<human>: M and I have been mates for at least 15 years. He plays a lot of indoor sport and comes off the court smelling pretty nasty. However he's always just been a sweaty guy. 
  
My other friends and I (who are all good friends with him) noticed it ages ago. That he has a certain pong to him. Because none of us directly and maturely dealt with is straight up when we first noticed it, we're somewhat stuck with it. 
  
Fast forward to a few weeks ago. I bring my friend over to another friend (D)'s place to watch sport. M 32 and I are sitting on one couch, the others are on another couch.   M is wearing jeans and a singlet. 

My friend D who was hosting us, tells me later that M has a body odor problem and was stinking out the house. He and his other mates were overwhelmed with the stench. He also had to text to warn the next people coming over (so as to not offend my friend by asking "what's that smell?" when they arrived). 
 
D brings all this up a couple weeks afterwards when we're hanging again. He had to wash his couch cushions and air out the house for the next day as it was so bad. He asked if I knew about the issue. I told him I did. He is a friend who calls a spade a spade, and is direct with all his friends. He told me I need to say something (which I agree with). 
  
My question is not, do I say something? It is, how to I delicately but in an adult way tell my friend M (lovingly) that he has a BO problem and it affects those people we all hang out with.  I know that there are medical options to treat such a problem, but right now doing nothing affects me and the people I hang with!

Can you provide a brief overview of the text?
<bot>: Friend has had BO problems for years and no-one has directly confronted him about it. Now it's affecting me and those I hang with. How do I tell him in a way that isn't offensive but is supportive and constructive?