Friday, February 09, 2007

Adaptive Thermogenesis Can Impede Weight Loss

A calorie is a calorie is a calorie; so we're told.

Calories in - calories out matter when it comes to our weight; so we're told.

Eat less and move more, reduce calories and increase calories used, the secret to weight loss; so we're told.

Back in 2004, Drs. Feinman and Fine offered up a paper, published in Nutrition & Metabolism, "A calorie is a calorie" violates the second law of thermodynamics.

Within that paper, it was noted that, "A review of simple thermodynamic principles shows that weight change on isocaloric diets is not expected to be independent of path (metabolism of macronutrients) and indeed such a general principle would be a violation of the second law. Homeostatic mechanisms are able to insure that, a good deal of the time, weight does not fluctuate much with changes in diet – this might be said to be the true "miraculous metabolic effect" – but it is subject to many exceptions. The idea that this is theoretically required in all cases is mistakenly based on equilibrium, reversible conditions that do not hold for living organisms and an insufficient appreciation of the second law. The second law of thermodynamics says that variation of efficiency for different metabolic pathways is to be expected. Thus, ironically the dictum that a "calorie is a calorie" violates the second law of thermodynamics, as a matter of principle."

While the paper has been cited a number of times over the years, no other major study or paper has challenged the idea that weight loss is mostly dependent on "calories in calories out" - so lacking is any question of this belief that many continue to hold the not-so-subtle idea that if someone isn't losing weight on a calorie restricted diet, then they are not restricting calories enough or they're cheating and just won't admit it.

Well folks, get ready to read an eye-popping study published this month in the International Journal of Obesity, Clinical significance of adaptive thermogenesis. (full text)

The conclusion?

In conclusion, based on studies that have shown a greater than predicted decrease in EE under energy restriction circumstances, this review presented arguments in support of the potential of adaptive thermogenesis to impede obesity treatment on a short- and long-term basis, at least in some individuals. In some cases, the adaptive decrease in thermogenesis was shown to be significantly related to a single cycle of body weight loss and regain, an increase in plasma organochlorine concentration following weight loss, and a lower than predicted EE was also shown to be associated with severe nocturnal oxygen desaturations in OSAS. This suggests that energy metabolism might be sensitive to stimuli of different physiological nature and that adaptive thermogenesis could be quantitatively more important than what is generally perceived by health professionals and nutrition specialists. However, from a clinical point of view, several issues remain to be investigated in order to more clearly identify adaptive thermogenesis determining factors and to develop strategies to cope with them. Along these lines, it is concluded that unsuccessful weight loss interventions and reduced body weight maintenance could be partly due, in some vulnerable individuals, to the adaptive thermogenesis, which is multicausal, quantitatively significant, and has the capacity to compensate for a given prescribed energy deficit, possibly going beyond any good compliance of some patients. [emphasis mine]

Weight loss impeded, even with restricting calories and good compliance?

Who'da thunk it possible?


  1. Great find Regina!

    I will have to check it out, I have been waiting to see something like this on paper.

  2. Anonymous5:56 AM

    Numbers, please. Lots of multisyllabic words there. But "impede" = what percent? According to the researchers, metabolism is more efficient by 0.1%? 1%? 10%? 50%? Calories to maintain in an "impeded" individual less by 5? 25? 50? 100? 500? 2000? Let's see some quantification.

    The general conclusions of this paper are not new, if all it's saying is that metabolism varies up to about +/-5% over the population. If it's saying something else, like +/-50%, that would be news.

    A five percent variation for a 2,000 calorie diet is 100 calories. So an "impeded" person would be "doomed" to eating 100 calories fewer per day to maintain her weight. This is not something that can realistically used as an excuse for being fat. And this is at the far end of the variation, applicable to few people.

  3. It still comes down to "calories in, calories out." It's just that the "calories out" goes down in some people.

  4. Lady Atkins - Yeah, probably closer to the 50% down (maybe even 75% down?) in some people, which means it doesn't fit the standard calories in, calories out "rule" of eat X number of calories, based on current weight + Y calories based on exercise type and time, and expect to lose Z amount per week, as if it's a tried and true formula. Just doesn't work like that for people whose bodies have adapted so well to using far fewer calories than the numbers claim they should be expending.

    Then there's the thing of what kind of calories they are, because you and I both know that if we ate anywhere near the same number of calories exclusively from carbs as we do from our low-carb diets, we'd balloon up mighty fast.

  5. I do know that in every weight loss study that I've examined, there was less weight loss than the calories restricted, somewhere between 50 and 75%. The calories in and out theory also doesn't work by analogy. Try putting diesel fuel in your gas powered car. It wouldn't run or, at best, run badly before it died. Since cars with diesel engines get better milage, it's not the energy content. Same thing applied to octane ratings in gasoline which describes how easily the gasoline ignites. If I try running my super turbo hot rod for which premium is recommended on 86 octane, it will run poorly, knocking badly, if at all even though the energy content of regular and premium gas is the same.

  6. Something to keep in mind is the state of your muscles, since muscle is a big driver of metabolism. Going on a crash diet can both lower your metabolism in reaction and also eat up muscle. And inactive people over 30 can lose a pound of muscle a year, further killing the metabolism..

    I'd think that doing some strength training to increase or at least keep the current level of muscle would do a lot to help most people accomplish weight loss...

  7. Anonymous8:28 PM

    Many low-carbers have verified that strength/weight training greatly increases weight loss.

  8. Anonymous10:51 AM

    Why do people keep trying to find more excuses for people to latch on to? The fact is, most people do not get into a consistent routine of diet and excercise, and they want to point to some limiting factor that does not apply to the vast majority. Stop misleading and get people to do diet the right way. Eat right, excercise, and for the people that do it right and can't lose weight, find out if they have a thyroid problem or something else that truly is impeding them.

  9. Anonymous6:11 AM

    Very Interesting!
    Thank You!