Obesity is an excessive accumulation of fatty tissue in the body and it is determined based on the body mass index (BMI). Causes of obesity are factors of legacy, environment, lifestyle, and psychosocial factors. Unhealthy lifestyle is a cause of obesity in most people. In most countries, obesity affects 15-30% of the population, and this disorder is slowly becoming pandemic. Prevention of obesity is based on informing and education about the importance of eating healthy and physical activity. As treatment goes, the pharmacological, endoscopic and surgical therapy is used. Depression is a mood disorder or also called, affective disorder. The main symptoms of depression are depressing mood and loss of interest. The stage of depressive episode is classified based on the number of associated symptoms. Causes of depression are biological and psychosocial factors. Depression affects over 300 million people of all ages, but a lot more women than men. Depression treatment is based on a combination of pharmacological and psychotherapy. Pharmacological therapy is based on antidepressants and mood stabilizers. Many epidemiological studies have been carried out on the subject of obesity and depression but the results obtained are not clear and simple. Some studies have come to the conclusion that there is a reverse link between depression and obesity, while others claim that there is no association between depression and body mass index. It is believed that the causes of this relationship are psychological, biological, sociological and cultural factors. Also, the role is played by levels of serotonin, ghrelin, endorphin and noradrenaline. Obesity carries many complications, including depression and it is of great importance to try to prevent it.