By Jordan Feigenbaum MS, CSCS, HFS, USAW CC, Starting Strength Staff
This study, The Effect of a Plant-Based Low-Carbohydrate (“Eco-Atkins”) Diet on Body Weight and Blood Lipid Concentrations in Hyperlipidemic Subjects, by Jenkins et al. was published in the June 2009 edition of the Archives of Internal Medicine in Volume 169 (11): 1046-1054. You can read the abstract here.
If you read the whole text the authors admit that a traditional low-carbohydrate diet full of animal meats and products is good at improving just about every measurable health marker:
“Such low-carbohydrate diets have been shown to be effective in inducing weight loss, reducing insulin resistance, lowering serum triglyceride (TG) concentrations, and raising high-density lipoprotein cholesterol (HDL-C) concentrations. However, the higher meat diets have not resulted in lower low-density lipoprotein cholesterol (LDL-C) concentrations, but have tended to increase LDL-C concentrations except when vegetarian sources of fat and protein were included. This lack of a benefit for LDL-C control is a major disadvantage in using this dietary strategy in those already at increased risk of CHD.”
Aye there’s the rub! One small caveat in this otherwise perfect nutritional plan! We’re not lowering our LDL cholesterol very well, even if everything else is spot on (including the much more important HDL cholesterol count). So what does this study aim to prove?
The authors want to prove that we switch from predominantly animal meats and fats (traditional low carb/Atkins) to a low carb vegetable based diet that we can see the ever-important LDL number drop, as well as get all the benefits of more traditional low carbohydrate diets that were listed above. They end up comparing this “low-carb” vegetarian diet to a high carb vegetarian diet and get the following results:
Both groups lost the same amount of weight, 4.0kg on average. The low carb version, however, showed a greater reduction in LDL and HDL cholesterol and blood pressure values. This jives with what we typically see in low carb diet interventions with the exception of the reduction in HDL. We normally see HDL levels increase or maintain themselves on low carb diets, so why did it go down this time?
The study had its low carbohydrate group eat approximately 130 grams of carbohydrates a day, which is not “low” at all, but that’s for another argument. The diet, also known as Eco Atkins, is basically the vegetarian version of the traditional Atkins’ diet. No meat or animal products are consumed, proteins come from soy, gluten, and other plant sources. Fats come from canola oil, olive oil, nuts, and avocados but obviously, no animal fats obviously, and constituted about 43% of the diet. Additionally, carbohydrates are “restricted “(hence the Atkins’ moniker) to oats, cereals, vegetables, and so-called low starch foods, i.e. no pasta or bread.
In reality, it’s more of a calorie restricted and carbohydrate limited diet, as calories were restricted to 60% of calorie requirements. The preponderance of vegetable oil (43% of dietary calories) and lack of animal fats is the most likely culprit for the HDL dropping. Why should we be concerned about HDL levels anyway? HDL levels are known to be a much more important biomarker or health, as they help clean up atherosclerotic plaques in arteries, play a crucial role in steroid hormone synthesis, etc. Basically, we need our HDL period!
Overall, I commend that the authors of the study are trying to see what macronutrients, if any, are implicated in cholesterol levels. They also make a good case for following a low carbohydrate diet if you want improve insulin resistance, triglyceride levels, and HDL cholesterol. The issue I have with the study is it ends up supporting the Eco-Atkins diet even though HDL dropped because they were on a witch hunt to get LDL down. These days, it’s “en vogue” to recommend decreasing cholesterol levels to as low as possible, even when this does not show any improvement in cardiovascular risk or health benefits. The whole cholesterol argument is for a different day, but I just thought I’d share this study, as I found it interesting!