A link from dearieme led me to a recent study that found low-carb high-protein diets — presumably used to lose weight — associated with heart disease. The heart disease increase was substantial — as much as 60% in those with the most extreme diets. (A critic of the study, Dr. Yoni Freedhoff, called the increase in risk “incredibly small“.) Four other studies of the same question have produced results consistent with this association. No study — at least, no study mentioned in the report — has produced results in the opposite direction (low-carb high-protein diets associated with a decrease in heart disease).
I find this interesting for several reasons.
1. I learned about the study from a Guardian article titled “What doctors won’t do”. A doctor named Tom Smith said, “I would never go on a low-carbohydrate, high-protein diet like Atkins, Dukan or Cambridge.” Fine. He didn’t say what he would do to lose weight. The psychological costs of obesity are huge. The popularity of low-carb diets probably has a lot — or everything — to do with the failure of researchers to find something better. I have never seen people who criticize low-carb diets appear aware of this. I disagree with a lot of Good Calories Bad Calories but I completely agree with its criticism of researchers.
2. There has never been a good explanation of the success of low-carb high-protein diets (why they cause weight loss), although this has been well-known for more than a century. (A good explanation would be a theory that made predictions that turned out to be true.) Such diets require a big change in what you eat. A big change is likely to have big health consequences in addition to the weight loss, and those side effects could be either good or bad. It now appears bad is more likely. With a good theory of weight control, you should be able to find a much smaller change that produces the same amount of weight loss as a low-carb high-protein diet. Because the change is much smaller, it should have much smaller side effects. Much smaller side effects (unknown whether they are good or bad) are much less likely, if bad, to outweigh the benefits of the weight loss. I have never come across a low-carb advocate who seemed to understand this (that we don’t know why they work and it would be a very good idea to find out).
3. The Japanese are remarkably healthy (live very long), slim, and have very little heart disease, yet eat lots of rice. Which makes absurd the notion that all high-carb diets are unhealthy or fattening.
4. The comments on the low-carb study are mostly critical and the criticisms are terrible. For example, Dr. Yoni Friedhoff, who blogs about weight control, says, “The paper’s basing all of its 15 years worth of conclusions off of a single, solitary, and clearly inaccurate, baseline food frequency questionnaire”. The authors of the study correctly reply that inaccuracy would reduce the associations.
5. Until nutrition scientists do better research, our best source of nutritional guidance may be what we like to eat. Evolution shaped us to like foods that are good for us, at least under ancient conditions. We like carbs and we don’t like foods high in protein (lean meat is barely edible) so a low-carb high-protein diet is on its face a bad idea. This is why I find it plausible that the low-carb high-protein association with heart disease reflects cause and effect (low-carb high-protein causes heart disease) and that in particular a high-protein diet causes heart disease. (Too little of the right fats?) We very much like fat. Under ancient conditions, the fat people ate was mostly animal fat and, before that, if you believe in aquatic apes, fish oil. It is quite plausible that lactose tolerance spread so quickly throughout the world because at the time everybody was starved of animal fat — high-fat mammals had been hunted to extinction — and dairy products were a good source of it.