I found this fascinating piece on the amount of weight to gained by a British football fan watching the 2010 Soccer World cup finals in South Africa.
Men’s Health magazine estimates a die-hard World Cup fan could gain 2st and 7lb (15.7kg) if they watch every game between 11 June and 11 July.
It bases this gain on the assumption that a British man watching a game with friends will drink, on average, four cans of lager and eat three slices of a pizza, half a bag of nacho chips and half a pot of dip – adding up to 1,913.5kcal. That’s two-thirds of the recommended daily calorie intake for men, and almost the entire daily intake for women.
In contrast, the energy expended while watching – even accounting for gesticulating, shouting and leaping to one’s feet every so often – is just 215.5kcals.
Source BBC Article
The moral of this is Playing football may be good for the health. Watching it, on the other hand, can pile on the pounds.