No one is forcing you! In my group of buddies, one became obese and then invited another obese to join the group.  Here's a short list of my passive aggressive shitlording:  If I have to have any in my car, I crank up the heat.  When I bring snacks, I purposely read the nutritional values for the highest caloric and fat laden ones available.  Once in a blue moon I'll say I'll say I haven't eaten dinner so we'll stop off at Arby's.  Even though the obese already ate dinner, one gets a shake, the other gets Loaded Curly Fries (they have zero shame).  After they order I say I changed my mind, "Nothing sounds good."  If someone brings something like Thin Mints, I'll have just one, even though I might normally have a few, just to make their fat minds explode.  They've ruined our group by making it sedentary and snacking focused.  Screw them.  I've read having fat friends makes you more likely to be a fatty yourself but it has had the opposite effect on me.  Luckily, most of the other guys are skinny to normal.