Instead of telling people to "eat less", I've found it more productive to focus on other factors that could contribute to obesity and are far less vague and focused on shame. Your suggestion to talk walks and avoid sugar isn't necessarily bad, but it isn't really easy to put into action.

You do have to keep in mind that psychologically, shit's more complicated than just not doing the bad thing.

For example,

"I've found that avoiding anything that's more than 10% sugar is great. Processed foods with way too much sugar in it desensitizes the taste buds too, so now fruits taste much better to me."

"It helped me to sit down and read the ingredients of whatever I was putting into my body."

"Do you live somewhere with forest trails? Something I love doing is walking through them and looking for forage."

The difference is two-fold: It's immediately actionable and easy to envision oneself doing these things and even committing to them, and it's also not being a huge asshole about it in the process.