The holiday season has ended and many of us who have put on a few pounds are thinking about tossing the junk food and hitting the gym. But, maybe you shouldn’t according to a surprising new study in the Journal of the American Medical Association.
The study finds that people who are overweight or grade 1 obese live longer than normal weight individuals. The researchers performed a meta-analysis of 97 studies, totaling 2.88 million people, examining all-cause mortality for people of different body mass index (BMI) groups.
The researchers compared the groups’ risk of death relative to the normal weight group (BMI=18.5-25) using hazard ratios (HR). The overweight group (BMI 25-30) had a HR of 0.94, which essentially means overweight individuals had a 6% decreased risk of dying compared to normal weight individuals. The grade 1 obese group (BMI=30-35) also had a lower risk of death (HR=0.95). However, the grade 2 and 3 obese groups had an increased risk of death compared to the normal weight group (HR=1.29).
To put this into perspective, this study indicates a 6’0” man weighing 190-260 pounds has a lower risk of death than a 6’0” man weighing 140-190 pounds. A 5’6” woman weighing 155-215 pounds has a lower risk of death than a 5’6” woman weighing 115-155.
So, should you really forgo the gym membership and invest in larger pants for the sake of health? Probably not. A multitude of previous studies have attributed beneficial health outcomes to maintaining a healthy weight or losing weight.
This is a great example that correlation does not equal causation. Many times, a study will correlate one thing to another and the media will portray it as cause and effect. More likely, there are other factors at play.
For example, the authors of the study suggested that perhaps overweight and obese individuals go to the doctor more often and receive more testing which can identify diseases at an earlier stage. Perhaps more of the overweight and grade 1 obese individuals happened to health insurance.
Additionally, BMI is not always an accurate indicator of overweight or obesity. BMI only takes into account height and weight, not body fat. A heavily muscled individual could have a high BMI yet be very lean. For example, Dwayne “The Rock” Johnson would be considered grade 1 obese at 6’4 and 260 pounds even though he doesn’t have any fat on his body. Although Duane Johnson is a physical freak, there are a substantial number of muscular individuals who may be classified as overweight or obese even though they truly are not.
This study demonstrates that we must be careful when interpreting scientific data. Many media sources love to hype stories like this one and jump to unfounded conclusions. Please don’t try to add extra weight in the name of health, and please do question the newest study results that you hear in the media.