I have been opening up as the subject has come up.  Until relatively recently it was just a things between my partner and I, but now as I get fatter, other people are getting wise.
Usually it's in the form of someone commenting on how much I am eating at a single sitting, and I play along by patting my belly and tell them, "Have to make sure this thing doesn't go empty," or something to that effect.
A few friends/neighbours and co-workers have even started encouraging me slightly.  But much like the other posters, none of them really know HOW MUCH I would to gain.  
A few people have made negative comments, or told me I'll have a heart attack or whatever, but those are the exception, and I can laugh them off without concern.
      
      
    10 years