A study published online this past week in the Journal of the American College of Cardiology, and generating widespread media attention, challenges the notion that it’s possible to be fat and fit. Or so it seems; as ever, there is some potential devilry in the details. Let the exorcism begin.
First, the argument has long prevailed that it is possible to be both fat and fit, and that fitness trumps fatness. Perhaps the best known champion of this concept is my colleague, Dr. Steven Blair at the University of South Carolina. Fundamentally, I agree with Dr. Blair. Studies suggest that being heavier but fit is better in terms of overall health outcomes than being very thin, but unfit.
But on the other hand, in the real world fit and not-so-fat tend to go together, for the most obvious of reasons: the things we do to make ourselves genuinely fit are also the best strategies for lasting weight control. Up to a point, fitness is a product of exercise, which tends to be Dr. Blair’s primary focus. But true fitness also means good metabolic health, and that is highly dependent on diet as well. Food, after all, is the fuel for the physical work of the human body.
All of which suggests that genuine fitness derives from eating well and exercise. Those are the winning strategies for weight control, too. Eating well and being active are not, of course, a guarantee of any particular weight. Weight is not a choice, and is governed by some factors we don’t control- such as genetic variation, ethnic heritage, and even our intestinal flora. And, it’s also possible to eat well, but too much.
But other things being equal, healthful eating and routine physical activity work not only for weight loss, which can be achieved with any cockamamie diet, but for lasting weight control. There is evidence of this from many sources, among the best of which is the National Weight Control Registry. The Registry now has data on over 10,000 people who have lost a substantial amount of weight, and kept it off for year. Invariably, these people eat well and exercise. It works.
So, in the real world, most people who are truly fit tend to be at least relatively un-fat; and most people who are un-fat for the long term (in the absence of a health problem to account for it) tend to be fit. A Harvard study some years ago looked at a large population divided into fit, yes or no; and fat, yes or no. There were lots of people in the “fat, not fit” cell, unfortunately. There were fewer, but many, in the “fit, not fat” cell, and the “not fat, not fit” cell. The smallest of all was “fat, fit.” The combination does not seem to be common in the real world.
Which leads us back to the new study, which headlines suggest challenges even the possibility of the combination. The study was conducted among over 14,000 adults in Korea, both men and women, lean and overweight. They were all “metabolically health” as defined by normal levels of blood lipids, blood glucose, and inflammatory markers.
Coronary artery CT scanning was performed to look for calcification, a reliable indicator of atherosclerosis. The principal study finding was that as body mass index went up, so did coronary calcification. Despite having a “normal” metabolic profile, the overweight and obese members of this cohort had more plaque in their coronary arteries than their lean counterparts.
When the researchers adjusted for finer gradations in the laboratory measures, the association was much explained. In other words, while the overweight members of the group all had “normal” metabolic markers, they were a bit less normal than among the lean members. Lipids and inflammatory markers were high normal, and so on.
From my perspective, the study left out a lot of important information. Very little was said about exercise levels or cardiovascular “fitness.” Normal metabolic indicators is not the same as being genuinely fit. There was no detail about dietary intake either, and it is certainly possible that variations in diet quality might have had something to do with variation in coronary calcification. And finally, while body composition was assessed, the results were not presented based on body fat distribution. We have long known that in terms of metabolic health and heart disease risk, all obesity is not created equal; it’s fat accumulation around the middle that matters most.
Still, the study suggests that even with other metabolic factors accounted for, excess body fat is, by itself, a risk factor for coronary atherosclerosis. That is a potentially important message that argues back against the “ok at any size movement.” Size may be ok, but coronary disease is not. If we have to control our body fat to prevent calcified plaque in our coronary arteries, that is not a body image issue; it’s a matter of potentially life and death significance.
But while this study suggests that metabolic fitness and degree of fatness may both matter, it changes nothing about how best to address both. Eating well and being active remain the best medicine both for defending against fatness, and cultivating fitness.
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