[voisin]

> Try doing a diet of 500 calories of lettuce and you'll regret it.

Not sure this particular counter example is accurate. The volume of 500 calories of lettuce would be enormous and lead to satiety for other reasons (stretching of stomach).

[xeromal]

I don't think you could pay anyone to eat that much lettuce but it would be easy to pull off with potatoes is more my point.