Burke et al65 conducted a meta-analysis and
reported medium effect sizes for MI interventions
for diet and exercise problem behaviors. A more
recent meta-analysis of 72 randomized controlled
studies, assessing the effectiveness of MI on such
outcomes as blood cholesterol and blood pressure,
found a significant effect in 74% of the trials.66 MI
outperformed traditional advice-giving in about
80% of the studies. MI was designed to assist
behavior change through brief encounters of only
15 minutes. There is reason to believe that MI has
the potential to demonstrate a dose-response relationship
66 and the extended contact with CR participants
may reveal even greater effect sizes. MI might
be particularly effective in increasing physical activity
and healthy eating in women with CHD because
these behaviors do not involve a physiological
addiction that may complicate the change process.