I suppose the way to go is to talk about BMI in direct relation to standard height and weight measurements.
Rather than giving the impression you noticed they look fat.
I think the thing is tho that most people who are overweight know it and know it’s bad for their health. I think there’s a basic misunderstanding about the psychology at play and why people struggle to lose weight.
(Besides the fact – currently being demonstrated by Zoe and the data they’re amassing – that different people process different types of foods differently. I can and do eat cheese, butter and cream all day and it doesn’t impact my weight at all.)
From my own experience: I’m naturally on the skinny side (not a boast, just one of those things) and hated this at school as a teen, so never developed worries about weight gain and never really bothered about putting on a bit of weight or having a little pot belly (at a healthy BMI).
Then at one point in my early 20s I put on I don’t know – maybe half a stone or a stone (was living with a basketball player and sharing a junk food diet). So not a -massive- amount by any standard. The difference this time was that a family member kept on and on at me and made me feel really shitty about it. This weird thing then happened where I started eating compulsively. I’ve never felt the same before or since, but there was this few months where I felt bad for having put on weight (I was still a completely normal size, small even – maybe a size 12! FS…) yet would eat more than I ever had before while zoning out from these feelings of guilt. It was so odd and left a lasting impression. I’m just so sure that feeling ashamed, judged and fearful about your weight doesn’t help anyone lose it.
Maybe focusing on the health benefits of something like weight lifting would be a better approach? I think people respond better when they feel positive and virtuous about something than shamed and guilty.
Just my tuppence worth.