Debunking 'Negative Calorie' Foods

 

 

Q: What do the above foods all have in common?

A: They are often touted as the poster children for 'negative calorie' foods.

Definition:

A negative calorie foods is a popular term used within the diet and fitspo blogosphere to describe foods which are believed to require more energy to digest than they provide. The theoretical net result is a caloric deficit which is oft hailed as a 'diet & weight loss secret'.

Debunking the Myth:

The idea of negative calorie foods sounds amazingly convenient - we can eat an unlimited amount of the above foods which will pave a guilt-free path to skinniness that we all desire. That ... plus, it sounds 'legit'.

Unfortunately, when we shine the light of evidence-based practice upon this assertion, the testable truth sounds somewhat less sexy than the miraculous claim.

To understand the fallacy of 'negative calorie' foods, we must first understand the thermic effect that food has within the body. The thermic effect of food is, essentially, the caloric 'cost' of digesting it. It is also the reason why negative calorie foods, by simple explanation, cannot burn more calories than they contain. If we examine the thermic effect of different nutrients we see that the magnitude depends on the composition of the food consumed:

Carbohydrates: 5 to 15% of energy consumed
Fat: 5 to 15% of energy consumed
Protein: 20 to 35% of energy consumed

To burn more calories than it contains, an item would be required to have a thermic effect of greater than 100%. Unfortunately, even proteins, which require the most energy to digest, only burn anywhere between 20 - 35% of the energy contained.

What about Bioactives, etc?

Though there is a possibility that there could be bioactive compounds in certain foods which increase metabolic rate, this would depend on ingestion of certain foods (e.g. grapefruit) and would not apply to all 'negative calorie' foods.

Your best bet would appear to be to pepper your food with chilli or MCT (e.g. coconut oil), which has been shown to increase diet induced thermogenesis by over 50%. But, even then, your negative calorie foods would fall short of their 100% target.

Bottom Line: Who Cares Anyway?

Assuming that a kilogram of fat requires a caloric deficit of 3,500 calories to burn, 10 calories of celery here (even if it were negative calorie), would not produce significant effects to any dieter's weight loss goals.This is especially so in our contemporary world, built so heavily around the instant gratification of desire.

A better strategy for any dieter would be to focus on appropriate macro-nutrient intake, particularly increasing protein to adequate amounts. This, in combination with the insulin sensitizing effects of a lower carb / high fat diet as well as high intensity training will produce measurable and visible effects that you can bank on.

Unfortunately, negative calorie foods are no 'magic bullet' for those seeking weight loss. However, they do tend to provide higher water and fiber content which can assist with improving satiety and controlling hunger. This, in itself, can be a benefit in the battle of the bulge.

Reference:

Clegg, M. E., Golsorkhi, M., & Henry, C. J. (2012). Combined MCT and chilli feeding increases diet induced thermogenesis in normal-weight humans. European Journal of Nutrition, 52(6), 1579-1585.

Shepphird, S. F. (2009). Question 74: 100 Questions and Answers about Anoerxia Nervosa. Jones & Bartlett, p. 171.