MD Stein - The Idea(l) of Weight
How do we define a successful diet? It’s all in the eye of the beholder, and in this case, the beholder’s era. According to the epidemiologist Traci Mann, for more than half a century, we have used the Metropolitan Life Ideal Weight Table, an actuarial exercise in insurance prediction, to standardize our measurements and categorize Americans as small, medium, or large- framed.
In the 1940’s, a five-foot, five-inch woman who weighed 200 pounds had an ideal weight of 134, which meant if she were to diet successfully, she would have had to lose 66 pounds! This was nearly impossible of course, and so in the 1950’s her target weight was changed to 160 pounds, meaning she would have to lose 40 pounds. Still, very few could do this, and in the 1960’s her ideal weight became 180, requiring a 20-pound loss. In the 1970’s, dieting guidelines changed again (due to failure rates), suggesting that one should target weight loss not in absolute terms, but rather focusing on 10% of starting weight (she would still have get to 180).
And in our constant search for greater self-esteem, the World Health Organization in 1995 defined a successful diet as one where a 5% loss occurred. Our 200-pound patient today has to lose a modest 10 pounds (which, by the way, would only drop her Body Mass Index, BMI=weight in kilograms divided by the square of the height in meters, http://www.nhlbisupport.com/bmi/, from 33 to 32) to meet our slimmer modern goal. But we’d expect her to keep that weight off for a time to call her diet a success, right? The Institute of Medicine has defined success as 5% loss for at least a year. Successful dieting, even under this culturally-specific definition, is extremely difficult to achieve. How difficult? Weight Watchers won’t release their data, but their average customer enrolls four times. Is that dieting success or just good business?