My gigantic belly in retirement!

So. I am 61. I’m not even full-time retired, I’m part-time since February! Yes, I’m moving around much less. But a good friend told me that I’m fat and I need to lose weight. Is this something that happens in retirement? I’m thinking of even going on those injections, I’ve stepped up my exercise and am watching everything I eat. I tried to post a picture of this so-called belly, but it doesn’t look like our retirement group in Reddit allows it.