Monday, July 16, 2012

The Art and Science

In 2007, Gardner et al published a randomized, controlled trial called the A-to-Z Study involving 4 diets lasting a year given to groups of obese women[43]. At one end of this diet spectrum was the ‘Ornish diet’ which is very high in complex carbs and very low in fat. At the other end was the ‘Atkins diet’ (i.e., low carbohydrate). After 6 months, the women on Atkins had lost significantly more weight, but after 12 months they were still lower but not significantly so. Interestingly, blood pressure and HDL cholesterol were significantly better on low carbohydrate than any of the other diets, and this beneficial effect remained significant out to 12 months.
After publishing this initial paper in JAMA, Dr. Gardner went back and examined his data based upon the subjects' insulin levels before they stared dieting.  When the women on each diet were divided into three subgroups (turtles) based on baseline insulin resistance, the results were striking.  In the low carbohydrate diet group, weight loss was similar in the most insulin sensitive (11.7#), and insulin resistant (11.9 #) women.  HOwever weight loss with the high carbohydrate (Ornish) diet was much greater in the insulin sensitive (9.0 #) than the insulin resistant (3.3 #) women.  

Thus the most insulin sensitive sub-groups of women experienced a similar weight loss when assigned diets either high (9.0 lbs) or low (11.7 lbs) in carbohydrate In contrast, the sub-groups that were insulin resistant fared very poorly when assigned a diet high in carbohydrate (3.3 lbs lost) compared to a low carbohydrate diet (11.9 lbs). Specifically, those women with insulin resistance lost almost 4-times as much weight when dietary carbohydrates were restricted[44]. Simply put, insulin resistance strongly influences how we respond to different diets. This validates the concept that insulin resistance in essentially an expression of carbohydrate intolerance.  Dr. Gardner's data clearly demonstrates that rather than forcing an insulin resistant body to deal with a macronutrient it can't handle well this condition is best treated with a diet that limits carbohydrate.
The Art and Science of Low Carbohydrate Liv...

This book is a great read, as the authors are into the same puzzle I am of sorting out metabolic derangement - but they are full time researchers and much further down the road than I am.  They have a lot to teach!  I suspect I will read this book multiple times as I did Gary Taubes' "Good Calories Bad Calories".

I count the analysis above as another shot at the "calorie is a calorie" concept of weight loss - clearly, the hormonal state of the eater has an effect on what the body does with carbohydrate calories consumed.

Here's Dr. Gardner - his study was referenced above - in a video taped summary of his study; you know it's a good study when a vegetarian tests the atkins diet and finishes by wondering "if grains may be a problem."

Here's the abstract of his study:

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