The Battle of the Diets

Posted by Brian PCF
Dec 10 2009

This was on the Crossfit mainsite on 11/30, but wanted to make sure everybody got a chance to check it out.

Fascinating look at not only the real clinical studies that have been done comparing “low-carb” and “hi-carb” diets, but also some interesting anomalies that the low carb believers (myself included) need to take a look at.

Specifically, the comparisons Dr. Gardner points out in a study based on carb intake as compared to a fasting insulin test (about 41:30). This study showed that women who were insulin sensitive lost more weight on a high carb/low fat diet, while women who were insulin resistant lost more weight on a low carb/high fat diet. Moreover, it showed that the opposite wouldn’t happen. Meaning if you were an insulin sensitive women on a low carb/high fat diet, you would not lose as much weight as on a high carb/low fat diet.

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Realize that this study (full study here) was hypocaloric, meaning all the subjects ate less than their baseline metabolic needs. Also, there were only 21 total subjects in the study. However, Dr. Gardner shows another study (about 42:16, full study here), completely independent of the first that shows the exact same thing.

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This second study also showed that a low glycemic load (meaning a low carb) diet would result in greater weightloss for insulin resistant men and women than a high glycemic load diet, but that this wouldn’t be the case for those subjects that were insulin sensitive.

Now the first thing I want to point out about these two studies though is that the amount of carbohydrates is still extremely high from a true low-carb perspective. Both studies had the high carb group at 60% of calories and the low carb group at 40% of calories. For we Crossfitters, 40% is the absolute highest we would go for carbohydrates if we were doing strict Zone. For most of us on Paleo or reduced carb zone, we’re going to be somewhere between 10%-25% of calories from carbohydrates. As Gary Taubes, Dr. Eades, Mark Sisson like to point out frequently, a true low-carb study has yet to be done.

Now am I ready to give fasting glucose tests to everybody at the gym and prescribe a diet based on that? Not quite yet. But interesting data nonetheless.

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