“The calorie is broken—and this is why,” says the subheading, in a kind of mantra that’s spreading every day on the internet. Here’s the thing: people have been told over and over that to lose weight they need to burn more calories than they take in, but (a) they think they’re doing that and (b) they aren’t losing weight: what gives? The calorie must be “broken.”
What they mean, of course, is that calorie counting is flawed, and that it may be making it hard for people to lose weight. The latest of these articles, a rather in-depth one over at Gizmodo, adds fuel to the fire, but I’m not convinced.
Despite saying that “none of [what’s wrong with calories] means that the calorie is a useless concept. Inaccurate as they are, calorie counts remain a helpful guide to relative energy values,” the authors nevertheless spend the entire rest of the rather extensive article pointing out how calories are a “broken” way to gauge relative energy values and looking for alternatives. But:
It is still, even now, 100% true that the only way to lose weight is to expend more calories than you take in. There is literally nothing untrue about that statement. It is not “broken.” Calories aren’t meaningless units. It is the one and only way to lose weight, save having bits of you physically removed.
The problem is that it’s hard to know (a) how many calories you’ve absorbed in a given period, and (b) how many calories you’ve burned in that same period.
The problem with knowing how many calories you’ve absorbed is because you don’t absorb every calorie you eat. Calorie counts are usually based on measurements and calculations performed using a “bomb calorimeter,” in which foods are dried and burned and the heat they produce is measured. It’s a number derived from physics. You can reasonably think of this as the upper limit of how many calories you could potentially get from a food. The thing is, however, that we often absorb fewer calories than are in a food, because we’re inefficient — less-cooked foods are less easily absorbed, especially under- or uncooked meat, and higher-fiber foods are also harder to absorb. There’s also the matter of the microbes in your gut breaking down foods to a greater or lesser degree and thereby making them more easily absorbed.
You cannot take in more calories than you eat, but you can (and often do) take in fewer.
The problem with knowing how many calories you’ve burned is due to normal human variation: your basal metabolic rate — that is, the calories you burn doing nothing but live — is responsible for the vast majority of the calories you burn in a given 24-hour period. We’ve done some pretty good science to make good rough estimates, but it can and does vary from person to person. A person’s weight, size, height, gender, age, and body composition (for example percent muscle) all seem to make a difference. In fact, you can change your BMR (at least a little) by building or losing muscle mass, even if your weight stays the same.
Does this mean it’s hopeless to use the calorie? Should we abandon it in favour of some kind of satiety index as one of the people the article cites suggests? I don’t think so.
Let’s pretend we don’t know *anything* about human metabolism (even though we do) and that our knowledge of what’s burned and what’s absorbed in your body are completely unknown to us. We’ll call this the “humans as black boxes” approach. What can we know?
Well, we can know how many calories you’re eating. That measurement will be solid, if someone’s not deliberately screwing with the numbers to get you to eat more (incentives for which are, unfortunately, plentiful). If the serving size is accurate (and it might not be) and the bomb calorimeter data is accurate (which sometimes companies aren’t forced to use, relying instead on century-old approximations) then we can know the most calories you’re potentially taking in. We know you might be taking in fewer, but we don’t know at what percentage.
We can also know how much weight you’re gaining or losing. If you’re gaining weight, you are taking in more calories than you are burning. If you’re losing weight, you’re burning more calories than you’re taking in.
Between these two things, you can figure out roughly how much you need to eat in order to take in enough calories to gain or lose weight. Especially because you’re not aiming for a hundred calories either way. Sure, your caloric estimate might be 100 off a day, but that won’t matter because, unless you’re trying to lose ten pounds over twelve months, weight loss doesn’t really deal in numbers that small.
If you want to lose a pound a week, you should aim for a weekly caloric absorption deficit of 3500 calories. That’s burning five hundred more calories per day than you’re taking in. Just so we’re clear, my BMR (as a 33-year-old male, 175cm tall and 65kg) is roughly 1600 calories a day. If I rest on my laurels all day, that’s all I burn. So if I wanted to lose a pound a week? I’d have to absorb close to a third fewer calories than I would to maintain my weight.
Because we don’t know exactly what you’re burning, though, it makes gauging how much food to eat hard. But you can (and many people do) spend time figuring out what your level of weight-sustaining activity and diet is. The growing “cult of fitbit” is a good example of this. Furthermore, humans aren’t black boxes — we really do have estimates of your daily expenditure you can start from, making the deduction of your personal burn rate easier. Once you’ve got that, you can roughly count the calories, get an estimate of what to eat to sustain, and then reduce as appropriate from there to line up with your goals. And if you aren’t losing weight, it’s because you’re still taking in more calories than you’re burning. It sucks, but it’s physics.
Now, this may be what the authors are referring to as “personalized” solutions, but it doesn’t take an army of people or a new set of economic incentives to offer the service. Nor does it take the passing of new regulations — though if you ask me, forcing companies to actually use a bomb calorimeter rather than 1800s estimates of what you might be absorbing would be a good start. It’s a matter of using the available data, drawing inferences, and recalibrating over time. It’s essentially a matter of running your own data-gathering experiment on yourself and not giving up if you’re still getting the balance right after six weeks.
In the meantime, research is continuing into the gut microbiome, as well as into other possible factors that effect how much of what you eat you absorb, like fasting and eating routines. It would be wonderful if we could eat the same amount and lose weight — and if some of the research pans out, maybe we’ll get part of the way there by making our guts less efficient at extracting energy from food.
But in terms of the calorie, well, I’m not counting it out yet, even if it’s not perfect. “Calories in vs. calories out” is still a useful calculation, if you know what it means and how to use it right.
Richard Ford Burley is a writer and doctoral candidate at Boston College, as well as an editor at Ledger, the first academic journal devoted to Bitcoin and other cryptocurrencies. In his spare time he writes about science, skepticism, feminism, and futurism here at This Week In Tomorrow.