Friday, February 5, 2010

Challenging Conventional Interpretation of the Law of Conservation of Energy

In the last few postings I asked a couple questions regarding obesity and dieting. Essentially, we acknowledge that Americans are getting fatter each decade and when they care enough to intervene with a diet and/or exercise program the failure rate is extremely high. The common answers are that people eat too much and move too little, therefore causing weight gain. Then, they start dieting and get frustrated with a lack of results or a plateau. Another year, the same wisdom is thrown around.

On the surface, this conventional thinking seems logical: eat more and move less, and you will get fat. Just about everyone believes this conventional wisdom and do not question it. Heck, even The Biggest Loser, Oprah, and several medical 'experts' purport the generic advice to eat less and move more.
It all goes back to the application of the Law of Conservation of Energy: energy can not be created or destroyed, only converted from one form to another.
After Max Rubner, a German chemist, discovered the energy equivalent of fats, carbohydrates, and protein in 1900, the Law of Energy Conservation has been applied to human nutrition. It is known today as a 'Calorie is a Calorie'.
Nutritionists insist that you can not violate the Law of Conservation of Energy. And this became their basis for advising low-fat and low-Calorie diets. "Eat less Calories and you will not gain weight."
"Add a few thousand more steps in your day and you will lose a few pounds over a couple weeks." Most people would agree with these statements. This interpretation of the Law of Conservation of Energy is the cornerstone of almost all weight-loss programs.
The problem is, it is flawed. This interpretation is not supported by obesity research. But, it continues to be the basis for all obesity research and public health intervention. Why is obesity such a problem? One big reason why people don't succeed at weight loss (or are gaining more and more weight), I believe, is that we have misinterpreted the Law of Conservation of Energy applied to human physiology. Why? Well, like most ideas in science, it can get a bit complex. It is easier to learn something that is very straight-forward (but, not correct).
I have Gary Taubes to thank and his book: Good Calories Bad Calories, where he challenges the conventional wisdom of the 'science' of diet and health.

In this book, he challenges the conventional interpretation of the Law of Conservation of energy and offers an alternative hypothesis.

It comes down to, like a lot of problems in science, infering causation (i.e. something causes something else) when we have an association. Before we get into breaking this misinterpretation down, here is an example. My seven-year old son eats a lot of food. He has grown a couple inches over the last six months. All of that food he has eaten must have caused him to grow that much. If I eat more food, I will grow a couple of inches.
Obviously, in this example, my logic is flawed. The association of high levels of food consumption is associated with my son's growth, but I can't infer from these observations that the high levels of food consumption caused him to grow. It is pretty evident if I test it on myself.

In the next post we will break-down the Law of Conservation of energy and test it's association for causation. And, you thought you would never use statistics again in your life!


David Brown said...

The "calorie is a calorie" argument ignores the role of gut microbiota in energy apportionment. I think the evidence indicates that a substantial portion of what we consume gets metabolized by the approximately 2 kg of gut microbes that inhabit our digestive tracts.

To account for all energy consumed, scientists need to determine the amount of heat energy generated per gram of dry fecal gut microbiota. Researchers have estimated that 30 to 50 percent (or more) of dry fecal matter consists of gut microbes. To my knowledge, the heat generated by the various sorts of gut microbiota, both aerobic and anaerobic has never been factored into the energy balance equation: Calories in = calories stored + calories out. The calories out portion of the equation consists of energy absorbed into the bloodstream and metabolized by the body as well as energy metabolized by gut microbiota as they multiply. Since heat produced by gut microbiota diffuses into the body as it is generated, a scientist utilizing a metabolic chamber to determine basal metabolic rate would not be able to distinguish gut microbiota-generated heat from heat generated by the body's own metabolism. Moreover, scientists measuring the fat content of fecal matter routinely conclude that 98% of fat consumed gets absorbed into the bloodstream. But gut microbiota utilize fat calories also. Consequently, waste products generated by gut microbiota fat metabolism would not register as fat calories in the feces.

Gut microbes can also modulate the rate at which calories get absorbed into the bloodstream. Google "WASTE FROM GUT BACTERIA HELPS HOST CONTROL WEIGHT, RESEARCHERS REPORT" to access an article with the below quote:

"In both cases, the mice weighed less and had a leaner build than their normal counterparts even though they all ate the same amount."

Interestingly, both Taubes and Bray didn't think gut microbes could possibly have a significant effect on the amount of energy absorbed into the bloodstream.

Dan Hubbard, M.Ed. said...

David: Thanks for adding support to the arguement that a Calories in=Calories out hypothesis is flawed. You opened up a whole other can of worms with the tremendous variability of gut bacteria and their symbiotic role in energy regulation of our bodies. We must factor in their usage of Calories, but also how they influence our digestive physiology (intestine transit time) and our hormonal control of energy intake (Leptin, Ghrelin). Interesting stuff and much more complex than we have given the body credit for being. Additionally, raises even more concern about common antibiotic use and keeping kids in a "sterile environment."