Kevin de Bruyne and Scott McTominay have been forced to follow a strict rule at Napoli after leaving the Premier League.
The Belgian and Scottish midfielders will return to Manchester on Thursday night, when they take on Manchester City in the Champions League.
For De Bruyne, it is a return to the Etihad Stadium where he spent 10 years, winning six league titles and a Champions League crown. Former Manchester United stars McTominay and Rasmus Hojlund will also be hoping to get one over their old rivals.
But they have all been kept under close observation, as Napoli aim to retain their Serie A title.
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According to Calcionapoli24, McTominay's diet was closely monitored due to the 'temptations' of Italian food when he joined last summer. Given both de Bruyne and Hojlund made the switch from England to Italy this summer, it is assumed they will have been placed under the same observation.
The report said: "Nutrition for Napoli players is fundamental and Antonio Conte knows it well.
"He wants everyone in top form and that's why he relies on Tiberio Ancora and his staff.
"The temptation of Neapolitan cuisine can be strong so here comes the warning for a series of foods to avoid, such as dairy products for example."
How will Kevin de Bruyne fare against Manchester City?
For de Bruyne, Thursday's night trip to Manchester will be an emotional affair as he returns just months after leaving Pep Guardiola's team.
But his focus will be on trying to ensure his Napoli side emerge with three points from the opening week of fixtures.
He has settled impressively into life in Italy, scoring two goals in three games, including a stunning free-kick in the season-opening victory over Sassuolo.
The 34-year-old was also in good form in Belgium's recent World Cup qualifiers, bagging a brace against Kazakhstan.
Before his move to Naples, de Bruyne bid farewell to Manchester City with an emotional message to supporters.
He said: "Nothing about this is easy to write, but as football players, we all know this day eventually comes. That day is here- and you deserve to hear it from me first.
"Football led me to all of you-and to this city. Chasing my dream, not knowing this period would change my life.
"This city. This club. These people... gave me EVERYTHING. I had no choice but to give EVERYTHING back! And guess what we won EVERYTHING. Whether we like it or not, it's time to say goodbye."
Topics: Champions League, Football, Kevin De Bruyne, Man City, Manchester City, Napoli, Premier League, Scott Mctominay, Serie A
James Taylor