If lost some sensitivity in my penis during sex. i'm wondering if it's the weight gainer i'm taking or something in my diet affecting me.

Did it return?: I would say likely nothing to do with your diet. Did it last or resolve after intercourse? again, likely not to do w diet.

Here are some…: According to the information known to us, there has been no such connection between weight-enhancing diet and changing penile sensation during intercourse. At 43, it's reasonable to look into the other healthy issues or drug use / abuse which might be suspected to be related with changing sexual function. So, sick professional evaluation and counseling timely. Best wish…

Loss of sensitivity: in any part of the body needs to be examined by a doc. Your family doc may refer you to a urologist. If no medical cause is found you can consult a licensed sex therapist or other mental health professional. I suggest not taking the weight gainer if it is over the counter and see a nutritionist. Peace and good health.