Can Parkinson's disease affect your metabolism and is it hereditary?

Yes!! Pd can definitely cause fatigue/malaise, even out-right excessive daytime sleepiness. These are purely organic symptoms of the disease. Also, slowed gut parastalsis can reduce appetite (loss of sense of smell & thereby taste contributes too) , cause early satiety (filling quickly), constipation & leave the person feeling gassy & bloated. All of which contribute to a sense slow metabolism.