That'd cost lots more, lead to a load of human rights/abuse/injury claims and not change the behaviour that caused the excessive fat in the first place, so it would be the same people going back every few months/years dpeending on the frequency of checks.

One other thing to remember is that being fat isn't a new phenomenon - if you're from an agricultural background in Ireland and presumably the UK too, a generation or two back 20 stone was considered a good target weight ...

Ratapult?

Here's the all purpose Tom Cruise film script:

Tom Cruise is a [Insert activity/career here]

He's a good [Insert activity/career here] but not the best [Insert activity/career here].

He has a crisis of conscience, meets a woman and becomes the best [Insert activity/career here].

To save anyone spedning the time watching Days of Thunder, Nicole Kidman is pretty hot in it and obviously taller than Cruise when he's not standing on a box out of shot and the only good line in the film is: 'You looked like a monkey f**king a football out there'... 

The most important thing about singlespeed is to make sure to use both gears - sitting and standing...

My local stuff is too steep and variable for me to ever justify building a singlespeed for off road use though - especially if there's a few miles on the road to get there in the first place. My commuting bike and trials bike are singlespeed alright though .