Our society overemphasizes looks. If you look good and you are thin, the conventional wisdom goes, then you must be healthy, right? Not necessarily.

According to recent research, some people who look thin on the outside can actually be considered unhealthily plump on the inside.

Surprisingly, it turns out that about 45 percent of women and 60 percent of men who had a normal body mass index score (BMI) were still burdened with too much fatty tissue on the inside. This means that even thin people can be at risk for fat-related health problems like heart disease and diabetes. 

Let's differentiate between the two main types of fat in our body. Subcutaneous fat is the fat that's located just beneath our skin and so is most visible to others.

The other type of fat, and the one examined in the research study mentioned above, is called visceral fat. It surrounds such body organs as the heart, stomach, pancreas, and liver. We generally think of visceral fat as "belly fat," and it's much more dangerous to our health than is subcutaneous fat.

You see, fat doesn't just sit there passively in our bodies; it's always secreting hormones — and these hormones can disturb the proper communication among our organs. This is why subcutaneous fat is associated with an increased risk of heart attacks, stroke, diabetes, and some types of cancer. 

So how do you know if you're carrying healthy fat or not? Simply grab a measuring tape and determine your waist size. For women, if your waist is greater than 35 inches around, then you are more at risk for health problems. Men with a waist circumference greater than 40 inches are similarly at risk. 

Even if your waist circumference is below these guidelines, what you eat and how much you exercise are still the keys to health. If you are thin, but don't exercise regularly or follow a healthy eating plan, you can still be at risk for health problems down the road. Measure that belly now and take action to preserve your good health.