Some foods have a negative calorie effect.
WHAT THEY’RE SAYING
It’s claimed that some foods [celery, cucumbers, cabbage and grapefruit are most commonly mentioned] have a "negative calorie effect," meaning that the act of chewing and digesting these foods burns up more calories than the food itself contains.
WHAT WE KNOW
While it may seem as if chewing expends a lot of energy, especially for foods that require a lot of chewing, in reality, chewing uses only about 11 calories per hour no matter what type of food is being chewed. It does indeed take calories to digest food. However, the amount of calories expended to digest food only accounts for 5-10% of the total calories that you eat and varies from individual to individual and how much is eaten at any given time. A few more calories are expended when digesting protein and carbohydrates than when digesting fat. This difference between fat, carbohydrates and protein is minimal, however, in the grand scheme of total daily calories consumed vs. calories expended.
So the bottom line is that low-calorie, high-nutrient foods will certainly help a person to lose weight, not because they create negative calories, but because they are being eaten instead of crackers, chips, sugar-sweetened beverages, cookies or other high-calorie foods, low-nutrient foods.
HOW DO WE KNOW THIS?
The Celery Scenario
Two medium stalks of celery contain around 15 calories. Eating two medium stalks of raw celery takes about four minutes. This means someone could eat about 15 two-stalk servings in an hour for a total of 225 calories. Chewing the celery for one hour would burn 11 calories. Since it takes 5-10 percent of calories consumed to digest food, it would take about 10-20 calories to digest 225 calories worth of celery. So the act of eating 15 two-stalk servings of celery (for a total of 225 calories) would burn about 20-30 calories (both chewing and digesting). As you can see, this is not “negative calories.”
The Harris-Benedict Equation, commonly used in clinical practice, can help you determine your caloric needs. MyPyramid.gov can also offer a glimpse of your caloric needs.
Eating fruits and veggies matters when trying to lose weight or to maintain a healthy weight and also may reduce the risk of many diseases. However, eating a colorful variety of fruits and vegetables, not just large amounts of a limited variety, is the best way to provide a wide range of valuable nutrients like fiber, vitamins and minerals.
Studies have shown that those who consume more fruits and vegetables while decreasing the amount of fat and added sugar they consume manage their weight better, are less hungry, and have a better intake of healthy nutrients. Fruits and vegetables help with managing weight because most are lower in calories and their high water and fiber content leads to a feeling of fullness, which helps a person eat less.
If you’re looking to lose weight, your best option is to replace less healthy foods in your diet with extra fruits and vegetables. Here are some examples: replace half your usual portion of protein with extra vegetables and make sure the protein you do eat is lean, have fruit instead of a pastry or candy dessert, and make sure you get plenty of physical activity. Research has shown that physical activity helps a person lose weight and keep it off, not only because of the calories expended during exercise, but because exercise helps build muscle, which burns more calories when resting .