Is A Calorie Just A Calorie?

I just want to call your attention to an interesting article and accompanying editorial that was published in JAMA last week (volume 24, July, 27, 2012).  The original article was entitled, “Effects of dietary composition on energy expenditure during weight-loss maintenance,” and written by CB Ebbeling et al (senior author was DS Ludwig) from Harvard University.  The accompanying editorial was entitled, “Diet and exercise for weight loss,” and written by GA Bray.  In addition, there was an opinion piece in the NYT that summarized the article and the editorial ( Sunday, July 1, 2010, page 5 of the  Sunday Review section, “What really makes us fat,” written by G Taubes).

The study design

The investigators asked the following question: does diet composition matter in manitenance of weight loss or is it just calories?  The study took 4 years (06/2006-06/2010) and included 21 adults ages 18-40 years (17 females and 15 males) with BMIs 27 or greater.  During a run-in period, study subjects were put on diet plans that resulted in an average weight loss of 14.3 kg or 13.6% of the initial body weight.  Then study subjects were randomly rotated through 3 diet plans, each for one month.  The diet plans were very low fat (basically an Adkin’s type diet), low glycemic index, and high carbohydrate.  Each study subject was provided calories equal to his or her  caloric expenditure which was determined by a very fancy method I didn’t really understand.  So the idea was to find out if a study subject’s caloric expenditure differed among the three diet plans.  The investigators found that caloric expenditure was greatest on the very low carbohydrate diet and lowest on the high carbohydrate plan; the difference was about 300 calories/day, which is a big deal (the difference was about 150 calories in relation to the low glycemic index diet).  The investigators concluded that diet matters and that a calorie is not just a calorie if one takes into account differences in energy expenditure related to the calorie composition.

What about the editorial?

The editorial was written by George Bray, a highly respected investigator.  Dr. Bray felt the study was well designed but that it was risky to jump to conclusions about effects of differences in diet composition on long-term weight loss success.  He also noted that it is already well known that protein is a potent stimulator of energy expenditure and that the very low carbohydrate diet had about 10% more protein than the other diets.  Dr. Bray concluded his editorial by saying that caloric restriction is much more important than diet composition in effecting long-term weight loss.

What does it all mean?

I will not offer any personal opinion regarding the clinical significance of the study results published by Ebbeling and colleagues other than to say that the study results are interesting.  I think I can say without fear of being incorrect that most obesity in the U.S. has a strong genetic basis with too many calories in and too little energy expenditure.  I don’t care how much protein one takes in, it won’t be enough to overcome the intake excess and the lack of energy expenditure the old fashioned way- exercise, etc.   I am curious why it took 4 years to complete the study which included only 21 subjects.  I almost forgot to mention that the investigators did  find some troubling things with the very low carbohydrate diet (aka high protein, high fat diet)- high serum cortisol levels and increased levels of blood inflammatory factors.  Who knows what this means?   If you are interested in this stuff, I urge you to read the NYT piece written by Mr. Taubes.  I must warn you that he may not have been the best choice to review the Ebbeling et al study since he has made clear from his previous writings that he would be less cautious than Dr. Bray in embracing the study results.  Mr. Taubes has written extensively on obesity.  He has a best-seller from 2010 entitled, “Why we get fat: and what to do about it,” and an earlier book (2007) entitled, “Good calories, bad calories: challenging the conventional wisdom on diet, weight control, and disease.”  The same book was published in the UK entitled, The diet delusion.”  If you want even more, you can check out Mr. Taubes’s website (GaryTaubes.com) or his wikipedia entry.  Happy eating.

Just one more thing

This has nothing to do with the discussion above, for those of you who are interested in childhood obesity (I hope all of us), there is an interesting infographic that you should know about.  Its title is “America’s fat future.”  Check it out.

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