In season 18 of "The Simpsons," as Bart leaves the dentist's office, the hygienist hands him a gift bag, saying, "Here's a free toothbrush. Keep those teeth clean."

Bart looks into the bag and responds: "So you're saying I should do your job for you, at home, for free? You wish!" He drops the bag in the trash.

We know you would never do that. There are plenty of reasons to keep that bag, besides free stuff.

One reason is that there's a link between dental disease and obesity. In a new study published in the journal Oral Diseases, researchers found that those who were obese had a nearly six times higher chance of serious gum infection.

This may be because obese people often have higher levels of inflammation, and inflammation increases the likelihood of gum disease.

Plus, gum disease is linked to heart disease and diabetes.

In fact, nearly 22 percent of people with diabetes also have periodontal disease. And past studies have shown that gum disease worsens glucose control and makes it more likely that you'll develop non-alcoholic fatty liver disease.

So if you're carrying extra weight, make sure to see your dentist at least twice a year, and brush twice and floss at least once a day.