Dr. Tim Says....

The Negative Calorie Diet

One of the most amazing "diets" that I have come across recently is the "Negative Calorie" diet.

There has long been a theory that some low calorie foods actually burn more calories during digestion than that particular food contains. A bit silly, I know, but there are actually books written about this.

The basis for the concept is the "thermic effect of feeding." This is the scientific phrase used to describe the calories used in digesting foods. It has been shown that in a routine day we use about 10% of the calories we take in for digestion. For instance, in a typical 400 calorie meal the body will use about 40 calories for digestion and absorption of the nutrients. (We know that proteins use a little more energy than fats or carbohydrates.)

Negative calorie meals seem like a great idea but the amount of foods needed to actually cause weight loss would be much more than one would ever want to eat. If you consider the average meal taking 40 - 50 calories to consume, then a really large bowl of lettuce might just burn more calories than are in the greens.

The list of foods below shows the number of calories in the foods commonly thought of as "negative calorie."

Food	Portion	Calories
Celery	1medium stalk	6
Oranges	1 cup sections	81
Strawberries	1 cup halves	49
Tangerines	1 cup sections	103
Grapefruit	1 cup sections	74
Carrots	1 cup chopped	52
Apricots	1 cup halves	74
Lettuce	1 cup shredded	5
Tomatoes	1 large	33
Cucumbers	1 cup slices	16
Watermelon	1 cup balls	46
Cauliflower	1 cup	25
Apples	1 cup chopped	65
Hot chili peppers	1 pepper	4
Zucchini	1 cup chopped	20

All of the foods on the list are really healthy, but adding up a salad with a cup of lettuce and half cup of cucumbers, cauliflower, carrots and zucchini along with a tomato and a stalk of celery yields 105 calories. Note that this is before adding any salad dressing. Assuming that one would burn the full 40 calories from any meal, the theory still fails.

105 calories consumed - 40 calories burned in digestion = 65 positive calories.

The foods that are on many "negative calorie" lists are - for the most part - fresh foods that are great tasting and great for you. It’s easy to lose weight by simply substituting these for what most folks eat today in processed, pre-packaged foods which is why the authors of such books are successful.

The key is caloric density. Those foods on "negative calorie" lists are not calorie dense. While a cup of carrots has 52 calories, a cup of low-fat cottage cheese contains 163 calories and a cup of Ben and Jerry’s Chocolate Chip Cookie Dough ice cream comes in at 540 calories. (Interestingly, the body uses some calories to warm up that ice cream -- maybe about 7 - 10.)

It would be great to have detailed research on each of these ingredients that told us exactly how the body handles a particular food. We quite simply don’t have that degree of information to make any claim that they burn more calories in digestion than they contain.

One food on the list that has long been thought of as "negative calorie" is hot chili peppers. This is another myth that has been recently debunked in a very elegantly designed study that I wrote about in a News Bite back in April.

Remember, if something seems too good to be true, then it probably isn’t, and a silly diet based on "negative calories" is certainly too good to be true.

Eat well, eat healthy, enjoy life!

Dr. Gourmet
March 31, 2008

Last updated: 03/31/08