Has Kate Middleton put Prince William on a diet?

Does Kate's cooking have something to do with William's svelte appearance? Photos / Getty

Prince William has recently joked that the reason he is "so skinny" is because of his wife's cooking.

But after a trip to Cornwall this week, it looks like the jovial comment may hold an element of truth with the Duke of Cambridge displaying a dramatically slimmer waistline.

William, 34, and wife Kate, took a two-day tour of Cornwall and the Isles of Scilly meeting with young people at a youth centre.

Chatting to locals, William looked trim in a pair of tailored trousers and slim-cut grey blazer.

And compared to photos from a couple of years ago, he appears far less bulky.

William in 2011 and cutting a trimmer figure at an event this week. Photos / Getty

So, beyond his wife's cooking, what's behind the Prince's new silhouette?

According to Rachel Holmes, founder of Kickstart Fat Loss Club, the royal has been swapping sugary foods for healthy carbs and vegetables.

Holmes told MailOnline: "William looks fantastic. Looking at the pictures, he is definitely leaner than he was.

"Judging by the weight he has lost from around his face and mid section, I would guess he has been eating a higher protein diet and cutting out pro-inflammatory foods."

She added: "When you cut out sugar, wheat and gluten and eater higher protein, healthy carbs such as green vegetables and healthy fats like avocado, you lean out and lose that bloated, puffy appearance."