Is “Fat But Fit” Really a Myth?

I got an email this morning from a reporter at The Daily Meal, asking me to give my thoughts on a new study. News outlets are claiming this new research is evidence that "fat but fit is a myth" and "there's no such thing as metabolically healthy obesity." 

I won't link to the study or those articles here because they reinforce weight stigma, which is bad for your health (more on that below). But the study is called "Metabolically Healthy Obese and Incident Cardiovascular Disease Events Among 3.5 Million Men and Women," and it just came out this week in the Journal of the American College of Cardiology (after being widely covered in the media before publication).

The Daily Meal reporter, Holly Van Hare, did a lovely job with the story, so be sure to check it out (trigger warning for this and all the study links below). But of course I have a lot more to say about this issue than could fit there, so here are my unabridged thoughts: 

Weight Stigma and Weight Cycling

First of all, the study didn’t control for two likely risk factors for heart disease, independent of body size: weight stigma and weight cycling.

People in larger bodies are more likely to be stigmatized for their size—bullied and shamed in school, at home, walking down the street, and in the doctor’s office, and paid lower salaries than their thin peers in the working world—and when people internalize weight stigma, it has profoundly negative effects on their mental health.

Experiencing this stigma also raises people’s risk of chronic diseases including heart disease—regardless of actual body size. What's more, weight stigma results in people delaying or avoiding going to the doctor, which can lead to poorer health outcomes down the line. 

People in larger bodies are also more likely to have weight cycled or “yo-yo dieted” in the past, and weight cycling has also been associated with a greater risk of heart disease.

Weight cycling tends to drive people’s weight up over time; up to 2/3 of people who embark on intentional weight loss actually end up heavier than when they started. (For more on these underreported aspects of weight science, see Linda Bacon and Lucy Aphramor’s great paper “Weight Science: Evaluating the Evidence for a Paradigm Shift.”) 

Until weight science can control for weight cycling and weight stigma, we can't say that being at the higher end of the BMI spectrum causes any health conditions—even if higher weights are associated with these health conditions. Correlation does not equal causation, y'all.

Moreover, *even if* weight did have some causal effect on people’s health (which is possible, but again we can’t actually know until we control for weight stigma and weight cycling), we DON’T HAVE a known way for more than a tiny fraction of people to lose weight and keep it off permanently.

The success rate of intentional weight-loss efforts is 5% or less, by most researchers’ accounts. So for 95% or more of people, ALL diets are yo-yo diets.

And we know yo-yo diets negatively affect people’s health outcomes from the research I mentioned above!

So EVEN IF weight itself were partially to blame for the heart disease outcomes, medicine doesn’t actually have a known way for people to lose weight and keep it off. Prescribing weight loss just is NOT ethical healthcare. 

There has to be a better way. 

Health at Every Size and Health-Promoting Behaviors

That’s where Health at Every Size® (HAES) comes in. HAES is about engaging in health-promoting behaviors without pursuing weight loss, as well as working to change society to reduce weight stigma and other forms of social injustice that harm people's health. HAES approaches have been shown to have better health outcomes than the traditional weight paradigm. 

That's what I mean by ethical healthcare.

BTW, the new study also doesn’t say what the larger-bodied participants were doing or not doing to support their health during the follow-up period. The researchers only controlled for the potential confounding variables of "age, sex, self-reported smoking status, and social deprivation" (a measure of socioeconomic status, education, and employment).

The researchers didn’t determine whether the study participants were restricting their food intake and experiencing rebound bingeing during the study period, versus eating intuitively.

They didn’t determine whether participants were engaging in (and enjoying) physical activity, versus having lack of access to accommodating and welcoming spaces for movement. 

The researchers also didn’t control for whether the participants had access to compassionate healthcare providers who supported their *actual health* instead of focusing on their weight and reinforcing weight stigma.

And all three of those things can affect people’s health outcomes, again *independently of body size.*

A few other thoughts: study subjects who were in the underweight category with zero metabolic abnormalities also had greater heart-related risks (e.g. elevated risk of heart failure) than the people in the "normal-weight" BMI category. Why don’t those results get reported by the media? Why aren’t newspapers and websites trumpeting “the risks of underweight for cerebrovascular disease"? Weight bias much?!? 

The vast majority of media don’t report the nuances of these scientific studies because most reporters don’t actually know how to parse them—and I was one of them before I got a master’s in public health, so I know how it goes. Many reporters just use the press release or the abstract to report scientific studies, and others might give a cursory glance at the actual study but are just looking for confirmation of what they already believe it says.

I don’t know the exact stats, but I’m willing to bet a very small percentage of reporters who covered this story even SAW the study’s finding that people in the “underweight" category have a higher risk of heart failure than people in the “overweight” category, or that the study didn’t control for nutritional intake, physical activity level, weight stigma, or weight cycling. (I know Van Hare was one of this small percentage who did see the full study, which is awesome.) 

Mainstream health media needs to do better. But that's a story for another time. 

Last updated April 2, 2019