A sedentary lifestyle plays a significant role in obesity.  Worldwide there has been a large shift towards less physically demanding work,    and currently at least 30% of the world's population gets insufficient exercise.  This is primarily due to increasing use of mechanized transportation and a greater prevalence of labor-saving technology in the home.    In children, there appear to be declines in levels of physical activity due to less walking and physical education.  World trends in active leisure time physical activity are less clear. The World Health Organization indicates people worldwide are taking up less active recreational pursuits, while a study from Finland  found an increase and a study from the United States found leisure-time physical activity has not changed significantly.  A 2011 review of physical activity in children found that it may not be a significant contributor. 
As a rule, treatment with medicines is not usually used to help children and teenagers lose weight. However, in rare cases, the medicine orlistat may be prescribed to help children aged 12 or over who are severely obese; in particular, if they have started to develop health problems because of their obesity. Orlistat works by interfering with the way that fat is digested and absorbed into the body. If a teenager is prescribed orlistat, this should be under the guidance of a specialist weight loss clinic where overweight and obese children are seen regularly. If prescribed this medicine, the child or teenager will need regular follow-up.