British Men Think They Are Slim
Brits 'under-estimate waist size'
British men perceive themselves to be an average of 3.1 inches (7.9cm) slimmer around the waist than they really are, research shows.
Ref. https://news.bbc.co.uk/1/hi/health/7262618.stm
This is something that I would agree with, but would put it down to the fact that most British men don't obsess over their weight, unlike many British women.
The majority attending slimming clubs are women, whereas there are only ever the one or two men, sometimes none attending!