Metabolic Advantage

The concept of a metabolic advantage with low carb diets is hotly debated. A quick MegaSearch shows hundreds of articles and blog posts, including some spirited debates. So what is this so-called metabolic advantage?

Dr. Michael Eades explains it this way:

When two groups of subjects both eat the same number of calories (but provided by diets of different macronutrient compositions) and maintain the same activity level, yet one group loses more weight than the other, the group losing the greater weight is said to have a metabolic advantage. Or, more specifically, the diet driving the weight loss is said to provide a metabolic advantage.

The debates among doctors, researchers and advocates sometimes gets heated. I won’t post a link to the profane and, in my opinion, irrational posts by Dr. Eades’ opponent in that particular debate, but Dr. Eades includes it in his blog post.

The literature does show an apparent metabolic advantage in studies. Just this week (March 2, 2011) the American Journal of Clinical Nutrition published a new study, Short-term weight loss and hepatic triglyceride reduction: evidence of a metabolic advantage with dietary carbohydrate restriction:

The aim of this study was to determine the effectiveness of 2 wk of dietary carbohydrate and calorie restriction at reducing hepatic triglycerides in subjects with NAFLD [Non-Alcoholic Fatty Liver Disease].

NAFLD, or “Non-Alcoholic Fatty Liver Disease” is a condition where the liver “gets fat”, resulting in reduced liver function. It is growing at an alarming rate, with some pointing towards increased fructose consumption as a likely cause (fructose is metabolized by the liver).

Like other studies, this one notes a “metabolic advantage” with a low carb diet:

Two weeks of dietary intervention (≈4.3% weight loss) reduced hepatic triglycerides by ≈42% in subjects with NAFLD; however, reductions were significantly greater with dietary carbohydrate restriction than with calorie restriction. This may have been due, in part, to enhanced hepatic and whole-body oxidation.

The phrase “significantly greater with dietary carbohydrate restriction than with calorie restriction” is the evidence the researchers note as a “metabolic advantage.”

The hotly contested debate will continue, of course, but as evidence mounts that lower carb diets result in greater weight loss and less hunger than calorie reduced calorie diets, can the debate sustain itself for very long?