I know, I know. That’s what I thought, too.
But then I tracked down one of the authors, Phil Maffetone, a recently retired primary-care clinician. He agreed that no term is perfect. But he’s convinced that overweight is more imperfect. In his former practice, he recalls, some patients would bring in spreadsheets of their daily bathroom-scale weights—hyperanalyzing every minor fluctuation and developing odd beliefs and superstitions about what caused weight loss, when in fact the changes in the body’s composition of water, fat, and muscle were all at play.
Obsession of that sort is only more problematic when the metric itself is flawed. The total weight of a person is a crude estimation of metabolic health, yet weight is the single most pervasive data point that most people—and their doctors—use in assessing and guiding health. The term “obesity” is currently defined by body mass index (BMI), a ratio of height and weight. “Overweight” is greater than 24, and “obesity” is greater than 29.
The scientific community has long known and accepted that BMI is imperfect. For example, because muscle is more dense than fat, bodybuilders can be categorized as obese. The more insidious problem is that people with lower BMIs, of “normal” body weight, may not be as healthy as the number suggests. These scenarios taken together have led the CDC to warn that while BMI “can be an indicator of high body fatness,” the measurement “is not diagnostic of the body fatness or health of an individual.”
Yet the world of consumer health and fitness is oriented around body weight. Almost all research about preventing cardiometabolic disease is predicated on BMI. When you hear, for example, that 66 percent of Americans (and around 40 percent of the world’s adults) are “obese or overweight”—statistics floating around news media and medical journals for years—that may be confusing the problem.
And Maffetone and colleagues see this as anything but a simple semantic quibble. They argue that people exposed to the term overfat versus overweight stand to make better-informed choices and set more meaningful health goals, because the term more accurately describes the pathology at play. Using BMI as the main indicator of obesity, meanwhile, “poses serious challenges to the accurate diagnosis, prevention, and treatment of obesity-related diseases.”
BMI might even underestimate the current scope of metabolic disease in the world. The researchers estimate that American rates of overfat may be as high as 76 percent––though by their own clear admission, the numbers are a preliminary, very rough estimate. Different techniques for measuring body fat tend to yield different results, and relatively few people have had it done by a reliable technique. Because of that, it’s also unclear where to draw a line between overfat and “normal” (and underfat). Thresholds will vary from population to population. The best example is that females have significantly more body fat than males but live longer, on average.