Can Eating Low Carb Foods Lead to Weight Loss, Even When Calories are Unrestricted?
Low carb foods -- such as bacon, butter, and lamb chops -- are by definition high fat foods. But our health authorities have been warning us for decades now to avoid fatty foods, because they supposedly lead to weight gain, heart disease, and other problems.
So why then do people on low carb diets seem to lose weight and feel better?
If you believe the Caloric Balance Hypothesis, the idea that eating low carb foods could be healthy makes zero sense. After all, fats are more than twice as caloric per gram than are carbohydrates, and every diet authority in the world (pretty much) tells us that the key to weight control is calorie control.
The alternative hypothesis about why we get fat -- the Lipophilia Hypothesis -- gets around this paradox. The theory says we accumulate fat in response to elevated insulin levels. Eating low carb foods works because these foods do not cause us to over-secrete insulin.
Author Gary Taubes quotes an endocrinologist from the University of Wisconsin named Edgar Gordon, who in 1963 wrote in The Journal of the American Medical Association that it could be "stated categorically" that we cannot store fat -- and thus become obese -- unless we metabolize glucose. And since we need insulin to get glucose into most of our tissues, "obesity is impossible in the absence of adequate tissue concentrations of insulin."
To sum up, high carb foods make us fat because they elevate insulin. Low carb foods make us thin because they allow insulin levels to normalize at a lower level.
For a more detailed discussion of how this all works, the site's authors advise you to read pages 352 and 353 from Good Calories Bad Calories, in which Taubes discusses the work of Pennington, one of the key contributors to the ideas of the Lipophilia Hypothesis. This explains how low carb foods stimulate the release of fat from the fat tissue to be burned as fuel. Without glucose or insulin to get the body to store fatty acids as triglycerides in the fat tissue, you can't get fat, even if you eat a very high amount of calories.
So that's the theory. Our two competing hypotheses make two very different predictions about what happens to people on low carb diets.
The mainstream hypothesis (Caloric Balance) tells us that people who lose weight on these programs must be manipulating energy balance, which then causes the weight loss.
The alternative hypothesis says the reason low carb diets work has nothing to do with how they manipulate energy balance; it has to do with how they manipulate the fat tissue itself, which in turn regulates calorie intake and expenditure.
So which is right? Is it calories that "count"? Or is it insulin?