Revealed: The diet that helped Prince Harry lose weight for his wedding

Prince Harry appears to be cutting a sharper, slimmer figure in the run-up to his wedding and speculation is rife that Meghan might have nudged him towards the London gym much loved by her future sister-in-law, Pippa.

He has been spotted coming in and out of KX (pronounced 'kicks'), the exclusive Chelsea gym where Pippa famously trimmed and toned her slender frame in preparation for her wedding last year.

It could be the top-of-the-range gym equipment, expert personal trainers and disco-themed spinning studio that are transforming Harry's beefy, beery body, but it's very likely Meghan has put him on the special green juice diet that KX recommend, according to the Daily Mail.

Their aim was to devise a "fast-track" diet that would guarantee maximum athletic performance and speedy weight loss. The result was the Sirtfood Diet book, which hit the bestseller lists when released in 2016.

The KX ethos is so Sirtfood-entrenched that much of the on-site restaurant is "sirtified" with on-message Sirtfood salads ($39), green juice ($23) and energy bites ($6.80).

Despite Pippa's obvious success with the regime, there's nothing girlie about the Sirtfood Diet. Chocolate, coffee and red wine are allowed, and, unlike the intermittent fasting regimes so popular with many men, there's no requirement to go hungry.

However, the diet's creators have come under fire from dietitians for devising a regime that strays from government advice.

The initial seven-day kickstart suggests green juice as a meal replacement, which goes against the Food Standards Agency's balanced EatWell Guide plate or the food pyramid that NHS dietitians typically fall back on.

But Goggins and Matten indignantly point to their eminent qualifications: both have a masters degree in nutritional medicine. Goggins is also a qualified pharmacist.

They hit upon the idea of Sirtfoods after following up on an investigation into the life-enhancing properties of a plant chemical called resveratrol, found in grape skin and red wine, which scientists speculated could hold a key to longevity.

The duo discovered that other foods — such as walnuts, capers, red onions and dark chocolate — contain specific natural plant chemicals that appear to be able to activate genes in our bodies.

These genes are known as sirtuins — so Goggins and Matten named the foods with the most abundant natural chemical profile "Sirtfoods".

Each Sirtfood provides a different combination of phytonutrients and supposed health benefits, but the pair found that combining Sirtfoods appears to enhance their active powers.

"One food might contain a chemical which helps prevent fat formation and another helps increase fat disposal," explains Goggins, "you could eat a whole field of kale, but get nowhere near the benefit that a Sirtfood-loaded meal would bring."

The authors were so excited about the proposed effects on blood sugar levels and fat metabolism that they agreed to a trial into the health impact of a seven-day intense boost of Sirtfoods.

Goggins says: "The trial was designed to measure how the diet stimulated rejuvenation and cellular repair.

"We added a degree of calorie restriction, because studies show it is good for longevity, so we knew people would lose weight, but we had no idea the average weight loss would be half a stone."

That's one big reason the Sirtfood diet appeals to men.

"The dieting culture has got stuck in a rut, with experts advocating eating less and less.

"Suddenly, everything that you enjoy seems to be bad for you. People are getting fed up with conflicting messages and confusion. It's such a shame,' says Goggins.

"When giving up food is routinely offered as the 'solution', surely something has gone very wrong.

Our seven-day plan is an optional kickstart. The most important message is to be adding Sirtfoods to your existing diet — the benefits come from the foods you eat, not from foods you have to avoid."

Daily Mail