A 6 year old boy is clinically obese, his BMI >95th centile. He has no other medical problems, examination is unremarkable. His mother says that she has tried everything to help him lose weight. What is the most probable diagnosis?

The key is E. Primary obesity. [People are generally considered obese when their body mass index (BMI) is over 30 kg/m2. Obesity is most commonly caused by a combination of excessive food intake, lack of physical activity, and genetic susceptibility. A few cases are caused primarily by genes, endocrine disorders, medications, or mental disorder].