a meal is to eat more slowly, which a 2016 study found had the same effect as chewing gum.

Celery

Celery is commonly advertised as a negative calorie food because it has high water and fiber content.

However, a 2019 study, which is not yet peer-reviewed, concluded that celery is not a negative calorie food.

The study found that lizards that ate celery used 33% of the calories in the meal for digestion, while 43% of calories were lost through faeces and urine.

The lizards absorbed approximately 24% of the calories from the celery they ate.

High water content foods

The foods that many people believe to be “negative calorie” are fruits and vegetables that have a high water content.

Some of these hydrating foods include:

• Watermelon: 91.45 grams (g) per 100 g

• Grapefruit: 88.06 g per 100 g

• Tomatoes: 94.52 g per 100 g

• Carrots: 88.29 g per 100 g

• Cucumber: 95.23 g per 100 g

• Lettuce: 95.31 g per 100 g

• Celery: 95.43 g per 100 g

Dangers of a low calorie diet

Eating a very low calorie diet may mean a person does not meet their nutritional needs. The 2015-2020 Dietary Guidelines for Americans states that intake of fruit and vegetables is below the recommended amounts across all age and sex groups.

It also lists the following nutrients that the population is not consuming enough of:

• potassium

• dietary fiber

• choline

• magnesium

• calcium

• vitamins A, D, E, and C

• iron

Although eating a diet rich in fruit and vegetables will provide a person with these nutrients, eating a low calorie diet may slow down a person’s metabolism, leading to their body using muscle for energy, according to a 2014 study. Low calorie diets that do not contain enough carbohydrates may also cause fatigue, according to a 2007 study. According to the Academy of Nutrition and Dietetics, low calorie diets may also lead to gallstones.

Low calorie, high nutrient foods

There are a wide range of foods that are very nutritious and contain a low number of calories proportionate to their volume.

Apples

One small apple can contain as few as 86 calories. Apples are a great source of vitamin C, calcium, phosphorus, and potassium.

Grapefruits

A 25 g slice of grapefruit contains 10.5 calories. Grapefruit is also rich in magnesium, potassium, and vitamin C.

Strawberries

One cup of strawberries offers 48 calories. Strawberries are a good source of potassium, vitamin C, magnesium, and calcium.

Apricots

Apricots are a rich source of calcium, phosphorus, and magnesium, and only contain 74 calories per cup.

Peppers

One regular sized raw pepper contains. The calcium, potassium, and folate content is also high in peppers, along with vitamin C.

Tomatoes

One raw Italian tomato contains 10.8 calories, while a cherry tomato contains just 4 calories. The nutritional content of tomatoes include high amounts of potassium, vitamin C, and phosphorus.

Beets

A single raw beet contains 34 calories. Beets also have a high amount of potassium, magnesium, and folate.

Radishes

One radish contains less than 1 calorie. 100 g of radishes contains only 16 calories, as well as high levels of vitamin C, folate, and potassium.

Pumpkin

Cooked pumpkin contains 51 calories per 100 g. Magnesium, phosphorus, potassium, and folate are all found in good amounts in pumpkin, too.

Green beans

100 g of raw green beans offers 31 calories. Green beans are a source of calcium, magnesium, potassium, and folate.

Plain Greek yogurt

A 100 g portion of plain, non-fat Greek yogurt contains 61 calories and offers 10.3 g of protein. Plain Greek yogurt is also a good source of calcium, potassium, and phosphorus.

Eggs

One large egg contains 72 calories. There are 6.24 g of protein in every egg, as well as high amounts of folate, calcium, and potassium.