Gary Becker, Nobel Laureate in economics, explains why we are getting fatter:
Several factors explain why the average weight of Americans (and those in other developed countries) increased a lot more rapidly after 1980 than it had before. The effective price of fatty foods began to decline rapidly at that time, in part due to the growth of fast food chains, like McDonald’s. Also important, especially for teenagers, is the attraction of sedentary activities resulting from computers, email and instant messaging, and video games that replaced time at sports and other more physically challenging activities. (Television viewing by Americans did not increase, and may have declined, during the past 25 years.) The development of many drugs that combat high blood pressure, high cholesterol levels, and other ill health caused by being greatly overweight, and a reasonable expectation of further medical progress in the future, also contributed to the declining concern about being greatly overweight.