Hello, if you believe that this weight gain cannot be adequately justified by your lifestyle and eating habits then you should let your primary care physician assess your health both with clinical examination and with laboratory tests. This assessment should definitely exclude hypothyroidism (a serum TSH measurement is usually sufficient to exclude it). Other potential causes may include liver cirrhosis with fluid accumulation in the abdomen (ascites). Liver problems cannot justify the thigh enlargement though and we would expect other symptoms and signs as well. Sex hormones may play some role in males. Drugs may affect your appetite and how easy you may gain weight. All of the aforementioned factors - and perhaps other factors too, that may apply to you - should be taken into account by your doctor. Accompanying symptoms are useful in this regard - if there are any! On the other hand, it s a fact that we gain weight as we grow (300-500gr each year after the age of 30). Some people gain weight in the stomach, others in the thighs or other areas - genes determine body fat distribution. So in conclusion, hypothyroidism is the first potential disorder that has to be excluded. You should visit your PCP for further investigation. I hope I ve answered your question. Please let me know if you need further assistance. Kind Regards, Dr Panagiotis Zografakis Internal Medicine Specialist