For most of my life, I've had a real complex about my weight. I'm 5' 4" tall & have rarely weighed less than 12 1/2 stone. And yes, being at the fluffier end of the punting spectrum, I worried about being too heavy for the girls I saw!
I resolved to do something about it when I came home from holiday a couple of years ago. Since then, I've lost 1 1/2 stone and feel so much better about myself, both in my civvy life; and in my punting career, too.
No longer do I worry about being 'too heavy', but because I weigh less, I feel more 'athletic'. To the extent that I now book some girls I'd not normally have considered.
As others have noted, that means I burn off extra calories so it becomes a 'win-win' situation - keeping my weight down.