164 Obesity
foods such as fast foods and takeaways. They have identified environ-
mental factors which encourage us to live an increasingly sedentary lifestyle
such as a reduction in manual labor; the use of cars, computers, and televi-
sion; and the design of towns whereby walking is prohibited through the
absence of street lights and pavements and the presence of large distances
between residential areas and places of entertainment or shops. And they
have focused on factors which make it more and more difficult to eat well
and be active such as the presence of lifts and escalators which detract from
stair use and the cheapness of prepared foods which discourage food
shopping and cooking. Accordingly, this obesogenic environment creates
a world in which it is easy to gain weight. Furthermore, the changes in our
environment coincide with the increased prevalence of obesity. From a pub-
lic health perspective, therefore, environmental factors are key to under-
standing obesity, and any attempts to prevent obesity onset should focus
on changing the environment. In line with this, governments provide sub-
sidies for leisure centers trying to make them more accessible for everyone.
There are local campaigns to encourage stair climbing by putting prompts
near lifts and stair wells, and there is legislation limiting food advertising.
Furthermore, some companies encourage their staff to be active in their
lunch breaks by organizing walking groups and offering gym facilities, and
school and work canteens are supported in their attempts to offer healthier
meals. In the same way that many governments have now finally responded
to the knowledge that smoking kills by banning it in public places, steps
are being made to intervene at the environmental and policy levels to
control the obesity epidemic.
From a psychological perspective, however, understanding the environ-
mental factors which promote obesity does not seem to be a sufficient
explanatory model. Psychology focuses on beliefs and behavior, and as
Prentice (1999) argued, “Obesity can only occur when energy intake remains
higher than energy expenditure, for an extended period of time. This is an
incontrovertible cornerstone on which all explanations must be based” (p. 38).
Research has therefore examined the role of behavior in explaining obesity;
behavioral theories of obesity focus on physical activity and eating behavior.
Behavioral TheoriesPhysical activity
Increases in the prevalence of obesity coincide with decreases in daily energy
expenditure due to improvements in transport systems, and a shift from