Exercise and Low Carb Diets: Two Radically Different Treatments for Obesity

Exercise and low carb diets have been used for decades to treat patients who suffer from obesity and overweight. While these two therapies don't seem that different -- after all, exercise is exercise, and diet is a diet, right? -- the fundamental theories behind the two approaches could not be more dissimilar.

KEY POINT: Decreases in blood insulin levels appear to associate closely with weight loss.

The notion that exercise would help us lose fat derives from the common interpretation of the 1st law of thermodynamics, the Caloric Balance Hypothesis. This tells us that eating excess calories makes us fat, and that 'burning off' calories makes us thinner.

The theory behind low carb diets interprets the first law in a very different way. The Lipophilia Hypothesis, as it's known, says that disorders of the fat tissue itself -- not excess calories -- make us fat. In particular, the hormone insulin drives us to accumulate fat in our fat tissue, thus influencing our appetite and metabolism. Low carb diets work because they stop us from over-secreting insulin, thus helping us to normalize our fat tissue; and thus they solve the energy balance problem in a different way.

So we have exercise and low carb diets. Two different approaches to weight loss. Two theories with different predictions about the root cause of obesity.

Lipophilia tells us that reductions in serum insulin levels should lead to weight loss, even in the absence of calorie restriction or an increase in exercise.

And in fact, data abound to validate that prediction about exercise and low carb diets. Consider a few randomly selected articles:

1. "Suppression of insulin secretion is associated with weight loss and altered macronutrient intake and preference in a subset of obese adults."[1]

2. "Dietary fiber, weight gain and cardiovascular disease risk factors in young adults."[2]

This study promotes the idea that fiber protects against weight gain and cardiovascular problems, an assertion that Gary Taubes debunks at length in Good Calories Bad Calories. Nevertheless, it does offer more evidence that health authorities acknowledge that insulin coincides with weight regulation:

"Dietary composition may affect insulin secretion, and high insulin levels, in turn may increase the risk for cardiovascular disease."

3. Here is another randomly plucked study: "Modest weight loss and physical activity in overweight patients with chronic liver disease results in sustained improvements in alanine aminotransferase, fasting insulin, and quality of life."[3]

From the conclusion:

"These findings demonstrate that the maintenance of weight loss... results in a sustained improvement in... serum insulin levels, and quality of life."

So changes in serum insulin levels clearly associate with changes in weight and fat metabolism. These studies seem to align well with Lipophilia Hypothesis predictions about exercise and low carb diets.

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