An analysis of over 2000 child-hours (time spent for observation of children in the study) of systematic direct observations showed that children in preschool were engaged in Moderate-to-Vigorous-Activity (MVPA) for only 2% of the observation intervals. These children were sedentary or very lightly active for over 85% of the observation periods.

A continuing study indicates that children ages 4-5 are already more sedentary than 3-year old children.

Middle childhood, defined chronologically as 5-9 years of age, is an important transition period for activity behaviors, since children move from the comparatively unscheduled time of early childhood to the discipline of the school environment. Normally, children will develop and enhance their locomotor skills in this period, including running, skipping, bicycling, throwing, catching, etc.

Unfortunately, studies show that children's activity levels continue to decline, even during this crucial period of 5-9 years of age.

The situation worsens as children enter middle and high school age. Activity studies show that children ages 10 to 16 spend over 10 hours each day sedentary. These children spend only 12 to 13 minutes per day engaged in vigorous physical activity. This data also demonstrates a significant decline in physical activity as children progress through adolescence, particularly in girls whose activity levels drop significantly after the age of 10.

Balance between energy intake and expenditure is critical for maintaining weight and preventing excessive weight gain. It takes a relatively small increase in calories to produce an increase in weight. The 12 pound increase in median weight for adult men between 1971 and 1994 could have been generated by a mere 155 extra calories per day, the equivalent of a 12-ounce can of soda, if there was no extra change in activity to burn off those additional calories.

This disturbance in energy-balance is exacerbated by the prevalence of fast-foods and high-calorie foods. These foods appeal to basic palatability preferences for sugar and fats. A large fast-food meal can easily contain 2,200 calories, which would take a full marathon to expend (assuming a burn rate of 85-100 calories per mile). Fast-food had gone from contributing 2% of a children's total calories to about 10% in the late 1990s. A 2003-2004 study showed that 30-40% of children reported eating fast-food on a daily basis.

Children's consumption of various forms of multimedia constitutes a large portion of time spent on sedentary activity.

Nearly one quarter of American children have 4 or more televisions in their homes, and on average, American children spend almost as much time per week watching television (25 hours) as they spend in school.

A 9-month observation of 250 3-10 year-old children demonstrated that as little as 2.6 hours per day of television viewing caused numerous problems, including weight-gain, decrease in physical activity, decreased interest in study, decreased school performance, and sleep pattern disturbances. Medical problems were found in 11.6% of the children.

Research suggests that children's preferences for food are influenced by advertising. Well over half of all TV commercials are for edible products, the majority of which are for non-nutritious foods.

There is a direct correspondence between the time spent in front of the television and increased BMI among US youth. Repeated exposure to television commercial for food tend to prompt children to increase their food consumption, resulting in even greater weight-gain.

Children watch an average 11,000 low-nutrition "junk" food ads per year on TV, and often, in stores, request foods that are highly advertised. These ads seem to affect boys more than girls. So far, pro-nutrition ads have proven not to be very effective in increasing the consumption of nutritious foods.

A recent survey found that 53% of people reported that they most often snacked in front of the television. One study of about 1000 individuals found that every additional hour of TV per day was associated with 50-136 additional calories consumed.

Increased accessibility of multimedia devices has drastically changed people's leisure preferences. About 30% of people report that they engage in no physical activity during their leisure time. One study demonstrated that lower amounts of leisure-based screen time resulted in increased amounts of physical activity in 5-12-year-olds. Those who watched more TV during their leisure hours participated in significantly fewer hours of physical activity.

One study which measured multimedia habits in students shows that the average high school graduate will likely spend 15,000 to 18,000 hours watching television, but only 12,000 hours in school. Next to sleeping, television-watching makes up the greatest amount of leisure-time.

This sedentary lifestyle has spread further, even into transportation habits of people. Americans walk less and drive more - even for trips of less than one mile. Workplace activity levels have dropped due to increased automation from technological advances.

This trend of inactivity and subsequent overweight and obesity appear to be strongly connected to the Western lifestyle. As more countries adopt the comforts of technology and inactive lifestyle, they become afflicted with the same diseases stemming from inactivity.

A World Health Organization (WHO) report estimates that 1.9 million deaths worldwide are attributable to physical inactivity. The same report estimated that less than one-third of young people are sufficiently active to benefit their present and future health and well-being.

Many studies confirm that even a modest increase in physical activity, only 15 minutes of Moderate to Vigorous Physical Activity (MVPA) is associate with lower odds of obesity of around 50% in boys, and around 40% in girls. Such a small change in lifestyle plays an important role in preventing many chronic diseases such as heart disease, hypertension, and type 2 diabetes.

An extensive population study showed that children engaged in vigorous physical activity from late childhood to adolescence were only 40% as likely to have weight problems in the future, when compared to their sedentary peers. This suggests that activity levels in childhood are strongly linked to activity levels later in life.

One study involving 8 primrary schools showed that increases in physical activity alone, even implemented over just 10 months, was effective in reducing BMI, wasit circumference, and estimated body fat percentage.