By Richard Dobbs, Corinne Sawers, Fraser Thompson, James Manyika, Jonathan Woetzel, Peter Child, Sorcha McKenna, and Angela Spatharou
Box 1. The complex causes of obesity
The root causes of rising obesity are highly complex, spanning evolutionary, biological, psychological, sociological, economic, and institutional factors. The UK government Foresight research on obesity identified more than 100 variables that directly or indirectly affect obesity outcomes (Exhibit 1).
Because of centuries of food insecurity, human beings have evolved with a biological ability to cope with food scarcity rather than abundance. The human body seeks out energy-dense foods and tries to conserve energy as fat. Hormones that regulate hunger and satiety encourage people to seek extra food when food is scarce but do not seem to have the ability to prevent over-consumption or encourage extra calorie burning when food is abundant. Modern life makes fewer physical demands on many people, who lead less active lifestyles as technology replaces the need for physical labor. With many jobs now sedentary, exercise is a conscious and optional choice.
As an illustration of the change, in 1969 about 40 percent of US schoolchildren walked or rode their bikes to school; by 2001, only 13 percent did.1 Over the past 50 years, it has been estimated that a reduction in occupation-related physical activity in the United States has reduced the daily net energy balance by 100 calories per person, a significant share of the overall change in the energy balance during this period.2
Mass urbanization in many regions—the global urban population is growing by 65 million a year, the equivalent of adding seven new cities the size of Chicago every 12 months—is boosting incomes but reinforcing a less physical lifestyle.3 One Chinese study found that urbanization reduces daily energy expenditure by 300 to 400 calories, and traveling to work by car or bus reduces it by a further 200 calories.4
Human beings also have a psychological relationship with food that goes beyond a need for basic sustenance. Many of us use food as a reward or to relieve stress, or have a compulsive relationship with certain types of food. There is a correlation between obesity and high rates of some mental health conditions, including depression. 1 Noreen C. McDonald, “Active transportation to school: Trends among US schoolchildren, 1969–2001,” American Journal of Preventative Medicine, volume 32, issue 6, June 2007.
2 T. S. Church et al., “Trends over 5 decades in US occupation-related physical activity and their associations with obesity,” PLoS ONE, volume 6, number 5, 2011.
3 For more on urbanization, see, for example, Urban world: Mapping the economic power of cities, McKinsey Global Institute, March 2011.
4 W. P. James, “The fundamental drivers of the obesity epidemic,” Obesity Reviews, volume 9, supplement 1, March 2008.
Извор: WUNRN – 22.11.2014
