The Doctors share a recent study by the International Journal of Obesity which says obesity is a risk factor for flu complications and might make the vaccine less effective. 

Watch: Drs. Rx: How to Make Your Flu Shot More Effective

Gastroenterologist Dr. Jorge Rodriguez says the study looked at 1,200 patients and found that those with a BMI above 40 had almost twice the risk of getting the flu as people that did not. 

He explains that a BMI, or body mass index, of 30 qualifies someone as overweight, and one of 40, is markedly and morbidly obese.

The reason behind the study's finding is when you are overweight, your immune system is affected and you are more likely to get infections as well as less likely to be protected against them. 

Dr. Rodriguez says a pet peeve of his is when people say they are overweight but they are healthy. It may not be obvious, but the body is just not functioning as healthily as it could be. 

Watch: The First Step? 'Just Move' Says Formerly Obese Guest

The Doctors have had guests over the years come on after massive weight loss and share how their lives have improved. If you are obese, avoiding the flu is just one more reason to find your best weight.