In our looks-obsessed society, many people think that being overweight is an appearance issue. But being overweight can be a medical concern because it can seriously affect a person's health.

Doctors use the medical terms "overweight" or "obese" to tell if someone has a greater chance of developing weight-related health problems.

Why Do People Become Overweight?

When people eat more calories than they use, their bodies store the extra calories as fat. A couple pounds of extra body fat usually doesn’t cause problems for most people. But when people keep up a pattern of eating more calories than they burn, more and more fat builds up in their bodies.

Weight problems tends to run in families. Some people have a genetic tendency to gain weight more easily than others. Although genes strongly influence body type and size, the environment also plays a role.

People today are gaining weight because of unhealthy food choices (like fast food) and family habits (like eating in front of the TV instead of around a table). High-calorie, low-nutrient snacks (like chips, cookies, and ice cream) and beverages (like soda, juice, and sports drinks), bigger portions of food, and less-active lifestyles are all contributing to the obesity epidemic. And people who don’t get enough sleep are more likely to be overweight.

Sometimes people turn to food for emotional reasons, such as when they feel upset, anxious, sad, stressed out, or even bored. When this happens, they often eat more than they need.

Defining Overweight

Figuring out if a teen is overweight is a little more complicated than it is for adults. That's because teens are still growing and developing.

Doctors and other health care professionals use a measurement called body mass index (BMI) to tell if someone is overweight.

The doctor calculates BMI using a person's height and weight, and then plots that number on a chart to see what weight category they are in. There are different charts for girls or guys. BMI estimates how much body fat the person has. People with high BMI are more likely to have weight-related health problems.

Doctors use four categories to describe a person's weight:

• Underweight: A person weighs less than the healthy range for their age, gender, and height.
• Healthy weight: A person's weight is in the healthy range for their age, gender, and height.
• Overweight: A person weighs more than the healthy range for their age, gender, and height.
• Obese: A person weighs much more than the healthy range for their age, gender, and height.

Because muscle weighs more than fat, a muscular person can have a high BMI, but not too much body fat. Likewise, it's possible for someone to have a low or ideal BMI but still have too much body fat.

You may get a BMI report from school, but the best way to understand BMI is to talk to your doctor.

Health Problems of Being Overweight

Weight-related health problems include:

Asthma. Obesity increases the chance of having asthma. Breathing problems related to weight 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. Sleep apnea can leave people feeling tired and having trouble paying attention and learning. It also may lead to heart problems.

High blood pressure. When blood pressure is high, the heart has to work harder. If the problem continues for a long time, high blood pressure can damage the heart and arteries.

High cholesterol. Abnormal blood lipid levels, including high cholesterol, low HDL ("good") cholesterol, and high triglyceride levels, increase the chances of having a heart attack or stroke when a person gets older.

Gallstones. A buildup of bile that hardens in the gallbladder forms gallstones. These can be painful and require surgery.

Fatty liver. If fat builds up in the liver, it can cause inflammation, scarring, and permanent liver damage.

Joint and muscle pain. Wear and tear on the joints from carrying extra weight can cause pain and may lead to arthritis in adulthood.

Slipped capital femoral epiphyses (SCFE). SCFE is a painful hip problem that requires immediate attention and surgery to prevent further damage to the joint.

Pseudotumor cerebri. This is a rare cause of severe headaches in obese teens and adults. There is no tumor, but pressure builds in the brain. Besides headaches, symptoms may include vomiting, double vision, and other vision problems.

Polycystic ovary syndrome (PCOS). Although it's normal for girls to have some testosterone (the male hormone), girls with PCOS have higher testosterone levels in the blood. This leads to irregular periods, too much hair growth, and bad acne.

Insulin resistance and diabetes. Insulin is a hormone that lowers the level of glucose (a type of sugar) in the blood. When there is too much body fat, insulin doesn’t work as well getting glucose, the body's main source of energy, into cells. The body then needs more insulin to keep a normal blood sugar level. For some overweight teens, insulin resistance can progress to prediabetes and diabetes (high blood sugar).

Depression. People with weight problems are more likely to be depressed and have lower self-esteem.

Luckily, it's never too late to make changes that can help control weight gain and the health problems it causes. Those changes don't have to be big. For a start, make a plan to cut back on sugary beverages, control portions, and get more exercise, even if it's just 5–10 minutes a day. Build your way up to big changes by making a series of small ones. And don't be afraid to ask for help!