The objective of this quasi-experimental study was to analyze to what extent the loss of weight and subcutaneous fat derived from the application of obesity behavioral programs can be explained by changes in eating habits and physical activity. A sample of 120 obese subjects participated in different obesity behavioral programs (99 women and 21 men; mean age 40 yrs). The person’s weight and the thickness of subcutaneous folds were measured after treatment and after 12 months. The eating habits and physical activity rates of the person were also recorded for these two periods. The results show that changes in eating habits and physical activity account for a high percentage of the variance found in body weight and subcutaneous fat losses. However, the influence of behavioral factors is much greater in the long-term than in the short-term. Clinical and theoretical implications of these and other results are discussed.