A new study shows that an increase in average BMI over the years can’t be blamed on changes in height. Here’s what that means for our health.
American have gotten wider in recent years, but not taller, according to a new study from the U.S. Centers for Disease Control and Prevention (CDC). The report, published today by the National Center for Health Statistics, found that average weight, waist circumference, and body mass index (BMI) increased among all age groups between 1999 and 2016.
Overall, men’s average weight increased by more than 8 pounds during that time period from 189.4 in 1999–2000 to 197.9 in 2015–2016. Women’s average weight increased by nearly 7 pounds, from 163.8 to 170.6.
Average heights, however, did not see similar growth. Most groups saw no significant change in height over the study period, while some—like women of all ages, and men 40 to 59—saw an overall decrease in stature.
The results were similar among most demographics, with the exception of black men and Asian men and women. Among black men, measurements of weight and waist circumference increased until 2006, then leveled off. Asians (of both sexes) were the only group that saw no significant change in width nor height.
The study included measurements from a nationally representative sample of more than 45,000 adults, and it provides an update to a previous study of height and weight trends through the early 2000s. In that report, it was revealed that the average American weight increased by more than 24 pounds between 1960 and 2002. Average height also increased, by about 1 inch, over those four decades.
Steven Heymsfield, MD, president of The Obesity Society, says the results of this study are not surprising. “Clearly, there has been an increase in adiposity in this country,” says Dr. Heymsfield, who was not involved in the new report. Many studies have documented growing waistlines and rising BMIs over the last several decades, he says, along with increases in the prevalence of obesity-related health problems.
But the findings are still important, he says, because they show that height has not played a role in changing BMI patterns over the years. (BMI is a measure that takes both height and weight into account, so it’s influenced by changes in either.) “It proves that what we’ve suspected is correct—that BMIs are getting higher and higher, and we can’t blame it on the fact that people are getting taller or shorter,” he says. “It’s dismaying, but also reassuring for our research.”
It’s helpful that the study also looked at weight and waist circumference, says Dr. Heymsfield, since BMI doesn’t paint a complete picture of one’s health. It doesn’t take into account muscle mass versus body fat, for example, so people with a lot of the former may fall into the overweight or obese category even if they’re very physically fit. Studies have suggested that measurements such as waist circumference and waist-to-hip ratio may be better indicators of a person’s overall health.
So now that we have evidence—even more evidence, that is—that the obesity epidemic is real, what can we do about it? Dr. Heymsfield says there’s lots of ongoing research, and that scientists are making new discoveries every day.
“We’re looking at this on the molecular level, and progress has been breathtaking,” he says. “We now know that there are certain genes that predispose people to obesity, and that’s helping us to identify people much earlier in life who are at risk.” Scientists are also studying how public policy efforts—like calorie labels at restaurants and taxes on sugary beverages—can help turn the tide.
On an individual level, if you’re concerned about your weight, there’s also the age-old advice that doctors have been giving for decades: Strive to get the recommended amount of physical activity, eat a balanced diet rich in fruits, vegetables, and whole grains, and talk with your doctor or a nutritionist about obstacles that might be standing in your way. This study shows you’re definitely not alone—and provides even more incentive for Americans to reverse this troubling trend.