Although it is a popular belief that a reduced level of energy
expenditure and physical activity leads to the development of obesity,
this hypothesis remains controversial and has been difficult to prove.
There are good examples of an inverse relationship between physical
activity and obesity (e.g., athletes are lean, nonobese individuals)21, 48 as
well as good examples of the positive relationship between obesity and
physical inactivity (obese individuals tend to be less physically active).
Not all studies, however, provide supporting evidence. For example,
several studies suggest that increased television viewing (as a marker
for inactivity) increases risk of obesity,’, 21 whereas others do not.40 Similar
to the results for physical activity, some studies suggest that a low level
of energy expenditure predicts the development of obesity, and others
do not support this hypothesis.