Megan looks at an old photo from her mother's high school yearbook and suggests that America really isn't so much fatter than it used to be. Rather, "our standards for "thin" and "normal" have changed dramatically, which is adding to our perception that Americans are getting fatter." Maybe so, but how do you explain this data:
This really is my problem with set point theory, the idea that your body is predisposed towards a rigid, nearly impossible to change, weight range. Average weights are changing substantially between generations, but also within generations. If you look at this chart and try to compare within cohorts -- an imprecise method, to be sure, but still somewhat possible -- you can see vast differences both between and within groups. Among the 18-29 year olds, only 7.1 percent were obese in 1991. In 2001, 20.5 percent of 30 to 39-year-olds -- assumedly the same folks who were 18-29 tens years ago -- were obese. That's a significant shift, and I've never heard a convincing explanation of how set point theory accounts for it.
