Negative Calorie Foods

Time had an article on line about 10 dieting myths. One of them is "There are no negative calorie foods." On the one hand, this is true, on the other they are full of shit. There are lots of foods (mostly vegetables, but some fruit) that contain very little in calorie content, while they have lots of fiber, and are generally harder to digest. I have seen widely varied information on calorie content vs. available calorie content and different values for burned and "stolen" calories (fiber has a tendency to extract calories in the form of fat from our bodies, mostly in the digestive tract but soluble fiber can clean up some of the fat in our arteries, particularly those in LDLs.

In the end if you eat something that has nearly zero available calories (lettuce, celery), then even the very small amount of calories you must burn to consume them make them negative calories. Depending on the timing, the ability of fiber to bind fat in our digestive tract means that high fiber foods can remove calories contained in high fat foods by keeping them from ever being absorbed by the body.

Quantifying becomes very difficult. Even if you can do all the different equilibrium calculations necessary, the relative concentrations are dependent on what you eat, when you eat it, and your specific metabolism. The exact amount of "negative calorie" intake you can really get in a day is very difficult due to the fat robbing issue--maximized by eating too much fat anyway--but you can eat foods that will reduce your total calorie count for the day. Of course, you won't know by how much, and it isn't like a carrot is going to cancel that slice of pizza.

In the end it is a bad idea to depend on or try and count negative calories, but it is a very good idea to eat fruit and veggies. On their own is all good, but the complimentary benefits of filling your stomach and having some of that fiber peel off a bit of the other fat you've consumed, means that the best use of veggies is as a substantial (by volume or weight) fraction of a meal. You will eat less of the high calorie (meat and carb) portions as a result.