Some Criticism Of That Swedish “Fat And Fit is a Myth” Study


So a new Swedish study has been making headlines:

The study, “Aerobic fitness in late adolescence and the risk of early death: a prospective cohort study of 1.3 million Swedish men”, was published in December in the International Journal of Epidemiology. The authors are Gabriel Högström, Anna Nordström, and Peter Nordström. The reason the study made headlines was its finding that “unfit normal-weight individuals had 30% lower risk of death from any cause than did fit obese individuals.” It’s an interesting study – but not nearly as conclusive as the headlines (and some internet commenters) seem to believe.

This is only one study.

Many studies have found that fitness matters more than fat, for mortality. For instance, this 2014 meta-analysis of ten peer-reviewed studies found that “Compared to normal weight-fit individuals, unfit individuals had twice the risk of mortality regardless of BMI. Overweight and obese-fit individuals had similar mortality risks as normal weight-fit individuals.”

Similarly, this 2010 meta-analysis of 36 peer-reviewed studies concluded “that the risk for all-cause and cardiovascular mortality was lower in individuals with high BMI and good aerobic fitness, compared with individuals with normal BMI and poor fitness.”1

Overall, results are mixed. I’m not saying that this Swedish study should be ignored (although it has limitations – see below). But it’s one data point among many, rather than meaning that “the debate is over,” as one person told me on Facebook.

This study only measured fitness at age 18.

This study’s method was to measure fitness of over a million young Swedish men (average age 18), and then follow them for approximately 30 years, keep track of if they died and what they died from.2

So the study didn’t measure if being currently fat and fit reduces current mortality; it measured whether being fat and fit at age 18 reduces mortality over the next three decades. That’s an interesting thing to study – but it’s hard to see how this speaks to whether or not someone like me – a 47 year old fat man – might reduce my risk of mortality with regular exercise in my current life.

Furthermore, since the study only followed male subjects, it’s unclear if these results can be generalized to women. (The study used Swedish army data from young men who were conscripted into the military; I don’t know if any comparable database exists of young Swedish women’s fitness.)

Pragmatically, it doesn’t matter, because weight-loss diets don’t work

The “can you be fat and fit?” debate ignores the fact that, for most fat people, adding regular mild exercise is achievable, and significant long-term weight loss is not.

Of course, not everyone can exercise – there are many barriers (such as health, economics, the need to care for children, long work hours, and so on…) that can prevent people from exercising. Plus, some people just don’t want to exercise, and that’s fine, too. (No one is obliged to exercise, and fat people who exercise are not better than fat people who don’t).

Nonetheless, for many or most fat people, exercise is possible, if that’s what they want. So even if in some theoretical sense being thin is better for health than exercising, that doesn’t matter for fat people like me, because being thin is not one of my available options.

  1. I want to acknowledge that the same meta-analysis also found that being fat, even for fit individuals, “was a greater risk for the incidence of type 2 diabetes and the prevalence of cardiovascular and diabetes risk factors, compared with normal BMI with low physical activity.” But it’s interesting that these risk factors didn’t translate to greater mortality. []
  2. I’m simplifying a bit for the sake of space and simplicity. []
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One Response to Some Criticism Of That Swedish “Fat And Fit is a Myth” Study

  1. 1
    closetpuritan says:

    All of those 3 big points are important. Thinking about the 2nd point, at 18 I wasn’t very active, but became much more regularly active starting in my mid-20s. For many people, especially those who played competitive sports in school, the pattern is the other way around. But that would get completely ignored by this study. Fitness at 18 seems a poor proxy for fitness throughout adult life.