The “Exercise Plateau” Paper.

Making the rounds at the moment is this new paper which purports to show that increasing exercise doesn’t increase calories burned, after a certain threshold. Their methods are a bit crude (estimating activity from wristwatch accelerometers like Fitbits, and comparing to measures of total calories expended that I don’t quite understand). There are a couple of basic caveats that ought to be mentioned up front too. I don’t know how relevant it is, because I don’t know if different races exhibit different exercise response, but their sample was heavily African and African-derived. Their sample was small, only 332 persons, and they had only mediocre compliance with their regimen.

But let’s take the study at face value for a moment. This study, and others, support the general idea that the human body will, in response to changes in diet and activity, up- or down- regulate the basal metabolic rate to compensate. This is unsurprising, if in some cases dismaying. I’ve seen it in my own life: I’ve run like hell for two straight years now and not lost an ounce of weight. And I don’t think I’m eating all that much more.

However, I did lose fifty pounds prior to that. I lost it by going from a sedentary lifestyle to an active one while not increasing my food intake. And this study supports that claim: going from minimal activity to significant activity has an enormous increase in calories burned. That’s just not the part that gets the headlines. It also says that you need to exercise a LOT before you hit the plateau.

Their main measure of activity is “counts per minute per day” on an accelerometer. This means that if you walk for an hour at two steps per second, you achieve a CPM/d of 5. The plateau doesn’t kick in until you hit CPM/d of 230, according to the researchers. That’s the equivalent of walking for 46 hours a day. So clearly, we’re talking about some SERIOUS exercise here. Casual exercisers are not going to reach these levels.

**EDIT: The author states that walking represents much more than this, and that the CPM/d where the plateau starts is around 6000 steps per day. 

So what this means is, yes, our bodies behave counterintuitively at extremely high levels of activity. But I’m not there, you’re not there. You’d have to be a serious athlete or have an extremely demanding job to hit the threshold where you start not increasing caloric output for increased activity. Either that, or their numbers are screwy, which seems as likely.  Also note that this was a cross sectional study, not a longitudinal one. That means they didn’t test individuals as their activity increased. So we know nothing about what happens when you or I increase our effort. We only know that in this population, individuals who naturally had higher activity levels also were more efficient.

So here’s the deal: the only reliable way to lose weight is to eat less and exercise more. Individuals vary in their genetic makeup that makes it easier for some and harder for others. There are no shortcuts. People who don’t care about fitness don’t have to. Judging people based on their size is petty and hateful. Don’t do it.

For the vast majority of us, “eat less and exercise more” is good advice. We have the power to influence our physical condition. Very few of us are at the margins where BMI is a bad metric, or where increasing activity won’t increase our caloric expenditures much. We have agency. If we want to make changes, and are disciplined about it, we can. Results like this are erroneously used to demoralize people and tell us our condition is out of our hands, when that’s not what the data show.