The midfielder takes home a note each day from training instructing him what he can and cannot eat.
In southwest Italy he is under the tutelage of Antonio Conte and it has been a fine jaunt so far, with Napoli sitting second in Serie A.
However, his culinary exploits are being strictly guided because of the 'many temptations of Neapolitan cuisine,' as per local newspaper Il Mattino via calcionapoli24.
Antonio Conte is an advocate of the Mediterranean 'Bresaola diet' with plenty of vegetables and protein-rich white meats
That palette, as food lovers can attest, includes ice cream, pizza, pasta, and cheese.
It is a regular protocol for players from abroad to have their diet monitored and Conte wants 'everybody in top form' to achieve their goals.
McTominay in particular is understood to have been warned about the allure of dairy products.
Of course, it is no surprise to see a top European club crack down on what their stars eat.
Conte is known to be a stickler for high standards and when he had Romelu Lukaku at Inter Milan, where they won the Scudetto in 2020-21, he had the strikerlose half a stone within weeks of joining.
Lukaku was accused of being overweight towards the end of his time at Manchester United and reportedly weighed 104 kg upon joining Inter.
Conte had the Belgian adopt his 'Bresaola diet', meaning fried food, mozzarella and alcohol were firmly off the menu, while a Mediterranean menu of vegetables and protein-rich white meats such as turkey and chicken were on the table.
That menu helped Lukaku become an immense success at Inter, where he scored 78 goals in 132 games, won Serie, the Coppa italia, and the Supercoppa Italia, and reached the Champions League final.
At Napoli Conte employs Tiberio Ancora and a platoon of personalised staff to attend to his players' nutrition.
It is reported that McTominay has bonuses tied into his contract if he helps them deliver a league title, so he will be hoping his new diet pays off.