Over the last five years, as I've immersed myself in the research on weight and health, I've come to realize that a lot of what we think we know about weight and health is just not true. And a lot of our core beliefs around weight come from four core mistruths (OK, let's call them lies) that are repeated over and over and over on TV, online, in magazines and newspapers, by doctors and researchers, by friends and family, and of course in our own minds.
But you can't make good choices about your health based on lies. So let's take a closer look at what we do—and don't—actually know about weight and health.
Lie #1: Americans are getting fatter and fatter—at this rate nearly half of us will be obese by 2030.
Truth #1: There's no evidence to support this. It’s hard to get a precise handle on how pre-1980 numbers compare with today’s, though, because the definitions of overweight and obesity changed abruptly between then and now. Before 1998, the Body Mass Index (BMI) chart had only three weight categories: “underweight,” or below 18.5 on the chart, which included 2 percent of Americans; “normal,” from 18.5 to 27.3 (the cutoff for men was higher, at 27.8), which applied to 40 percent of Americans; and “overweight,” anything above 27.3 (or 27.8 for men), which covered 58 percent of the population. Those cutoffs were revised downward in 1998 to where they are now, and a category for “obesity” was added. ("Normal" is 18.0 to 24.9, "overweight" is 25 to 29.9, and "obese" is 30 and above.)
So comparing pre-1998 BMI statistics to post-1998 stats is like comparing pre-steroids home run records to those made in the age of performance-enhancement drugs. In other words, more or less impossible.
Still, we do know a few things. The average American is in fact heavier (by about twenty pounds) and taller (by about an inch) than we were in 1960. And dire predictions notwithstanding, the rates of overweight and obesity leveled off around 2000.
Why did our weight go up in those decades? Plenty of experts have theories, including what I think of as the Big Three: We eat too much; we eat the wrong kinds of foods; we exercise too little. There’s likely some truth in all those statements (for everyone, not just for those on the heavier end of the weight spectrum). But other factors have contributed to the rise as well: Many of us are poorer than we used to be, and poverty is strongly correlated with both how much you weigh and your likelihood of developing certain diseases, like type 2 diabetes (Chaix 2014; Everson 2002; Krishnan 2010; Robbins 2005; Tang 2003).
We also live with rising levels of chemical contaminants, and researchers are finding more and clearer correlations between exposure to those contaminants, levels of obesity, and levels of diabetes. The main culprits are the so-called persistent organic pollutants—pesticides, PCBs, and other compounds that build up in our food, water, and bodies—and endocrine-disrupting chemicals (EDCs) like bisphenol A (also known as BPA) (Lee 2006; Lim 2011). For instance, a 2011 study from researchers at the University of California-Irvine found that early exposure to EDCs, which are found abundantly in plastics, canned food, agricultural fungicides, and elsewhere, made mice fat (Blumberg and Aanda Janesick 2011). And a number of studies have confirmed links between the prevalence of diabetes and our exposures to persistent organic pollutants and EDCs (Dirinck 2014).
More of us take psychotropic medications, too: one in five Americans, and more than a quarter of all American women, according to a 2011 report. Drugs treating anxiety, depression, bipolar disorder, personality disorders, psychoses, and other mental-health conditions are known to cause weight gain, especially when taken over a period of time (Shrivastava and Johnston 2010).
Some nutrition experts think the low-fat craze of the 1980s contributed, too. Marion Nestle, a professor of nutrition and food studies at New York University, told Frontline a few years back that the emphasis on cutting fat out of foods led to many Americans eating more carbohydrates, which in turn triggered the weight gain. And new research suggests that our forty-year love affair with artificial sweeteners like aspartame, saccharine, and sucralose contributes to weight gain by interfering with the “good” bacteria in our guts, and thus altering our metabolisms (Suez 2014).
Whatever the causes, the rise in our average weight has translated to small gains for some and precipitous gains for a few. We're certainly not on a course that would make all or most Americans fat by 2030.
NEXT: LIE NUMBER 2: OBESITY CAN TAKE YEARS OFF YOUR LIFE.