I also happen to have a relatively small penis. I want to know if losing weight will change anything in terms of my endowment. What it will do is give your genitals more room as they will be more easily seen, giving them a larger appearance. Also, losing weight will lead to a healthier lifestyle and allow all aspects of your body to function better, including your erections.
Many men claim to have gotten stronger and firmer erections after losing weight.
This may also have to do with the added muscle and athleticism of the individual. If you are not having problems with your urination, erectile function and ejaculation, then you shouldn't be worried. You should be concerned with your weight for other reasons than your penis size. Maintaining a healthy diet and lifestyle will improve many aspects of your life and might even lead to you becoming less concerned with your size. It takes me so long to ejaculate that I often cannot finish because my wife is sore and tired.