This isn't concrete scientific fact just yet, but many studies have been done on this topic, and an explanation for why some foods may be considered negative calorie is as follows. Once again, nearly all foods have calories. And while no foods actually contain actual digestive enzymes, higher quality whole foods (read: non-processed) have vitamins in them. What some of these vitamins do is trigger the release of digestive enzymes to break down the food we've just eaten.
When we eat junk food, this same process happens. The difference is, there are no enzyme triggering vitamins in junk food. So there's a minimal release of enzymes, then the rest of the food is left to be taken up as fat or secreted as waste. HOWEVER, in the so called "negative calorie foods," the enzyme release is enough to break down the food and leave a surplus of enzymes. Where the debate lies is in this. It is not entirely known if the excess enzymes make their way into the blood stream. If they do, enzymes are responsible for accelerating the metabolism, therefore increasing the likelihood of fat loss.
While not conclusive, there has been some fascinating research done lately that looks promising.
"According to a recent study performed by Dr. Dean Ornish, M.D., of the University of California, at San Francisco, a vegetarian diet consisting mostly of fruits and vegetables, was adhered to by research subjects as an experimental study on the reversal of heart disease. As a result each of the research subjects (all suffering from heart disease), lost an average of 20 pounds without cutting calories or limiting serving sizes.
In light of the fact that these subjects were 40 years and older (with relatively slowed metabolisms) and the research performed involved no prescribed exercise program, this constitutes a dramatic weight loss that could only be attributed to the consumption of various fruits & vegetables."
So could it be that easy? Eat high quality, non-processed foods along with "negative calorie" fruits and vegetables and experience considerable fat loss? It very well could be. Regardless, a diet consisting of high quality proteins, vegetables and fruits will make you healthier. So essentially you have nothing to lose. Oh, and I suppose I should give you a small list of some of these negative calorie foods before you get mad for sticking in there so long. Keep in mind, these foods should be eaten raw or lightly cooked. Overcooking any produce can result in nutrient loss. These are just some of the foods that were given to the people in the study:
- Vegetables: sweet potatoes, celery, eggplant, all types of peppers, artichokes, parsley, leeks, spinach, different types of lettuce, carrots, asparagus (cooked), radishes and broccoli (raw).
- Fruits: pears, strawberries, raspberries, cantaloupe, plums, oranges, grapefruit, blackberries, blueberries, watermelon, lemons, limes and pineapple.
- Bonus item- Seafood: tuna, flounder, sea bass, trout, cod, lobster, crab, clams, mussels, crayfish, oysters, prawns and shrimp.
Try adding some of these into your diet, along with other healthy foods and see how it affects your overall body composition in conjunction with physical activity. You might just be surprised at what happens! Everyone have a great day, eat your fruits and vegetables, and go work out!