Dear patients,
Why We Get Fat
I am sorry. I have been giving you bad dietary advice. In medical
school we learned that fat in your diet causes fat to accumulate in
your arteries, causing heart attacks and strokes, so I told you to eat
a low fat diet. Of course, looking back, we had no evidence to support
that conclusion, but it just seemed rather obvious. Obvious ideas are
often the most dangerous ideas of all. When you see a study that
might confirm your obvious idea, you give it extra weight. When
you see a study that might refute your obvious idea, you find
problems with the study. When the idea is less certain, then you tend
to give the empirical evidence more weight. This is what we’ve done
with the hypothesis that dietary fat causes heart disease.
I just finished Gary Taubes' “Why We Get Fat. It’s not a perfect book, but I do recommend it. He dispels myths about why obesity occurs, explains what really causes it, and discusses why our current medical and public health approaches to obesity are hurting rather than helping. He starts out by dispelling the myth that obesity is caused by an imbalance of “Calories In” versus “Calories Out”, and more specifically, that obesity can be fixed by reversing that imbalance. This is something I certainly believed. I’ve always told patients to eat less and exercise more. It doesn’t work. Instead of calorie imbalance causing obesity, he states that obesity (and growth in general) causes a calorie imbalance. The increased amount of fat cells require more energy for sustenance, and therefore our bodies find a way to increase the amount of calories that we take in, compared to what we expend. So, while it is true that taking in more calories than you expend causes your weight to go up, it is not true that you have much control over your calorie intake or expenditure. That’s determined by hormones. This is the part that is counter-intuitive. It would seem that I could control the amount of calories that I eat or that I spend. You might have some control over what foods you put in your mouth, buy you have no control over how the calories are extracted or absorbed. You also have no control over the lower level hormonal signals that make you hungry. Those signals have evolved over millions of years to be very powerful because in prehistoric periods, if they didn’t work, you died. It’s hard to overcome that kind of evolutionary power with “willpower”. Even if you are successful in decreasing the calories that you eat, your body will naturally decrease the calories that you burn. The variables are dependent on each other.
The villain is carbs
This leads to the next question: Why do we get obese? If it’s not a simple matter of eating more calories than we expend, then why do we get fat? The culprit is insulin. Insulin causes the cells of our body to deposit fat. Insulin, in turn, is released whenever there is glucose in our system, which is preferentially caused by carbohydrate intake. Taubes goes into great detail about the workings of the endocrine system, explaining why insulin is such a powerful factor in causing fat deposition. It also explains the phenomenon of why people who have plenty of fat still get so ravenously hungry. Insulin prevents fat from being turned into energy so muscle cells have to use carbohydrates, a much smaller pool of energy. Once it runs out, intense hunger sets in and the eating cycle starts again. Reading these chapters took me back to my med school physiology courses. I learned all of this in med school, but we were never taught to connect these well accepted facts with the things that we were being taught in our dietary lectures.
Eliminating carbs from our diet without restricting any other nutrient will stop the fat deposition process, which in turn will decrease our calorie requirements, which will cause us to lose weight. There is quite a bit of genetic variation from person to person, so some individuals will be able to tolerate more carbs than others, and not everyone will be completely lean even without any carbs.
He spends a lot of time going over the history of dietary research dating back centuries. The danger of carbs was well understood and accepted in all scientific and nonscientific circles until the last 50 years or so, when there was a change that attributed obesity to behavioral weakness. This was started by the acceptance of the calorie imbalance hypothesis. Once people accepted the thinking that taking in more calories than you expend causes obesity, it was a short step to blaming obesity on the individual for not controlling their diet or exercising more. The focus of scientific research was taken off of fat deposition and on to behavioral changes.
I had been coming around to this conclusion slowly over the past few years (and am embarrassed that it has taken me this long). I remember reading about the Atkins Diet about 10 years ago and thinking how reckless Dr. Atkins was being by suggesting something which was so obviously wrong. My thinking started to change a few years back when I saw Mala struggle to lose weight despite strictly following an 800 calorie diet. I didn’t think that kind of calorie restriction was possible, but I watched with my own eyes as she did it and still barely saw results. That opened my eyes, and over the past few years, I’ve seen more and more results with low carb diets. Results which include weight loss, better cholesterol profiles, and overall better health. Interestingly, the diet recommendations that are provided in the book are from Eric Westman, MD, a UW trained physician who works just down the street from me.
Mala and I have been trying to get healthier over the past 8 months. My brother started a Biggest Loser competition amongst a bunch of us, and Mala won the first season. We’ve been exercising with more regularity and eating better. Together, we’ve lost over 80 lbs. To complicate the points that I’ve been making in this post, we have NOT been following a strict low carb diet, and we have been counting calories. On the other hand, I’m certain we’re eating less carbs than we did before. But Mala’s focus has been on making delicious (gourmet!) fresh food using “real food” ingredients. She’s tried to cut processed food completely out of our diet. I think that makes a huge difference. We’re not meant to eat chemicals and we have no idea what these chemicals are doing to us. Optimizing food for specific criteria, whether that’s low-fat, low-carb, or whatever, is bound to have unintended consequences. In that vein, I agree with Michael Pollan’s recommendation to “Eat Real Food”.
At some point, I’d like to review all the science behind the conclusions in Taubes' book, just so I can have a better understanding for myself. I recommend that anyone treating patients (nurses, doctors, nutritionists, trainers) or anyone trying to get healthier read this book.
Some other much more entertaining and useful links: