Health Risks of Being Underweight
Malnutrition
If you’re underweight, you may not be eating enough healthy foods with key nutrients to fuel your body. That can cause malnutrition.
Symptoms might include:
- feeling tired or drained of energy
- getting sick often or having trouble fighting off illness
- having irregular or skipped periods in females
- experiencing hair thinning or loss, dry skin, or teeth issues
Increased risk of surgical complications
One study found evidence that underweight people who had total knee replacement surgery were more likely to develop infections following the surgery than people who were not underweight. While they could not determine the reasons for this, they believe underweight people aren’t able to heal wounds as well as people with a normal BMI.
Another study found increased complications in underweight people who had total hip replacement surgery compared with people of normal weight. Complications following coronary bypass surgery and lung transplants also seem to be higher for people who are underweight.
Decreased immune function
A recent review of studies found a connection between increased infections and being underweight. The researchers noted their difficulty in determining if this is a result of being underweight or if it has more to do the underlying causes for being underweight. For example, malnourishment may lead to decreased immune function and also cause people to be underweight.
Osteoporosis
Low body weight may increase your risk for low bone mineral density (BMD) and osteoporosis. One study looked at BMD in 1,767 premenopausal women, and found that 24 percent of women with a BMI of 18.5 or lower had a low BMD. Only 9.4 percent of participants with a BMI higher than 18.5 had low BMD.
Infertility
Women with low BMIs are at increased risk for amenorrhea, which is an absence of menses, and other menstrual cycle dysfunctions. Irregular or missed menstrual cycles may be an indicator of anovulation, or that you aren’t ovulating. Chronic anovulation may cause infertility.
Developmental delays
Developmental delays can be seen in underweight children, especially children under the age of 3 when the brain is rapidly developing. The brain needs nutrients to properly develop. Underweight children may be missing key nutrients due to malnutrition and malabsorption. That can impact the development of the brain and lead to delays in developmental milestones.
Health Risks of Being Overweight
The health problems that affect overweight teens include:
- Blount disease: Excess weight on growing bones can lead to this bone deformity of the lower legs.
- Arthritis: Wear and tear on the joints from carrying extra weight can cause this painful joint problem at a young age.
- Asthma: Obesity is associated with breathing problems that can make it harder to keep up with friends, play sports, or just walk from class to class.
- Sleep apnea: This condition (where a person temporarily stops breathing during sleep) is a serious problem for many overweight kids and adults. Not only does it interrupt sleep, sleep apnea can leave people feeling tired and affect their ability to concentrate and learn. It also may lead to heart problems.
- High blood pressure: When blood pressure is high, the heart must pump harder and the arteries must carry blood that's moving under greater pressure. If the problem continues for a long time, the heart and arteries may no longer work as well as they should. High blood pressure, or hypertension, is more common in overweight or obese teens.
- High cholesterol: Long before getting sick, obese teens may have abnormal blood lipid levels, including high cholesterol, low HDL ("good") cholesterol, and high triglyceride levels. These increase the risk of heart attack and stroke when a person gets older.
- Polycystic ovary syndrome (PCOS): Girls who are overweight may miss periods — or not get their periods at all — and might have elevated testosterone (the male hormone) levels in the blood. Although it's normal for girls to have some testosterone in their blood, too much can interfere with normal ovulation and can cause excess hair growth, worsening acne, and male-type baldness. PCOS is associated with insulin resistance, a precursor to developing type 2 diabetes. Overweight women also might have fertility problems.
- Insulin resistance and diabetes: When there is excess body fat, insulin is less effective at getting glucose, the body's main source of energy, into cells. More insulin becomes needed to maintain a normal blood sugar. For some overweight teens, insulin resistance may progress to diabetes (high blood sugar).
- Depression: People who are obese are more likely to be depressed and have lower self-esteem.
Ways to Reach and Maintain a Healthy Weight
Don't skip breakfast: Breakfast kickstarts your metabolism, burning calories from the get-go and giving you energy to do more during the day. People who skip breakfast often feel so hungry that they eat more later on. So they get more calories than they would have if they ate breakfast. In fact, people who skip breakfast tend to have higher BMIs than people who eat breakfast.
Exercise: Regular physical activity burns calories and builds muscle — both of which help you look and feel good and keep weight off.
Reduce screen time: People who spend a lot of time in front of screens are more likely to be overweight. Set reasonable limits on the amount of time you spend watching TV, playing video games, and using computers, phones, and tablets not related to school work.
Watch out for portion distortion: Big portions pile on extra calories that cause weight gain. Sugary beverages, such as sodas, juice drinks, and sports drinks, are empty calories that also contribute to obesity. So choose smaller portions (or share restaurant portions) and go for water or low-fat milk instead of soda.
Eat 5 servings of fruits and veggies a day: Fruits and veggies are about more than just vitamins and minerals. They're also packed with fiber, which means they fill you up. And when you fill up on fruits and veggies, you're less likely to overeat.