Let's start with simply looking at how to define overweight/obesity. The most common metric for determining weight status is the BMI (Body Mass Index). By using a person's weight and height the BMI attempts to be a proxy for determining body fat percentage (accurate body-fat tests are expensive and complicated). The BMI was originally developed to determine the "fatness" of a population, but because of its simplicity, has been repurposed to compare individuals*. Overweight is defined as having a BMI of 25-30 and obesity is having a BMI greater than 30. Those with a BMI greater than 40 are typically referred to as morbidly obese. Other metrics include determining a person's ideal body weight and assessing how much above/below that they are or measuring actual body fat.
The "fat & fit" side of the argument points out that the BMI fails to consider a person's unique build and the density of lean body tissue. Elite distance runners have BMIs around the 18-20 end of the spectrum while football players commonly run greater than 25, putting them in the overweight category. Does this mean they are less healthy? [and I can't type BMI this many times without pausing to calculate my own: it's 18.5]
Some studies, such as one done by epidemiologist Edward Gregg say that fitness is what matters.
"What was unexpected was those who tried to lose weight -- but didn't -- those people had a mortality benefit," Gregg tells WebMD. "And our best speculation as to the reason is there are behaviors that go along with weight loss attempts that are good for you. These may have positive effects regardless of whether a person is able to maintain weight loss. They adopt more active lifestyles, they change diets. Over the long haul they are not successful at losing weight, but these lifestyle changes seem to help." [source]
Other studies contend that regardless of fitness status, death risks are increased in overweight people. [like this one]
Body fatness is a better predictor of CVD risk factor profile than aerobic fitness in healthy men. Although habitual physical activity is an effective strategy for preventing CVD, elevated body fatness is associated with an adverse CVD risk factor profile independently of aerobic fitness.
And there are studies that are on the fence about it all, such as this one:
In recent years, the "fitness vs fatness" issue has led to controversy and heated debate. Although the debate may never be fully resolved, the relative contribution of fitness and obesity to overall health and risk actually may be a trivial matter because a common treatment is already available for both low fitness and excess body weight. Increasing regular physical activity results in predictable increases in fitness, and it is widely accepted that regular physical activity is a core component of successful weight loss programs and, more importantly, of long-term weight loss maintenance. In essence, physical activity is the common denominator for the clinical treatment of low fitness and excess weight, making the "fitness vs fatness" debate largely academic.
Weight is a convenient mode for communicating health risks to people. Everyone has a weight, it's a simple number, no variables. Physical activity and diet are messier; there are different intensities, different lengths, different caloric needs, and no easy way to count any of it. But by taking the focus off weight would people be more likely engage is exercise? Do some people fail at weight loss and thus permit themselves to also forgo a healthy diet and exercise? If diet (I use this term to define a lifetime of eating, not a short-term fix**) and exercise were the goal and not just the means would they have more staying power?
Thoughts, thoughts, and none of it will be solved with this post. In fact, hopefully, I just opened a can of worms in your mind about weight....
~L
*A soapbox issue of mine.
**Yet another issue I get rather involved in...
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