Childhood obesity in the U.S. is growing at an alarming rate. According to the U.S. Centers for Disease Control and Prevention (CDC), the obesity rate among U.S. children and teens has more than tripled since 1980. Obesity is a complex disease with many causes. Some causes of obesity in children include nutrition and eating patterns, physical activity levels, insufficient sleep, genetics, and emotional stress. The conditions in which the child lives, learns, and plays can also cause obesity. In some cases, a child may have obesity because of a specific illness or medicine.

Obesity is defined as a BMI (body mass index) at or above the 95th percentile for children of the same sex and age. Overweight is defined as a BMI at or above the 85th percentile but less than the 95th percentile. Healthy weight is defined as a BMI at or above the 5th percentile to less than the 85th percentile.

These percentiles are based on CDC growth charts for children and teens ages 2 through 19. For children and teens, BMI is age- and sex-specific. It's often called BMI-for-age. A single BMI calculation is not enough to determine long-term weight status. This is because your child's height and weight will continue to change as they grow. Your child's doctor will use BMI along with other factors to determine weight status. These other factors are family history, blood pressure, blood sugar levels, eating patterns, and physical activity level. You can calculate your child's BMI.

Children who take in too many calories and don't get enough exercise or sleep are at risk for obesity. Some children may have only limited access to healthy foods like fruits and vegetables. This includes children who live in lower-income neighborhoods. Many children don't get enough physical activity. This is because more children are watching TV, playing video games, or doing other screen-time activities.

To help combat these factors, parents can make these positive changes in kids' lives:

• Move more as a family. Children ages 3 through 5 should be physically active throughout the day. This includes active play like tricycle-riding and skipping. Children ages 6 through 17 need at least 60 minutes of medium- to high-intensity physical activity every day. This can include fun aerobic activities like playing tag and jumping rope. Set a positive example for your children by being active yourself. Make exercise a part of your daily routine. Try taking a family walk, dancing, biking, or playing an outdoor game together as often as you can.
• Set regular sleep routines. Good sleep helps prevent diseases. These include type 2 diabetes and obesity, injuries, and problems with attention and behavior. Children who don't get enough sleep are at risk for unhealthy weight gain. Remove screens from your child's room. Stop the use of screens at least 1 hour before bedtime. Follow a consistent sleep schedule, even on the weekends. This can help children sleep better.
• Model a healthy eating plan. Following a healthier diet as a family can help children reach and stay at a weight that is healthy for them. Healthy and nutritious foods include a variety of vegetables and fruits, whole grains, lean protein foods, and low-fat and fat-free dairy products. Keep soda and chips out of the house. Or have them only on very special occasions. Try serving your children kid-friendly snacks. These include fruit smoothies, raw veggies with yogurt dip, and celery with peanut butter. If fresh produce isn't available or costs too much, look for frozen choices.
• Watch portion sizes. Over the past few decades, portions of foods in both grocery stores and restaurants have ballooned. Make sure the amount of food your children eat stays within the USDA advice for meal sizes for each food group. For example, 1 serving of grains is just a half-cup of spaghetti or one regular slice of bread. Half a small chicken breast and a small, lean hamburger patty each count as 1 serving of protein.
• Limit screen time. Too much screen time can lead to poor sleep, weight gain, lower grades in school, and poor mental health in children. The American Academy of Pediatrics recommends creating a family media plan to help your family set media priorities. This kind of plan makes sure that health, academic, and social goals are met first. Then media use time is addressed. You can use the the AAP site to develop your own family media plan.
• Focus on health, not body appearance. Blame and guilt about a body shape or size is not helpful. It is often harmful and can affect the success of treatment. Similar to the treatment of other chronic diseases such as asthma, obesity treatment should focus on overall health and quality of life. For example, treatment goals may include improving self-esteem, missing less school, and taking part in events such as a walkathon.

Some children reach a weight that is higher than what is healthy for them or they have obesity because of certain illnesses or inherited problems. Talk with your child's doctor if you have concerns about a medical cause of increased weight gain. Some examples include:

• Prader-Willi syndrome. This inherited disease can cause feelings of hunger that can't be controlled and a metabolism that burns fewer calories than normal. Other symptoms of the condition include low levels of sex hormones and poor muscle tone. The condition has no cure, but early diagnosis can help parents take steps to prevent their children from having obesity.
• Cushing syndrome. This disease most often affects adults between ages 20 and 50. But it can happen in children. In children with Cushing syndrome, growth rate slows, but the rate of weight gain increases. Cushing syndrome is marked by a moon face, acne, easily bruised skin, stretch marks, and fatigue or depression. It's caused by prolonged exposure to cortisol, a stress-related hormone in the body. The extra cortisol can be released because of tumors on the adrenal glands or pituitary gland or from overuse of steroid medicines. Depending on the cause of this disease, surgery, radiation, chemotherapy, and medicines can all be used to treat Cushing syndrome. If you suspect your child may have the condition, talk with your child's doctor.
• Hypothyroidism. This is a condition caused by low activity in the thyroid gland. This controls how quickly the body burns calories. Children with hypothyroidism may be slow to grow and have delayed development. It's less common than delayed growth and short stature in children, but many children with hypothyroidism have weight gain. They may also have pale skin and feel tired. Medicines to restore normal thyroid hormone levels can help treat hypothyroidism. Your child's doctor can do tests to screen for this condition.

Some children reach a weight that is higher than what is healthy for them or they have obesity because of certain medicines they take. Talk with your child's doctor if you have concerns about a medicine cause of increased weight gain. Some examples include:

• Antidepressants.
• Steroids.
• Birth control, including injected forms.
• Medicine used in children with diabetes.
• Medicines for psychosis.
• Medicines for seizures.