If it were me, I would just explain nicely that thank you for your concerns and comments but right now these comments are unhelpful as you need to put all of your energy towards your battle, and worrying about the small things, is unhelpful. Tell them you have a TEAM of medical staff checking up on nearly all aspects of your life at present and watching your weight, and food intake and making sure your rest etc. that they have given you all the information on the balance of rest vs activity and eating etc etc. And that while you appreciate there concern, by getting this information from others as well it is sending you into information overload and you are worried that you might miss some important information from your medical team, becasue of this.
That is what I told my family and friends.
Hope this helps.