Brian PCF's Blog

The Battle of the Diets

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.


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.


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.


December 10, 2009 - Posted by | Uncategorized


  1. agreed this is silly. %40 of your diet is carbs? Try those individuals at 10% carbs and see what affect it has on their weight loss

    Comment by Ryan P | December 10, 2009

  2. But do we need to put them at 10% carbs if they lose weight on high carb low fat diets. What this study does it point something all of us know. Some people do just fine on low fat high carb diets. And that makes some sense. If you are insulin sensitive you don’t get flooded with insulin every time you eat some bread and it is the flooding of insulin that causes you to get fat.

    However, here is why I thin this is the exception rather than the rule.

    1. Most people who are fat ARE insensitive and so it makes sense to put them on a carb restricted diet to restore sensitivity. Fasting and high intensity exercise can also help to restore insulin sensitivity.

    2. Those eating a high carb low fat diet may be on the road to insensitivity, they just aren’t there yet.

    3. Eating small quantities and being on a semi-starvation diet has the ability to reduce insulin problems, it is just really hard to stay on for any amount of time. That people lost weight over the course of the study by eating UNDER their nutritional requirements even if it was high carb does NOT mean they will be able to do that for any extended period. But this is not surprising. 1200 calorie low fat diets make people lose weight.

    This also jives with my theory that one of the things that makes elite endurance athletes elite is that they have a body that predisposes them to being able to process carbs without insulin problems. If we hypothosize that endurance athletes really need 500g carbs a day to train (not an unreasonable hypothesis since many elite endurance athletes DO eat like that and seem to run very far and very fast) but we know what those carbs do to most people in terms of fat accumulation REGARDLESS of exercise. Maybe the difference between these two groups is not that one can run fast and one cannot. Instead it is that one group can eats tons of carbs and stay trim because they are insulin sensitive and that is what seperates them from the rest of us runner. We can’t eat like we need to eat to train like them and stay trim. Does that make sense?

    Comment by Aaron | December 10, 2009

  3. I haven’t had a chance to watch the video, but did this study look at the effects of a high carb, low fat diet and a “low carb” diet (not really low carb, but lower I suppose) on LDL particle size? Even if you aren’t insulin resistant, if all or most of your LDL is the small, dense particles, which appear to come along with a high carb, low fat diet, isn’t that a large, independent risk factor for CHD? What about HDL and triglyceride levels? I agree that some people clearly don’t need to be put on a low carb diet to lose weight, but weight isn’t the be-all-end-all for health.

    Comment by Katie C | December 11, 2009

  4. Katie, Dr. Gardner’s study did measure these and found that those on Atkins had the greatest positive improvements in cholesterol and triglycerides. The two studies I mentioned he literally talks about for about 5 minutes of the video. The first 40 minutes are about his AtoZ study which compared Ornish, Zone, AtoZ, and Atkins diet WRT weigh loss, cholesterol, and triglycerides.

    Comment by Brian PCF | December 11, 2009

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