Wednesday, June 27, 2012

An Interesting Study Was Just Released

You can read much of a recent study published in JAMA in the following link:

Effects of Dietary Composition on Energy Expenditure During Weight-Loss Maintenance

In the study, scientists measured the effects of three maintenance diets, very low carb, low fat, and low glycemic index.

Here are some interesting quotes from the study:
The results of our study challenge the notion that a calorie is a calorie from a metabolic perspective. During isocaloric feeding following weight loss, REE (resting energy expenditure) was 67 kcal/d higher with the very low-carbohydrate diet compared with the low-fat diet. TEE (total energy expenditure) differed by approximately 300 kcal/d between these 2 diets, an effect corresponding with the amount of energy typically expended in 1 hour of moderate-intensity physical activity.
 Although the very low-carbohydrate diet produced the greatest improvements in most metabolic syndrome components examined herein, we identified 2 potentially deleterious effects of this diet. Twenty-four hour urinary cortisol excretion, a hormonal measure of stress, was highest with the very low-carbohydrate diet. 
C-reactive protein also tended to be higher with the very low-carbohydrate diet in our study, 
 In conclusion, our study demonstrates that commonly consumed diets can affect metabolism and components of the metabolic syndrome in markedly different ways during weight-loss maintenance, independent of energy content. The low-fat diet produced changes in energy expenditure and serum leptin that would predict weight regain. In addition, this conventionally recommended diet had unfavorable effects on most of the metabolic syndrome components studied herein. 

So people who ate a very low carbohydrate diet with all other factors being equal burned an average of 325 calories more per day than the low fat participants.  The equivalent of 1 hour of moderate exercise.  WOW, that is significant!  The C reactive protein was higher for the low carb group but during the test phase it dropped significantly from a 1.75 baseline to get well below the supposed safe threshold of 1 mg/L.

Cortisol, the stress hormone, definitely did go up for the low carb group.  This study was done on obese individuals who have probably dieted before.  In the test phase they were fed 2000 calories.  Not starvation but probably lower than they are used to on their average day.  My guess is the participants probably had tried to restrict fat in the past so this was probably nothing new to them.  I wonder how stressful it would have been to take away nutrients they likely lived on for years, carbohydrates, while replacing them with nutrients, fat, they feel would cause them to gain the fat back that they had just lost.  Could this type of diet cause an increase of stress in the short term for people not used to it....I'd say yes.

I am sure every agenda will cherry pick data from this study just as I have.  Bottom line is, this is just another reason to question conventional wisdom if you haven't already.  JAMA is probably the premier medical journal in the world.  You can be sure medical professionals will be surprised.


1 comment:

Average Married Guy said...

Thanks for posting this. I've read other studies showing how protein calorie takes "more" to burn than a calorie of carbohydrate which burns very efficiently. Interesting take on the cortisol issue of those in CW diets changing to low-carb and their relation.