Identifying Obesity in Children
The same BMI standards used for adults along with anthropometry (measurement of fat by skin fold thickness) may be used to identify overweight adolescents, although there are other considerations in this population. Ethnic variations, timing of growth spurts, and higher normal fat levels around puberty can cause disparities in these measurements.
Causes and Risk Factors for Obesity in Children
Factors Surrounding Birth. The following are some studies reporting certain factors surrounding birth that are associated in a child’s weight:
- Some studies report an association between low birth weight and a risk for later obesity and diabetes. A 2000 UK study proposed that some infants who have a low birth weight due to conditions that restrain growth in the womb (such as having thin mothers who smoke) may undergo a natural catch-up growth between infancy and two years old. This rapid growth, in turn, may increase the risk for later obesity.
- In a study of African American children, having an overweight pregnant mother increased the risk for later weight gain, but low birth weight did not.
- Some studies have found that prolonged and exclusive breast-feeding may offer some protection against childhood obesity.
Socioeconomic and Cultural Factors. Children are particularly vulnerable to the temptations proffered by the media-minded culture, such as food advertisements and sedentary video games. And, neither the media nor even the educational system has strong well-financed programs that encourage healthy alternatives including exercise and healthy foods. The following are some specific problems created by the culture:
- Sugar is a significant problem. (The role of high fat diets on obesity in children is less clear.) Soda, other sweetened beverages, and fruit juice in fact may be singled out as major contributors to childhood obesity. One 2001 study reported that drinking soda regularly increases a child’s risk for obesity by 60%. And the average American adolescent consumes 15 to 20 extra teaspoons a day just from soda and sugary drinks. (Juice, while better than soda, is still filled with sugar.)
- Less physical exercise is playing a significant role in obesity in children. One study has found that the annual distance walked by children has fallen by nearly 30% since 1972, partially because more parents are driving their children to school out of fear of abduction, molestation, and traffic accidents.
- Excessive television watching plays a critical role in obesity in children, particularly in girls and minority children. In one 2001 study obesity rates were lowest in children who watched television one hour or less a day and highest in those who watched four or more hours.
- Studies report that children in low-income families and little mental stimulation have an elevated risk for developing obesity.
Parental Effects. Obesity in parents is a strong risk factor. It is not known if the risk is primarily genetic or environmental.
- When a parent of a child under three is obese, the child, even if thin, has a 30% chance of becoming obese later on.
- Similarly, parental obesity more than doubles the risk that the young child, whether thin or overweight, will become obese as an adult.
- In older children and teenagers, however, obesity in their parents starts to count less as a predictor for body weight than their own weight.
Biologic Effect of Childhood Obesity on Adult Weight
Fat cells change in number or mass depending on a person’s age:
- Fat cells themselves multiply during two growth periods: early childhood and adolescence. Overeating during those times, then, increases the number of fat cells. (Some people are also just born with more fat cells.)
- After adolescence, fat cells tend to increase in mass rather than quantity, so that adults who overeat and gain weight tend to have larger fat cells, not more of them.
Losing weight in adulthood, then, reduces the size of the fat cells but not their number, so weight loss becomes much more difficult for adults who become overweight when fat cells were replicating in childhood. (Such fat-cell growth in adolescence poses a greater risk for being obese in adulthood than in toddlerhood.)
Long-Term Consequences of Childhood Obesity
In one study among overweight children, 77% remained obese into a adulthood, although another study suggested that the risk for persistently high weight was significant only in obese children age 13 and over.
It is not exactly clear if being overweight as a child confers health risks later on if the child achieves normal weight in adulthood. A 2001 study reported that obesity in childhood was not related to any excess health risk. Nevertheless some experts believe that a sudden increase in heart attacks and the rise in type 1 diabetes among young people may be associated with the parallel dramatic increase in obesity. It may also explain the decreasing age for puberty in girls.
Staying overweight or becoming obese in adulthood, in any case, certainly confers health risks. (Of interest was a 2001 study that reported the greatest health risks in obese adults who were very thin children.)
Managing Overweight and Obese Children
Childhood obesity is best treated by a non-drug, multidisciplinary approach including diet, behavior modification, and exercise. Here some tips for children who are overweight:
- Nearly all children snack, which is not itself unhealthy. In fact, if the snacks are healthy eating small frequent meals (instead of two or three large ones) has been associated with being thinner and having a better cholesterol profile. Parents should limit take out, high-sugar snacks, commercial packaged snacks, soda and sugar sweetened beverages (including too much juice), and fast foods in general.
- Parents should not criticize their children for being overweight. Such attitudes could put children at risk for eating disorders, which are equal or even greater dangers to health.
- Simply limiting television, video games, and computer use to a few hours a week can contribute significantly to weight control, regardless of diet and physical activity.
- For young children, try the traffic-light diet. Food is designated with stoplight colors depending on their high caloric content: Green for go (low calories); yellow for “eat with caution” (medium calories); red for “stop” (high calories).
- One 2000 study found that a low-glycemic index diet may be as beneficial and possibly more than a standard reduced-fat diet in obese children. Such a diet focuses on carbohydrates that raise blood sugar more slowly than others. This dietary approach is sometimes used in diabetes.
Revision date: July 5, 2011
Last revised: by Janet A. Staessen, MD, PhD