Does this Study Really Say You Can't Be Fat and Fit?

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This study came out almost two years ago, but it came up in a talk I gave this week, so I thought I’d post about it. CNN ran a headline that said “Fat but fit’ is a myth when it comes to heart health, new study shows.”

The study is Joint Association of Physical Activity and Body Mass Index with Cardiovascular Risk: A Nationwide Population-Based Cross-Sectional Study. In the CNN article Alejandro Lucia who is a professor of exercise physiology and the lead author of the study, was quoted as saying “One cannot be ‘fat but healthy.’ This was the first nationwide analysis to show that being regularly active is not likely to eliminate the detrimental health effects of excess body fat.“

Except that’s not remotely what his study showed, and not just because it was in no way designed to draw that kind of conclusion.

Let’s start with what the study actually did. It looked at self-reported activity data from 527,662 adults from Spain. They grouped the subjects based on BMI (and we already know the use of BMI reflects a lack of scientific rigor but we’ll move past that for now.) Then they classified the activity level into three groups. No activity was considered “inactive,” less than 150 minutes of moderate or 75 minutes of vigorous activity per week was labeled “insufficiently active,” (and since words matter, I would suggest that this label is unnecessarily judgmental and ableist,) and finally, 150 minutes of moderate or 75 minutes of vigorous activity per week or more was labeled “regularly active.”

The study’s goal was to look at the impact of exercise on risk factors for cardiovascular issues, including diabetes, high blood pressure, and high cholesterol. Note that they didn’t look at actual cardiac incidents (like heart attacks or strokes,) they just looked at factors that may raise the risk for such incidents.

So what did they find? Well, to quote their own paper

In summary, increasing PA [physical activity] levels appear to provide benefits in an overall dose-response manner (regularly active > insufficiently active > inactive for the risk of hypertension or diabetes) across BMI categories and should be a priority of health policies

Wait…what? You read that correctly – What they found was that activity provided health benefits to people of all sizes (which is consistent with the findings of (not that these links contain language that pathologizes higher weight bodies varying degrees of weight stigma) and Gaesser and Angadi, Wei et. al. and Matheson et. al, and Barry et. al. which found “Therefore, fit individuals who are overw*ight or obe*e are not automatically at a higher risk for all-cause mortality.” (And as always, a reminder that health is an amorphous concept, is not an obligation, barometer of worthiness, or entirely within our control)

So why are they claiming that you can’t be fat and fit? Well, because they found that fatter people’s risk factors were not mitigated to an equal level with thin people’s risk factors. Their (unsolicited) recommendation? “weight loss per se should remain a primary target for health policies aimed at reducing CVD risk in people with overw*ight/ob*sity.” (With a reminder that those are terms that were literally invented to medicalize and pathologize fat bodies and that person first language for fat people is a terrible idea and also excuse me while I bang my head on my desk for a couple minutes.)

This is where we see perhaps the most common mistake that is made in this type of research. They assume that if fat people have higher risk, then it must be due to their body size, and that making fat people look like thin people is the solution. This is the kind of mistake that would get you failed in freshman research methods class, but it consistently makes it past peer review in articles around weight and health.

In order to avoid making a correlation vs causation error (one of the most basic concepts in research methods) we have to, at the very least, ask ourselves if there are other things that could cause these different outcomes in fat people. And, as it turns out, there are. Peter Muennig’s research found that the stress of constant weight stigma is associated with risk factors, and Bacon and Aphramor found that weight cycling (aka yo-yo dieting which is, by far, the most common outcome of weight loss attempts) is also associated with risk factors.

That means that when the study authors (whose language, especially in their intro paragraph, suggests that they are coming from a deeply fatphobic place) claim that exercise can’t fully mitigate the risk of being fat, what they very well could have actually found is that exercise can’t fully mitigate the risk of being constantly stigmatized and/or encouraged to diet repeatedly.

That makes their recommendation that “weight loss per se should remain a primary target for health policies” even worse than it originally seemed (and it originally seemed pretty bad..) First of all, they did not in any way study whether or not weight loss 1. is achievable or 2. lowers risk factors for cardiovascular incidents, so they have no basis in their own research on which to make that claim, and no basis in other research either.

It’s important to understand that these are, in fact, two different things. So in order to recommend weight loss as a health intervention you would need:

1. Research that shows that weight loss is likely to be achievable and maintainable long-term (if not then there’s no point in making it a recommendation regardless, it’s like recommending levitation to solve knee pain, it might take the pressure off the joint, but since it’s not likely to work, it’s not an ethical, evidence-based intervention)

2. Research that shows that weight loss has positive health impacts, including when measured against any risk associated with weight loss attempts

Let’s start with #1. They don’t have that. What we know from other research is that by far the most common outcome of intentional weight loss attempts (about 95%) is short-term weight loss followed by long-term weight gain, with up to two-thirds of people gaining back more than they lost. So they are using the platform of this research to recommend something that has the opposite of the intended effect the majority of the time. Not a good look.

Onto #2. They don’t have that. There is no study that compares those who have maintained weight loss to those who are fat to see if there are health outcome differences. Their recommendation is based on the assumption that if you make fat people look like thin people, they will have the same health outcomes, which ignores the possible impacts of weight stigma and weight cycling, and is roughly like saying that, since cis male pattern baldness is correlated with a higher risk of cardiovascular incidents, the solution is to figure out how to get all the bald folks to grow hair.

So does that study really mean you can’t be fit and fat? No, it doesn’t. That study means that, yet again, research that would have earned me a well-deserve F in freshman Research Methods class is instead getting CNN headlines, because when it comes to weight and health research any fatphobic nonsense will do.

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*Note on language: I use “fat” as a neutral descriptor as used by the fat activist community, I use “ob*se” and “overw*ight” to acknowledge that these are terms that were created to medicalize and pathologize fat bodies, with roots in racism and specifically anti-Blackness. Please read Sabrina Strings: Fearing the Black Body – the Racial Origins of Fat Phobia and Da’Shaun Harrison: Belly of the Beast: The Politics of Anti-Fatness as Anti-Blackness for more on this.