Two Competing Theories as to Why Americans Have Stopped Gaining WeightS

Do you think obesity rates in the United States are on the rise? Despite what you've heard, they're not. The Centers for Disease Control says obesity rates plateaued for men, women, and children in the late 2000s.

In addition to the CDC report, a recent Journal of the American Medical Association article points out that the obesity rate for women and children has remained steady for ten years, while the rate of male obesity remained steady for five.

Will this trend continue? And what's behind it: societal pressure, or a natural biological limit to the obesity of the population?

A biological or societal limit?

Widespread awareness of the impact of fatty foods, and the surfeit of fat and calories in cheap, high-calorie foods over the past decade could very well be playing a role in this plateau effect. If you've had access to mass media or any public health information, then you're aware that fast food is contributing to America's health problems. But the idea of a biological limit on obesity is also quite intriguing.

Dr. David Ludwig, Director or the New Balance Foundation Obesity Prevention Center Boston Children's Hospital, explained the biological aspect in a New York Times article saying that the calories are used for:

(M)aintaining and moving around that excess tissue, [...] a population doesn't keep getting heavier and heavier indefinitely.

This is an interesting perspective, since it places physical limits on obesity from a energy standpoint. This point of view, combined with the lifestyle limits placed on obese individuals, could explain at least a portion of the plateau.

Meanwhile, there's some reason to believe our methods of labeling people as "obese" are flawed enough to render the CDC report almost meaningless.

The CDC considered those with a body mass index of 30 or more to be obese. BMI can be a tricky indicator, given that it's a function of both height and weight — with many athletes falling in or near the obese range. Major League Baseball Triple Crown candidate Miguel Cabrera is nearly obese at a BMI of 29.2, his teammate and self-proclaimed vegetarian Prince Fielder comes in with an astounding BMI of 38.4, and NFL quarterback and ESPN mainstay Tim Tebow comes in at 29.5.

While the BMI uses two pieces of data to determine obesity, a better estimate could be the newly created Body Volume Index. The BVI is calculated using height, weight, waist to hip ratio, the circumference of an individual's hips, and three-dimensional imaging to determine obesity.

It will likely be a few decades before we have enough statistics on BVI to establish obesity trends, but the impression obtained during those decades will truly determine whether the United States is hitting a period of Peak Fat, or if the calculations used to determine the plateau are flawed.

Top image by Maska/Shutterstock.com.