When children eat more than they need, their bodies store the extra calories in fat cells to use for energy later. If their bodies do not need this stored energy, they develop more fat cells and may become obese.
No single factor or behavior causes obesity. Obesity is caused by many things, including a person’s habits, lifestyle, and environment. Genes and some medical problems also increase a person's chances of becoming obese.
Learned Behaviors and Habits
Infants and young children are very good at listening to their bodies' signals of hunger and fullness. They will stop eating as soon as their bodies tell them they have had enough. But sometimes a well-meaning parent tells them they have to finish everything on their plate. This forces them to ignore their fullness and eat everything that is served to them.
The way we eat when we are children may strongly affect our eating behaviors as adults. When we repeat these behaviors over many years, they become habits. They affect what we eat, when we eat, and how much we eat.
Other learned behaviors include using food to:
Reward good behaviors
Seek comfort when we feel sad
These learned habits lead to eating no matter if we are hungry or full. Many people have a very hard time breaking these habits
Lifestyle and Environment
The family, friends, schools, and community resources in a child's environment reinforce lifestyle habits regarding diet and activity.
Children are surrounded by many things that make it easy to overeat and harder to be active:
Parents have less time to plan and prepare healthy meals. As a result, children are eating more processed and fast foods that are usually less healthy than home-cooked meals.
More foods today are processed and high in fat and contain too much sugar.
Vending machines and convenience stores make it easy to get a quick snack, but they rarely sell healthy foods.
Overeating is a habit that is reinforced by restaurants that advertise high-calorie foods and large portion sizes.
If a parent is overweight and has poor diet and exercise habits, the child is likely to adopt the same habits.
Screen time, such as watching television, gaming, texting, and playing on the computer are activities that require very little energy. They take up a lot of time and replace physical activity. And, when children watch TV, they often crave the unhealthy high-calorie snacks they see on commercials.
Schools have an important role in teaching students about healthy food choices and exercise. Many schools now limit unhealthy foods in lunches and vending machines. They are also encouraging students to exercise more.
In the Community
Having a safe community that supports outdoor activities at parks, or indoor activities at community centers, is important for encouraging physical activity. If a parent feels it is not safe to allow their child to play outside, the child is more likely to do sedentary activities inside.
Eating Disorders and Obesity in Children
The term "eating disorders" refers to a group of medical problems that have an unhealthy focus on eating, dieting, losing or gaining weight, and body image. Examples of eating disorders are:
Obesity and eating disorders often occur at the same time in teens and young adults who may be unhappy with their body image.
Some children are at greater risk of obesity because of genetic factors. They have inherited genes from their parents that make their bodies gain weight easily. This would have been a very good trait hundreds of years ago, when food was hard to find and people were very active. Today, though, this can work against people who have these genes.
Genetics is not the only cause of obesity. To become obese, children must also eat more calories than they need for growth and energy.
Certain medical conditions can increase a child's appetite. These include hormone disorders or low thyroid function, and certain medicines, such as steroids or anti-seizure medications. Over time, any of these can increase the risk of obesity.
Gahagan S. Overweight and obesity. In: Kliegman RM, Stanton BF, St. Geme JW III, et al., eds. Nelson Textbook of Pediatrics. 19th ed. Philadelphia, PA: Elsevier Saunders; 2011:chap 44.
US Department of Agriculture Food and Nutrition Service. Healthier school day. Available at: www.fns.usda.gov/healthierschoolday/tools-schools-smart-snacks. Accessed August 30, 2014.
US Preventive Services Task Force. Screening for obesity in children and adolescents: US Preventive Services Task Force recommendation statement. Pediatrics. 2010;125:361-367. PMID: 20083515 www.ncbi.nlm.nih.gov/pubmed/20083515.
Neil K. Kaneshiro, MD, MHA, Clinical Assistant Professor of Pediatrics, University of Washington School of Medicine, Seattle, WA. Also reviewed by David Zieve, MD, MHA, Isla Ogilvie, PhD, and the A.D.A.M. Editorial team.