There are two sides to this.

Yes, they appear hypocritical but may feel embarrassed that they couldn't express themselves better in your company (I'm including the group chat here).

My sister-in-law often ruined many family meals by her evangelical attitude to weight loss. I know some of it was directed to me. Yes, I'm about a stone overweight (typical post menopause!). Her reason was hypocritical; she wanted to eat healthily so she could consume more alcohol. Then, she wondered why her weight loss had stopped!

There are other reasons why people gain weight, it's not just about poor diet and lack of exercise. Of course, fat shamers and those seeking to profit from our desire to be thinner don't mention that.