Obesity Treatment 193experimental study to evaluate the effect of manipulating exercise levels on
depression. Forty-three female students who scored higher than the cutoff
point on the Beck Depression Inventory (BDI) were randomly allocated to
one of three groups: 1) an aerobic exercise group (one hour of exercise, twice
a week for 10 weeks), 2) a placebo group (relaxation), and 3) no treatment.
After 5 weeks, the results showed a significant reduction in depressive symp-
tomatology in the exercise group compared with the other two subject groups,
supporting the relationship between exercise and depression and suggesting
a causal link between these two variables, that is, increased exercise resulted
in a reduction in depression. However, the authors report that subsequent
exercise had no further effects. Hall et al. (2002) also used an experimental
design to explore the relationship between exercise and affect with 30 volun-
teers rating their affective state every minute as they ran on a treadmill.
The results showed improvements in affect from baseline to follow-up which
supports previous research suggesting that exercise is beneficial. However,
the results also showed a brief deterioration in mood midexercise. The authors
suggested that although prolonged exercise may improve mood, this dip
in mood may explain why people fail to adhere to exercise programs.
Figure 9.2 Mortality and fitness level in individuals with a BMI >25.4.
(Source: S.N. Blair, Evidence for success of exercise in weight loss and control,
Annals of Internal Medicine, 199 (1993), pp. 702 – 6.)
Image not available in the electronic edition