Training

Why weight loss isn’t “calories in minus calories out”

March 3, 2010
By Alex Hutchinson

A few years ago, I had a long and interesting interview with Gary Taubes, the author of “Good Calories, Bad Calories”, for a piece I wrote in the Ottawa Citizen. He had a lot of interesting things to say, but the claim that stuck with me was that “calories in minus calories out” is an overly simplistic way to think about weight loss.

To think about obesity as simply consuming more calories than you expend is naïve and even meaningless [he said]. The idea that we get fat because we overeat doesn’t tell us why we overeat. If you think about it, both overeating and sedentary behaviour are behaviours, so in effect that takes the physiological disorder of excess fat accumulation and blames it on behaviour. I quote Susan Sontag in the book, who says, basically, that anytime you blame a disease on behaviour or psychology, it just tells you how little you know about the underlying mechanisms of the disease.

That’s all very well as a philosophy, but I had trouble wrapping my head around the physiology. After all, the equation of calorie deficit is so simple, how could it be wrong? An interesting piece by Tara Parker-Pope in the New York Times is what made me think about that interview. As she writes:

Numerous scientific studies show that small caloric changes have almost no long-term effect on weight. When we skip a cookie or exercise a little more, the body’s biological and behavioral adaptations kick in, significantly reducing the caloric benefits of our effort… As a recent commentary in The Journal of the American Medical Association noted, the “small changes” theory fails to take the body’s adaptive mechanisms into account.

The article does a good job of explaining this slippery idea — it’s worth a read. It also made me go back and re-read the transcript of my interview with Taubes. Here’s another excerpt that is more clear to me now than it was to me at the time:

As I point out in the book, fat tissue is regulated hormonally. Virtually every hormone in your body works to get fat out of your fat tissue to fuel your body. Adrenaline, for instance: one of the things the fight-or-flight response does is tell your fat tissue to dump fatty acids into the blood stream so that if you do have to fight or flee, your body has the fuel to do it. You don’t want to fight for like two minutes, like I did in the Golden Gloves, then run out of gas and have the crap beaten out of you.

The one hormone that tells your body to store calories as fat is insulin. And this was established unambiguously, incontrovertibly, between 1960 and 1965. If insulin levels are elevated, you can’t get the fat out of your fat tissues. Adrenaline won’t work. Neither will growth hormone. So by 1965, it was clear that the fundamental thing you have to do to get fat out of your fat tissue is to lower insulin levels. And we secrete insulin in response to carbohydrates.

So basically, by 1965, we had unravelled the biology of this longstanding belief that bread, pasta, beer, potatoes, rice and so on are fattening—something that had been sort of anecdotal and conventional wisdom for 150 years previously. But the geniuses who were involved in obesity research decided that the science was irrelevant because it implicated carbohydrates rather than gluttony and sloth.

Whether or not Taubes is right, Parker-Pope makes one thing clear (and easy to understand): If you eat one less cookie per day, you can’t just multiply the number calories in a cookie by the number of days in a year to find out how much weight you’ll lose. Your body is, unfortunately, more complicated than that.