Although appealing, don’t march to the buffet line just yet.
Weight is one of the most difficult factors to control in our busy lives. We strive to cook healthy and exercise frequently, but long hours and tight schedules can make these goals difficult. In the doctor’s office, weight has traditionally been assessed using the body mass index or BMI, a medical formula that groups individuals as normal, overweight, or obese based on height and weight.
To better understand how weight impacts our health, Dr. Katherine Flegal, a scientist at the Centers for Disease Control and Prevention, and colleagues pooled data from nearly 100 prior studies on weight and mortality. Their analysis of over 2.5 million patients showed that compared to those with a normal BMI (ex. 5’10’’ and 150 lbs.), persons with an overweight BMI (ex. 5’10’’ and 190 lbs.) have a 6 percent lower risk of death.
In addition, those who had mild obesity had the same mortality rate as those with normal weight.
Lastly, persons with moderate or severe obesity were found to have nearly a 30 percent increased mortality risk.
The results raise an important question: is it better to be overweight? Higher weights have traditionally been associated with higher risks of diabetes and heart disease, both of which reduce lifespan. Yet, Flegal’s findings suggest that those who are slightly overweight may have lower mortality. The jury is still out but this study has several take home messages.
First, patients who are slightly overweight do not need to go on drastic diets. However, healthy eating and exercising should continue to be important goals, as those in the study who had higher levels of obesity had a much higher mortality and many studies in the past have shown that proper diet and exercise lowers the risk of heart disease.
Second, BMI is a single number that should not be used in isolation. Rather, BMI should be used in combination with heart and cancer screening tests to gain a more comprehensive assessment of health. For example, if you are a diabetic and have high blood pressure, although you may be overweight, you would likely benefit from losing weight.
Lastly, BMI definitions are based on data from decades ago and may need to be adjusted to reflect modern society. Likely good news for many, the 40 percent of Americans who are currently “overweight” may become part of the new normal in the years ahead.
Anant Mandawat, a graduate of Lakeside High School and Yale University’s Medical School, is a doctor of internal medicine at Massachusetts General Hospital and Harvard Medical School.