5 Health Problems Caused by Being Too Thin

Heart disease and diabetes are usually thought to be problems for the overweight and the obese, but thin people aren't immune from these conditions. It's very easy to be thin yet unhealthy, as naturally thin people might indulge in fast food, skip the gym and think they can get away with it. No matter the number on the scale, though, blood sugar levels and bad cholesterol counts can be rising. Thin people might also skip out on the check-ups that can detect these problems because they think they're in good shape.

Additionally, the very factor that keeps people thin may cause diabetes. People who are naturally very thin are usually that way thanks to genetics, and a 2011 study revealed that these "lean genes" might work by placing fat very deep within the body. Rather than carrying a spare tire, these people might be carrying fat around the heart or the liver. According to the study findings, fat located at these spots might put a person at higher risk for diabetes than visible fat [sources: Naish; Park].

The immune system is like a guard at the gate, ensuring that foreign and abnormal cells do not pass. This system needs fuel to take on invading infections, and unless an underweight person is eating very carefully, he or she could easily starve this disease defense guard. That means that very thin people are at extra risk for getting sick during cold and flu season, and they could be at risk for more serious conditions such as cancer, which begins with abnormal cell activity. If you're very thin, check with a doctor or a nutritionist about dietary supplements that might be necessary to keep you well year-round.

Nutritional deficiencies can also lead to the next problem on our list. What is it?

Many underweight people find themselves feeling tired all the time. This lack of energy and fatigue is a classic symptom of anemia. Other symptoms of anemia include irregular heartbeat, shortness of breath, dizziness and headache. Anemia is a disease of the blood that occurs when there's a deficiency of red blood cells. These blood cells are responsible for transporting oxygen to the organs, and when they don't show up for work, the body doesn't receive the fuel it needs to energize the body. Anemia is caused by nutritional deficiencies of iron, B-12 and folate, which is another reason why underweight people should constantly check with their doctors about whether they're consuming enough of the right foods.

Being underweight can cause many reproductive issues for women. First, a woman's menstrual cycle often stops or becomes irregular when she is too skinny. While that might not matter to a young woman, that irregularity could become an issue when she decides to conceive. Not only is it harder for underweight women to conceive, it's also harder for them to sustain the pregnancy, as menstrual irregularities affect the uterine lining that supports a fetus. According to one study, underweight women who got pregnant were 72 percent more likely to miscarry during the first trimester [source: Naish].

Men aren't off the hook, either -- underweight men are 22 times more at risk for persistent sexual dysfunction such as erectile dysfunction, painful intercourse or inability to ejaculate [source: Goodman]. There may also be a link between a man's weight and the health of his sperm [source: Naish].

While many of us worry about having too much body fat, we all have to have a little bit in order to keep our bodies healthy. One task that fat performs is producing estrogen. We associate estrogen with women, but both men and women need it for healthy bones. Without enough estrogen, bones become brittle and prone to breakage. That leaves both sexes at risk for osteoporosis, no matter their age. As a result, a simple fall or accident is more likely to cause serious injury or even death in an underweight person.

To avoid osteoporosis and the other conditions we've discussed in this article, people who fall below the body mass index of normal weight (18.5) should speak to a medical professional about gaining weight safely. For more on diet, exercise and other health matters, see the links on the next page.