Guardiola reiterated the policy after City's 3-0 win over West Ham United on Saturday.
He said all players had been weighed before the break and would be weighed again during training on Christmas Day.
"Every player was weighed on Friday. They come back on the 25th and I will be there to control how many kilograms they have gained," the Spanish coach told the Premier League website on Monday.
He stressed the importance of discipline during the short break, although he understood the players would be celebrating Christmas with their families.
"They can eat, but I want to control them," said Guardiola.
He also emphasized the consequences for players who experience significant weight gain ahead of the next match.
"Imagine a player who is in perfect condition now, but he comes in three kilograms heavier. He will stay in Manchester. He will not go to Nottingham Forest," Guardiola said.
