Worldwide there has been a large shift towards less physically demanding work. This has been accompanied by increasing use of mechanized transportation, a greater prevalence of labor saving technology in the home, and less active recreational pursuits. At least 31% of the world’s population does not get sufficient physical exercise. This is true in almost all developed and developing countries, and among children. Some experts refer to sitting as “the new smoking” because of its negative effects on overall health. These exercise trends are contributing to the rising rates of chronic diseases including: obesity, heart disease, stroke and high cholesterol. Active transport (walking, bicycling, etc.) has been found to be inversely related to obesity in Europe, North America, and Australia. Thus exercise has been associated with a decrease in mortality.
One of the causes most prevalent in the developing world is urbanization. As more of the population moves to cities, population over-crowding, increased poverty, increased levels of crime, high-density traffic, low air quality and lack of parks, sidewalks and recreational sports facilities leads to a less active lifestyle. Physical inactivity is increasing or high among many groups in the population including: young people, women, and the elderly. A 2005 population study in south Brazil showed physical inactivity during leisure time to be more prevalent among females and those living with a partner; with a positive correlation associated with age and number of cigarettes smoked, and a negative correlation (decreased levels of physical inactivity) associated with years of formal education, body mass index, and increasing socioeconomic status. Studies in children and adults have found an association between the number of hours of television watched and the prevalence of obesity. A 2008 meta analysis found that 63 of 73 studies (86%) showed an increased rate of childhood obesity with increased media exposure, and rates increasing proportionally to time spent watching television. Another cause in the case of children is that physical activity in activities from self-propelled transport, to school physical education, and organized sports is declining in many countries.
Noncommunicable diseases, partly due to a lack of exercise, are currently the greatest public health problem in most countries around the world. Each year at least 1.9 million people die as a result of physical inactivity, which makes inactivity one of the leading preventable causes of death worldwide.
Australian children between 1961 and 2002 have had a marked decline in their aerobic fitness.
Obese people are less active than their normal weight counterparts. In Canada, 27.0% of sedentary men are obese as opposed to 19.6% of active men. Lean people are more fidgety than their obese counterparts; this relationship is maintained even if normal weight people eat more or the obese person loses weight. National data indicates that only 10% of Canadian youth are meeting the guideline for screen time of less than 2 hours per day. As well, although 2/3 of families live close enough for their children to bike or walk to school, only 1/3 report actually walking to school and 80% report never having cycled to school.
A study from China found urbanization reduced daily energy expenditure by about 300–400 kcal and going to work by car or bus reduced it by a further 200 kcal. A rapid decline in physical activity has occurred between the 1980s and the 2000s. The decline in physical activity is attributed to increasing technology in the workplace and changing leisure activities. In 1989 65% of Chinese had jobs that required heavy labor. This decreased to 51% in the year 2000. Among Asian children between 1917 and 2003 little change has been seen in power and speed however endurance has decreased substantially in the last 10–15 years.
In Finland leisure-time physical activity has increased, while occupational and commuting physical activity has decreased from 1972 to 2002. Leisure-time physical activity increased from 66% (1972) to 77% (2002) in men and from 49% (1972)to 76% (2002) in women. Physically demanding work decreased from 60% (1972) to 38% (2002) in men and from 47% (1972) to 25% (2002) in women. Daily commuting activity decreased from 30% (1972) to 10% (2002) in men and from 34% (1972) to 22% (2002) in women.