Double chin help!

[StinkySaurus]

I’m relatively slim (uk size 12, ocassional 10) but I seem to always have a double chin in photos. Why?! Any tips to avoid?

Theres an exercise in yoga where you push your tongue out and down as far as you can, I think it's called the lion. That is said to help.
And one from Eva Fraser where you put your bottom lip over your top and push your tongue back and under so you tuouch where you tongue joins the floor of your mouth. With your head up. Hold each for a minute or two. Try it for a week or two with before and after pics, they would affect the muscles so the changes will be small but I felt it definitely helped.