In recent years, excessive body weight has become one of the most serious psychological, biological and social problems. According to forecasts by the World Health Organization, obesity and overweight will continue to increase among both adults and children in the coming years. Poland ranks sixth in Europe in this respect. In 2021, almost 58% of Poles had above-average body weight (overweight or obesity). In Poland, 29% of women are overweight, and 21% of women are obese. Body dissatisfaction, depression, and anxiety disorder are indicated as consequences of high BMI in women. Reducing excess body weight improves psychosocial functioning and changes body assessment. The most lasting effects of weight reduction are achieved by a properly selected diet combined with increased physical activity. This results in a change in lifestyle, changes in the levels of metabolic indicators, and changes in one’s body image and mental health. Objective: Our objective was to assess changes in body image and mental health among Polish women and their dependence on the weight reduction method used (type of diet and physical activity). Comparative studies involving 122 women were conducted. These women were selected from 1000 volunteers based on BMI criteria. The effects of diet therapy were compared with the effects of diet therapy combined with physical activity. Research tools: The GHQ-12 scale was used to measure mental health, and the Body Esteem Scale was used to measure body image. The study lasted four years. The results showed changes in body image, general mental health index, and BMI in women who dieted and in those who dieted and exercised. In women using a diet combined with physical activity, greater positive changes in mental condition and stronger positive changes in body image, namely in the assessment of satisfaction with sexual attractiveness, physical condition, and body weight control, were observed compared to women using diet therapy alone.