In the present study, the MMPI was used to detect personality changes in 53 overweight, yet otherwise healthy, males who were participating in either a weight reduction or an aerobic exercise conditioning program. Analysis of pre- and post-intervention scores revealed that only the participants in the aerobic conditioning group demonstrated the predicted desirable psychological changes. More specifically, this group displayed significant clinically desirable changes on the Hs, PD, and HEA scores. Similar to the weight loss participants, a demographically matched nonintervention comparison group showed none of these desirable changes and actually yielded a significant increase on the D scale. However, when compared to this "normal" group, both intervention programs showed statistically significant differences on at least two MMPI scales.