Queen Elizabeth's Stay-Trim Secret? A Diet 'Heavy in Butter and Cream' But 'No Starch for Dinner'

Don’t mess with the Queen’s food.

Though a lot has changed during the 63 years and 7 months that Queen Elizabeth has ruled, one thing has stayed consistent: her taste buds.

“The royal table hasn’t changed much at all in 63 years,” former palace chef Darren McGrady tells PEOPLE. “One thing about Her Majesty is continuity and the same menus, just allowing new ones to creep in gradually.”

As Britain’s longest-reigning monarch, the Queen and her family were “pioneers of modern day food trends and ‘farm to table'” dining, notes McGrady.

“All through her reign she has insisted on food in season. She is happy to eat strawberries from her garden five days in a week at Balmoral in the summer,” says McGrady, “but never in January.”

While the Queen is entertaining, she eats meals “heavy in butter and cream” but when eating alone, she sticks to simple meals like grilled chicken with salad to keep her slim figure.

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“She’s very disciplined,” says the chef who also cooked for Princess Diana. “No starch is the rule. No potatoes, rice or pasta for dinner.”

And although she is invested in a healthy diet, “sadly the Queen is not a foodie,” says McGrady. “She eats to live.”

—Ana Calderone with reporting by Simon Perry