The uptick in BMI among professional baseball players coincides with the steroid era, although there were also advances in nutrition and training that could explain weight gain.
In the last 25 years, obesity has soared in Major League Baseball and being overweight is now the norm, according to a new study from Penn State University.
The findings, appearing in Obesity Research & Clinical Practice, review the dimensions of players from 1871 through 2015, and find that for well over a century, the build of most professional ballplayers stayed within what the CDC still considers a “normal” range—having a body mass index (BMI) between 18.5 and 24.9 kg/m2.
But, starting in 1991, players’ average BMI began rising, and now 80% of players are at least overweight, meaning their BMI is 25 or higher. The CDC defines obesity has having a BMI of 30 or higher.
The researchers note that the steady climb coincides with baseball’s infamous steroid era, when players began using performance-enhancing drugs to hit balls farther, recover from injuries faster, or, for pitchers, throw balls harder.
Researchers used the Lahman Baseball Database, which records a player's height, weight, and age during their debut year in Major League Baseball. Even though the data are self-reported, the increasing upward trend could be cause for concern.
“The data are observational and raise more questions than they answer,” cautioned David E. Conroy, PhD, the lead author who is a professor of kinesiology at Penn State. “BMI can be misleading, because it doesn’t take body composition into account. What kinds of pounds are players adding? Are they mostly muscle, or fat?”
Steroids have been associated with weight gain and the ability to add muscle, along with other distinctive characteristics, such as acne, high blood pressure, and male pattern baldness. Media investigations of steroid use have frequently featured “before” and “after” photos of suspecting users, showing significant weight gain.
But the authors note that the rise also coincides with increased knowledge about nutrition, training, and mechanics of hitting, which have put more emphasis on the size of players. In earlier eras, for example, the short stop was a much smaller player. And until 1973, the American League did not have the designated hitter to replace the pitcher.
The general population weighs much more than it once did, too, but that trend began much earlier, starting in the 1970s, according to CDC data.
Conroy DE, Wolin KY, Carnethon MR, Overweight and obesity among Major League Baseball players: 1871-2015. Obes Res Clin Pract. 2016;10(5):610. doi: 10.1016/j.orcp.2016.09.003.