England boss Fabio Capello introduced a strict regime which forces the national squad to go up to eight hours without food after training sessions.
But top stars have smuggled bags of crisps and chocolate bars into their rooms as they fight hunger pangs, according to sources.
The Sun reports of one senior source in the England camp, saying: "Players were complaining of feeling light-headed and nauseous after training. They’d been together four days and couldn't believe how little they'd eaten. Most are used to diets packed with carbohydrates to keep going. Now all they're allowed is a bit of cereal and toast.
"It got so bad that some started smuggling supplies of chocolate and crisps into their rooms behind Capello's back."
The diet plan has even seen one player -believed to be Manchester United defender Rio Ferdinand - reportedly vomit at half-time during the friendly against the Czechs at Wembley.
The source said: "One senior player started suffering stomach cramps and was sick all over the dressing room floor. This isn't about the players being greedy. But suddenly they were going long periods with nothing to eat and their systems couldn't cope."
The source added: "There's been a bit of moaning about the diet behind closed doors, but no one's been brave enough to confront the boss head-on."