Hello, weight gain after training depends on several factors. It s not only age but also genes, type of exercise and least of all food. Let me explain how food affects weight gain. If you re in healthy diet which means that you re taking enough calories from the food and all kind of nutrients then you need no supplements. Supplements may be important in professional athletes but usually make no difference for the casual amateur athlete. The type of exercise is very important. If you re doing low resistance exercise (less than 40%) then you ll get a really nice muscle tone but you won t ever get Schwarzenegger s biceps. If you want to achieve muscular hypertrophy then you need high resistance exercise ( 80%). Since you were exercising for 1.5 hours every day I suppose you did low resistance exercise. I ve left the genes parameter for the end. Two persons doing the same exercises will have different results in muscle hypertrophy. That s because their bodies are different. If you were very muscular in the past then it could be the age thing. If not, then it s most likely the type of exercise. I hope you ve got the answer you were looking for. If you need me to clarify something, I ll be glad to do so. Kind Regards!