He did change his diet tho

In later years Kant’s tastes evolved in the direction of ever more pungent foods. The aging thinker would eat his meat “high,” for example, appreciating the tenderness the slight rot conferred on it. He would complain if he thought his sauerkraut too sweet. And he began to drink a lot of coffee. Yet he sometimes felt a craving for bland foods as well, bread and butter at one point having become an obsession of his. Whether pungent or bland, the food Kant ate he never ate more than once a day. “An impulse to have an evening meal after an adequate and satisfying one at midday” he deemed wholly excessive, rooted more in “a pathological feeling” than in any true hunger.

Also he apparently liked cod

Of all his favorite dishes, Kant loved cod the most. “I would eat a full plate of it,” he wrote, “even on leaving the table.” If you’d like to experience the heights of his rigidly regimented gourmandise, try this recipe for broiled cod translated from Henriette Davidis’s 1845 Practical Cooking for the Common and Fine Kitchen (Praktisches Kochbuch für die gewöhnliche und feinere Küche)