True, when it comes to body shape, many more of us identify with the contestants on The Biggest Loser than with the ones on America’s Next Top Model. But for the fewer than 2 percent of Americans who are underweight, food issues can be just as serious.

CNN reports that those who are naturally underweight (with a body mass index of less than 18.5) should see a doctor to determine if the cause is a medical issue—such as lactose intolerance, celiac disease, bacterial overgrowth or a B12 deficiency.

Even when the cause is not a medical issue, being underweight can lead to health problems, the network says. In extreme cases, CNN reports, it can cause difficulty fighting disease and inability to menstruate, as well as osteoporosis, anemia and other conditions.

Trying to put on pounds can be frustrating for some people, according to the network. Psychologist Linda Bacon, author of Health at Every Size: The Surprising Truth About Your Weight, tells CNN that focusing on healthy eating habits is key when it comes to gaining weight. 

“I don’t think the answer is to gain weight to meet social standards or meet some kind of arbitrary idea of health,” she tells the network. “We have so many social and health expectations that aren’t predicated on what’s true for the individual.”

Click here to read the full story.

Click here to read another fascinating news story.

Don’t miss out on MORE great articles like this one. Click here to sign up for our weekly newsletter!