Physical inactivity of children has also shown to be a serious cause, and children who fail to engage in regular physical activity are at greater risk of obesity. Researchers studied the physical activity of 133 children over a three week period using an accelerometer to measure each child's level of physical activity. They discovered the obese children were 35% less active on school days and 65% less active on weekends compared to non-obese children.
Physical inactivity as a child could result in physical inactivity as an adult. In a fitness survey of 6,000 adults, researchers discovered that 25% of those who were considered active at ages 14 to 19 were also active adults, compared to 2% of those who were inactive at ages 14 to 19, who were now said to be active adults. Staying physically inactive leaves unused energy in the body, most of which is stored as fat. Researchers studied 16 men over a 14 day period and fed them 50% more of their energy required every day through fats and carbohydrates. They discovered that carbohydrate overfeeding produced 75–85% excess energy being stored as body fat and fat overfeeding produced 90–95% storage of excess energy as body fat.
Many children fail to exercise because they are spending time doing stationary activities such as playing video games or watching TV. TV and other technology may be large factors of physically inactive children. Researchers provided a technology questionnaire to 4,561 children, ages 14, 16, and 18. They discovered children were 21.5% more likely to be overweight when watching 4+ hours of TV per day, 4.5% more likely to be overweight when using a computer one or more hours per day, and unaffected by potential weight gain from playing video games. A randomized trial showed that reducing television viewing and computer use can decrease age-adjusted BMI; reduced calorie intake was thought to be the greatest contributor to the BMI decrease.
Technological activities are not the only household influences of childhood obesity. Low-income households can affect a child's tendency to gain weight. Over a three week period researchers studied the relationship of socioeconomic status (SES) to body composition in 194 children, ages 11–12. They measured weight, waist girth, stretch stature, skin folds, physical activity, TV viewing, and SES; researchers discovered clear SES inclines to upper class children compared to the lower class children.