The purpose of this study is to examine whether behavioral strategies implemented during the adoption versus the maintenance periods of weight loss to enhance exercise participation in overweight adults are more effective than a standard behavioral intervention.

Inclusion Criteria:

1. Female or Male
2. 18-55 years of age
3. BMI = 25-39.9 kg/m2
4. Ability to provide informed consent.
5. Ability to provide consent from their personal physician to participate in this study.

Exclusion Criteria:

1. Reporting regular exercise participation of at least 20 minutes per day on at least 3 days per week during the previous six months. (This study is designed to recruit relatively sedentary adults.)
2. Diabetes, hypothyroidism, or other medical conditions which would affect energy metabolism.
3. Women who are currently pregnant, pregnant within the previous six months, or planning on becoming pregnant within the next 18 months. (Pregnancy during initial screening will be based on self-report and will be included on the detailed medical history that is completed by subjects)
4. Non-medicated resting systolic blood pressure >160 mmHg or non-medicated resting diastolic blood pressure >100 mmHg, or taking medication that would affect blood pressure.
5. Taking medication that would affect resting heart rate or the heart rate response during exercise (e.g., beta blockade).
6. Arrhythmia on resting or exercise electrocardiogram that would indicate that vigorous exercise was contraindicated.
7. History of myocardial infarction or valvular disease.
8. Weight loss of >5% of body weight within the previous 12 months.
9. History of orthopedic complications that would prevent optimal participation in the exercise component (e.g., heel spurs, severe arthritis).