The Unscientific Science of Losing Weight …

So, Rebecca Watson at Skepchick decided to try to criticize the article by Olivia that I just talked about. What Watson’s trying to do is this:

Again, I want to stress that I agree with Olivia’s primary point: fat shaming is not about secretly wanting a person to be healthy. Additionally, it most likely doesn’t work as a way to motivate people to lose weight or to get healthy.

But again, that message gets lost when those fighting for the overweight and obese use bad science and bad arguments to make their points.

Unfortunately, Watson doesn’t use particularly good arguments or particularly good science to do that. Let me skip her talking about juice cleanses, and get into her talking about “starvation state”:

That said, I’m calling this out because of the use of the term “starvation state.” This is a nebulous and frequently misused phrase, sometimes referring to the idea that eating too few calories will actually cause you to gain weight, which of course is utter nonsense. If you eat fewer calories than you expend, you will lose weight. It is physically impossible to gain weight while eating at a deficit. If your goal is to lose weight, you must eat at a deficit.

In most cases where I’ve seen this used, even to talk about gaining instead of losing weight, it isn’t a claim that you will gain weight being in that state. What it refers to is the fact that you will go on a diet, lose a lot of weight, and then return to a lifestyle and amount of calories that you should be eating for your height, weight, gender and activity level … and then gain all of the weight you lost back and more besides. In short, the idea that starvation-style diets actually end up leaving you unable to maintain healthy eating habits because your metabolism has been slowed so much that it relies on far less calories than it should. Also, I recall reading a claim that when you recovered from such a state, your body tended to store fat faster, and in fact dedicated more of its resources to storing fat than it would otherwise. As I said in the previous article, I think the jury’s still out on that one, so I’m a bit skeptical (but not a chick in any sense of the word).

So I agree with Watson when she says this:

It is possible to eat too few calories to maintain a healthy lifestyle, and this can lead to serious problems, which is why most science-based weight loss regimens will suggest that you only lose about 2 pounds per week (so eating at a deficit of about 1,000 calories per day, give or take), unless you’re morbidly obese.

In fact, I’m aiming for about one, just to avoid my body getting used to this too easily and also so that I can use a burst of activity to overcome the hump. But her intense skepticism of “starvation state” seems to be at best a misunderstanding of what that claim typically is, and it seems to me of what claim Olivia actually made, although Olivia does seem to tie it more to strong starvation diets rather than the more moderate approach that Watson talks about.

And, as it turns out, seemingly did:

” It’s simply untrue that (moderately) restricting your calories leads your body to do anything unhealthy. Millions of people do it every day. I did it two years ago when I realized that I had pudged up a bit more than was good for me during a long Buffalo winter. I cut my calories down to about 1,200 per day, which, yes, is fewer than my body was using. That’s how I lost about 20 pounds over the course of about 10 weeks. When I was at my desired weight, I bumped up my calories very slightly so that I stopped losing weight. My current caloric intake is still a “deficit” from where I was before, but obviously now I am maintaining weight instead of losing it because I lost weight and my body doesn’t need as many calories.

Watson very much equivocates on “deficit” in these discussions. When people talk about deficit in relation to weight loss, they mean that the person is taking in less calories than they burn, which is why they lose weight. Here, Watson says that she’s still in “deficit”, even though presumably she’s eating roughly the same amount of calories that she expends, as she compares it to what she was eating before. That’s not the sort of deficit that Olivia talks about, and also highlights a potential issue with her analysis. The argument that Olivia is referring to — and that her sources seem to refer to, from my quick skimming of them — is the one that says that your body will go into a mode that tries to conserve calories because it isn’t getting enough of them, lowering your metabolism overall, and studies that showed that the metabolism doesn’t increase for quite some time after you stop dieting. This means that, if we take Watson’s case, Watson’s “break even” maintenance calories intake is actually lower than it ought to be for someone of her gender, weight, height, age, activity level and political affiliation (that last one is a joke). This means that if she actually ate what medical science said was a healthy caloric intake for her, she’d gain weight. This would clearly be an issue.

Watson continues this when talking about metabolism:

As for “metabolism,” see my earlier point about how I now eat fewer calories to maintain myself at my current weight compared to my weight two years ago. Yes, your metabolism will drop a bit as you take in fewer calories and lose weight. That’s normal and healthy. As Olivia’s citation shows, it will go up again if you start gorging. That’s how metabolism works.

It is not generally the case that your metabolism increases just because you start eating more or, rather, more than what you should, as Watson seems to indicate with “gorging”. When you diet, your metabolism decreases, not because you have less weight, but because your body is trying to fulfill all the demands placed on it through the direct calories that it’s taking in. So once you go off the diet, the common-sense intuitive theory is that your metabolism will increase, but it won’t go up a massive amount. At best, it will return to normal for someone with your gender and … well, you get the idea by now. The studies show, however, that it won’t in fact, go back up to normal right away, and the studies I’ve seen have hinted that it could take years for it to return to normal, which is one of the explanations for why people who diet to lose weight often gain it all back and then some: they can’t even eat what they should anymore because their body is too used to not eating that much and is trying to conserve calories.

I, personally, suspect that the more moderate weight loss coupled with an increase in exercise and activity can avoid this, by not triggering the body to react sharply to a reduced caloric intake — because it’s not very extreme — and because exercise, from what I understand, can increase your metabolism. Yes, you need less calories as you lose weight because you have less weight to move around, but you’d still want to have a normal metabolic rate (ie how much your body burns doing nothing) and not a lower one, which is what at least crash diets might be leaving you with. So Watson doesn’t really get the argument here, and so her response is, well, not a good one and does seem to be at least misinterpreting the science.

Finally, on BMI:

I’m one of the people who uses the BMI scale (for myself). It’s true that it was created as a statistical tool, and one that is used often and to good effect in studies like this one showing that pregnant women with obese BMI experience a higher risk of complications. But of course there are other studies showing that while very high BMIs are unhealthy, there are sometimes better methods for gauging mortality, like large waist circumference.

So BMI doesn’t apply to every individual, but it’s also true that it does apply to most individuals. If you’re not a body builder or other elite athlete, BMI is a much better way to gauge whether you’re at a healthy weight then just looking at your weight alone, for the simple reason that it takes into account your height.

The problem with BMI is that it typically doesn’t take anything other than height into account, which means it leaves out things like musculature and bone mass, all of which can contribute to your weight. This means that it often seems to advocate rather unrealistic ideal weights, that people massively struggle to achieve and likely can’t. For example, for me, a “normal” weight for my height would be about 170 pounds. I haven’t been that since very early high school … which included the summers where I lost a lot of weight, everyone said I was in great shape, and I was piling lumber all summer and so likely actually in the best shape of my life. And that’s assuming that I’m actually 5’9″, which might not actually be true. I’m at about 200 pounds now and was about 180 – 190 in high school. It just doesn’t seem possible for me to get down to that weight.

So, the problem I have with BMI is about what it advocates as your “ideal” weight. Sure, if your BMI is “obese”, then you definitely should lose some weight, but if you’re in the overweight range, does that mean that you should lose weight or not? Even Watson’s examples are about the high end — ie the obese category — and not about the overweight category. But BMI talks about more than just “obese”, it sets out an arbitrary idea of what “normal” should be, one that most people find ridiculous when they actually look at it and compare it to their past history. And as far as I can see, there isn’t enough scientific evidence that the normal and overweight categories are actually useful or meaningful. Which is why I’ve chosen the roughly equivalent arbitrary marks of < 200 pounds and at least not obese on the BMI. I refuse to try to achieve the mostly impossible ideal of "normal".

Especially since I might want to add on some muscle later and know what impact that can have on BMI (since muscle weighs more, adding muscle means adding weight without adding height, so …).

Ultimately, at the end of it all, Watson is arguing against bad arguments and bad science with … bad arguments and bad science, at least as far as I can see. I skipped all the Chastain stuff because Watson's probably right about it and I don't care besides, but at the end of it all we need arguments that make sense and are backed up, not appeals to the laws of physics based on a misunderstanding of the argument (see the comments for the context of that one). Answering bad arguments with bad arguments is not a way to improve the argument.

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One Response to “The Unscientific Science of Losing Weight …”

  1. So, am I a hypocrite? | The Verbose Stoic Says:

    […] talked a few times in the past about weight loss, and talked about various approaches and the importance of exercise […]

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