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


As of September 2017, new Sweat Science columns are being published at www.outsideonline.com/sweatscience. Check out my bestselling new book on the science of endurance, ENDURE: Mind, Body, and the Curiously Elastic Limits of Human Performance, published in February 2018 with a foreword by Malcolm Gladwell.

- Alex Hutchinson (@sweatscience)


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.

11 Replies to “Why weight loss isn’t just “calories in minus calories out””

  1. “The article does a good job of explaining this slippery idea …”

    I disagree; I think that Parker-Pope did a poor job of explaining the idea. She made two points that could have been stated quite succinctly:

    1. Adipose tissue has a metabolic cost. Therefore, when weight is lost by reducing adipose tissue, the total metabolic budget is also reduced.

    2. The decision to reduce caloric intake in one moment (forgoing a cookie, say) does not reduce daily intake if it is made up in another moment (say by choosing a larger portion size.)

    Of course, stating these ideas so baldly exposes the fact that only the first supports the theme: that there is more to weight than “calories in, calories out.” That makes me suspect that Parker-Pope’s poor presentation is not entirely innocent.

    I will say this much for the piece though: it makes no reference to Taubes’ obsession with carbohydrates and insulin. I remain a skeptic on this point: how can Taubes’ ideas be reconciled with the fact that people who are actually obliged to live on high-carbohydrate diets (rice, beans, potatoes) are skinnier than the rest of us? And as for the glib reference to “anecdotal and conventional wisdom for 150 years”, that is purely a fantasy of Taube’s perfervid imagination. The advent of weight gain as a social problem is far more recent. (Pop quiz: what would you guess to be the average weight of British army recruits during the first world war?*)

    And if someone does get exercise, well I can say from personal experience that it is hard, oh so hard, to have a diet that is both high in carbohydrate and high in calories. One spends practically every spare moment eating.

    * Answer: 133lb. Put’s those 25-lb soaking wet trenchcoats in perspective, doesn’t it?

  2. Thanks for the comments, Phil. I’ve found that this is a concept some people have difficulty grasping, so I thought Parker-Pope did a good job of fleshing out the idea. My experience is that saying “adipose tissue has a metabolic cost” explains everything to some people, but nothing to others.

    And that’s only part of the story. What is the metabolic cost of adipose tissue? If it was as simple as that, weight gain and weight loss would be symmetric, but plenty of studies have shown they’re not. Ultimately, of course, weight gain or loss IS determined by calories in (call it X) minus calories out (Y). The problem is that Y is a nonlinear function of X, and we still don’t know the form or coefficients of the function.

    As for Taubes, I certainly don’t know whether he’s right or wrong, but I found his book to be extremely carefully argued and impeccably sourced. At no point did he argue that weight gain as a social problem emerged prior to the Second World War — instead he argued its roots came in the 1960s and 1970s when public health advocates started calling for lower-fat diets. (The effects of what he calls the “Western diet” that would have been evident in earlier years were the “diseases of civilization” like diabetes and so on.)

  3. Phil asks, “How can Taubes’ ideas be reconciled with the fact that people who are actually obliged to live on high-carbohydrate diets (rice, beans, potatoes) are skinnier than the rest of us?”

    Really, they’re skinnier? Who? Taubes’s contention is that 150 years of clinical observation show that high-carb eaters are fatter than normal, and are particularly evident in poor populations eating modern western diets, e.g. the urban poor.

    The question is always asked about rice-based Asian populations. The answer is that these populations have trouble getting enough calories just to live, regardless of the food composition; it’s been show that dietary composition doesn’t matter much if you’re calorie-restricted. They also don’t eat a lot of sugar.

  4. I am not claiming that the metabolic cost of adipose tissue is the whole story; the point is that Parker-Pope’s story did not go beyond that, in any concrete way.

    Regarding Taubes, I was referring to the snippet you quoted and not his book. I have never been tempted to read his book, and in that respect his summary pieces may have done him a disservice. However: if his book is carefully argued and impeccably sourced, why don’t you know whether he is right or wrong? (I mean, have a sufficiently strong opinion to take a position.)

    For my part, while I am happy to disparage the advice of public health advocates, I think there are too many confounded factors to be confident that the coincidence between their rise and that of obesity can bear this carbohydrate interpretation. I find Michael Pollan’s view more persuasive, for instance.

  5. I very much agree with you about Pollan, Phil. It’s his approach that I (try hard to) follow in my own dietary practices — for instance, by eating as much fresh fruit and vegetables as I can. I certainly don’t eat anything close to a low-carb diet. (Though there’s overlap in that both Pollan and Taubes would have you steer clear of heavily processed foods.)

    The reason I can consider Taubes’ book to be carefully argued and impeccably sourced without knowing whether he’s right is that I’m not an Aristotelian. I don’t care what sounds right — I want experiments to show it! Epidemiological studies can only show correlation, not causation. And when you’re looking at outcomes influenced by as many different factors as health is, even correlation is tricky to show. (Or rather, it’s very easy to show, but very difficult to draw meaningful conclusions from the correlations that pop up everywhere.)

    What I considered to be most interesting in Taubes’ book was his very lengthy exposition of the research that has led to our current “status quo” understanding of the links between diet and health. It was absolutely fascinating. (And, given that you’re someone with a scientific outlook who’s interested in human performance and how the body works, I sincerely suggest that you might enjoy reading it.)

    Having — in my opinion — done a very good job of showing that the standards of evidence for our current understanding are extremely low, Taubes then suggests his own hypothesis to fit the existing evidence. It’s plausible to me — but in the absence of better evidence, I have no way of knowing which theory is right, or where the middle ground stands. What is needed are better studies — expensive, extensive, prospective trials. (And that’s what Taubes says too — maybe I’m right and maybe I’m wrong, but isn’t there at least enough doubt that we should study it?)

  6. Thanks for explaining that, Alex. We are perhaps in better agreement than I had supposed. I’ll put Taubes’ book on my list!

    But for the moment, I am convinced that there is nothing like exercise to teach one the connection between food and fuel – specifically, carbohydrate fuel. None sing the praises of sugar, but oh to be without it!

  7. Yeah, that was the biggest gap left for me in Taubes’ book, and the least satisfactory part of the interview — when I asked about what happens if you’re exercising at a seriously high level. It’s just not something that he has thought through carefully enough. So I was left with the feeling that (a) he might have some interesting and important insights about how the body works, but (b) those insights had little or no bearing on how someone exercising at a fairly high intensity for an hour or two a day should eat!

  8. Not in Japan a rich country.They have white rice frequently in their diet. Also Kids & People in the USA ate fries,apple pie,soda,hamburgers in the 50s & 60s there was no obesity epidemic. However portions were smaller & people it is believed were more active

  9. @Phil Koop

    It’s quite easy to have a high carb high calorie diet, i used to have one.
    Most people who eat mostly carbs, such as say poor asians who get most calories from rice don’t get an excessive amount of carbs per their glycogen expenditures (labor)

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