Friday, May 18, 2012

More on the latest LC/LF Diet Comparison Study, and Why LF & CRD's "fail"?

I thought of just updating the last post, but this is long enough on its own to warrant a Part II of sorts.  If you haven't read it yet, may I suggest:  LC v. LF Diet Comparison Study Shows Calories Determine Weight Loss.  What distinguished this study from many other comparison studies, was that there was an attempt at keeping calories constant between the diets.  Usually LC is ad libitum, which, especially the first time one follows a low carb diet, tends to substantially spontaneously reduce caloric intake more than what is generally prescribed for a "responsible" calorie restricted diet (CRD).  This was also a longer term study and also compared two different fixed prescribed diets rather than the usual Atkins-style induction/progression formula.  Presuming compliance, then, the study controlled for calories and sought to look at the effects of just the macronutrient composition of the diet.  

In my opinion, the rather negligible differences for both groups after a year and continuing through two years show that neither dietary intervention was particularly effective, resulting in under 10 lbs weight loss and only transient improvements in HbA1c as measured by one method only.   So why was that?  Well, the prescribed caloric intake was fixed at 1600 cal/day for women and 1800 cal/day for the men.  Right there this part of the study design pretty much doomed it to failure.  While men generally have higher caloric needs than women, total daily energy expenditure varies so widely between individuals that clearly some women have higher needs than some men, and some men and women have higher needs than others of their gender.
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