Science journalist Gary Taubes thinks we've got it all wrong about fat and carbohydrates. In his new book, "Good Calories, Bad Calories: Challenging the Conventional Wisdom on Diet, Weight Control and Disease," Taubes argues that a diet rich in carbohydrates -- not excess calories or a sedentary lifestyle -- makes people fat and unhealthy. The book expands on his controversial, 2002 cover story for the New York Times Magazine in which he argued that a diet high in fat and low in carbs, similar to the Atkins diet, was more effective at controlling weight and preventing disease.
What do you want readers to take away from the book?
I want them to see how little real evidence there is to blame heart disease on dietary fat and cholesterol. I want them to see the evidence for blaming it on sugar, white flour and easily digestible starches like potatoes and rice. I want them to understand that it's not crackpot to say that these diseases could be caused by carbohydrates; it's a legitimate conclusion from the existing evidence. I want readers to understand that obesity is not about the quantity of calories we consume -- it's about the quality. Then I want them to give the book to their doctors.
If carbs make you fat, how do they do that? What's the mechanism?
You secrete insulin in response to carbohydrates -- and insulin drives fat accumulation. It's that simple. What's more, you actually need carbohydrates to store fat in fat tissue. And to get fat out of the fat tissue, you need to lower insulin levels. Other hormones like adrenaline and growth hormone also work to get fat out of the fat tissue, but they won't do it successfully when insulin levels are high -- insulin will override that.
And carbs also make you sick?
There's more than a century of evidence showing that when you add sugar, flour and white rice to any traditional diet, you will get obesity, diabetes, heart disease, cancer and half a dozen other so-called diseases of civilization. It doesn't matter whether the traditional diet was high in fat and protein, like the Inuit diet, or an agrarian diet. Add these easily digestible carbs, and you get these diseases.
What's the evidence that carbs could cause cancer or Alzheimer's, as you contend in your book?
Primarily, that the risk for these diseases increases if you are diabetic or obese. As I argue in the book, this suggests that high blood sugar and insulin can be causative factors. With Alzheimer's, one symptom is the accumulation of a protein called amyloid. That protein is cleared from the brain by a protein called IDE, which happens to stand for "insulin degrading enzyme." Its primary job is to degrade insulin. Raise insulin levels and there's not enough IDE left to get rid of amyloid. This isn't controversial. It's just that Alzheimer's researchers rarely consider why there might be too much insulin to begin with -- i.e., because of carbohydrate-rich diets.
How could carbs cause cancer?
For starters, cancer cells require an enormous amount of fuel to proliferate. And so cancer cells evolve to be incredibly sensitive to insulin. Raise insulin levels, and tumor cells get the fuel they need to divide and multiply. If insulin binds to receptors on the surface of these cancer cells, they can suck in more blood sugar. So the more blood insulin is available, the more blood sugar gets into these cells. Also, insulin increases the availability of a growth factor that's been shown to cause tumor cells to go from benign to malignant and then metastasize.
What is the evidence that the low-carb Atkins diet is healthy?
First, all you're doing is not eating foods that none of us ate up until a few hundred or thousand years ago. The clinical trials show that people lose more weight on the Atkins diet than on low-fat diets or low-calorie diets, and their cholesterol profiles improve. HDL, the "good" cholesterol, goes up. Triglycerides, which are risk factors for heart disease, go down. Blood pressure goes down. All of these should reduce the risk of heart disease.
So is there no evidence that the mainstream low-fat diet is healthy?
Well, the mainstream medical community believes low-fat diets are healthy, at least low-saturated-fat diets are healthy, based almost entirely on the idea that statin drugs reduce the incidence of heart disease in high-risk patients and also lower LDL "bad" cholesterol. By their logic, a diet that lowers LDL cholesterol should also be a healthy diet. That's their fundamental piece of evidence.
Does that convince you?
I think it's insane. A statin is a drug -- we don't know what else it's doing. And what a drug does and what a diet does are entirely different things. Moreover, there's actually evidence that the benefit of statins comes from mimicking the effect of a low-carbohydrate diet, not a low-fat diet.
Could part of the reason for the obesity epidemic be the official recommendation to eat a low-fat diet?