Inclusion Criteria:  Men aged between 18 and 60 years Unfulfilled desire to have a child > 1 year reduced sperm quality (proven via spermiogram according tho WHO-5 criteria) informed consent 20 kg/m² <= BMI <= 35 kg/m²  Exclusion Criteria:  No sufficient communication possible severely impairing cognitive illness serious mental illness Patients with anatomical/organic damage of reproductive organs Eating disorders in the medical history Serious internal diseases Lack of internet access No consent to randomisation Participation in other studies