Monday, July 2, 2012

Limits of the JAMA "Metabolic Advantage" Study

Based on the study discussed yesterday, it's worth weighing in on the limits for even a study as good as that one.  First, the weight maintenance portion of the test only covered 1 month.  That's barely long enough for people to adapt to low carb intake - meaning, it generally takes 1-3 weeks to regain the quantity of enzymes needed at the cellular level to allow fat burning in the absense of excess carbohydrate.  Maintaining the stores of catalysts at the cellular level seems to be a "use it or lose it" function like most in the human body - if you over-eat carbs all the time, you are in a chronic state requiring priority sugar disposal.  Part of that is accomplished as the cells of the body burn sugar in priority before using fatty acids.  In short, if you seldom run on fat, you lose the ability for a day's worth of running on fat. 

As an aside, I'm thinking this might be a problem for fat loss.

So, there's a possibility that the metabolic advantage that was shown over a month of low carb consumption might not be as significant if the subjects continued their low carb eating for longer periods.  I'll bet the body adapts and regains some efficiency in burning/using fat over time - meaning the metabolic advantage may have limited period of effectiveness.  If so, that's still better than being the person who's continuously bombing their metabolism with excess carbs/sugars. 

It would be interesting see what the numbers would say about the low carb intake and "metabolic advantage" over the course of a year long test.  I think it's also worth exploring whether those who are tall and thin - ectomorphs - respond differently to the MA of very low carb than do endomorphs and mesomorphs.  Ever notice that all the Biggest Loser contestants have very generous pelvic girdles?  In other words, to get Biggest Loser large, you have to start with a "large base."  This fits a generally observed pattern you are likely to recognize if you think about it - the endomorphs put on fat all over, and the ectomorphs put on fat, if at all, only on the belly.  Endomorphs have a generous helping of subcutaneous fat, ectomorphs very little.  It could be said that ectomorphs have fat averse metabolism, and endomorphs have fat loving metabolism.  If you look at the charts in the JAMA study, there is considerable variation in the individual responses to the diets.  On average, the low carb folks enjoyed a large benefit in "metabolic efficiency."  But individuals saw higher or lower result - based on their body types?  I'd like to know.  I'll be the ectomorphs benefitted less from the low carb approach.

What does all that mean in practical effect?  Almost nothing to you dear reader.  All you need to know is whether some degree of carb restriction can be made to help you reach your health and appearance and performance goals.  If your body has piled on a lot of excess fat, low carb is likely to be a great benefit.

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