Pippa Middleton
Pippa Middleton attends the British Heart Foundation: Roll Out The Red Ball at The Savoy Hotel in London, England, on Feb. 11, 2016. Photo: Getty

Pippa Middleton is set to tie the knot with James Mathews on May 20 and she is leaving no stone unturned to keep fit. She was seen attending a 75 minute long pilates class at exclusive club and private fitness center KX Gym, according to E! News.

Fitness fanatic Pippa climbed the Swiss Alps for charity last April, completing the 33 mile course in five hours 58 minutes. She also participated in the Inferno race in Switzerland a few months before the Alps course. She competed in the Birkebeiner Ski Race in Norway almost a month later.

Her strict fitness regime is supplemented by a healthy diet. The younger Middleton is a huge SirtFood Diet fan. The plan devised by Aidan Goggins and Glen Matten incorporates 20 SirtFoods, including red wine, cocoa, walnuts, arugula and kale strawberries, which when consumed in the right proportions can help the body burn fat and speeds up metabolism.

Pippa Middleton attends the BGC Annual Global Charity Day at Canary Wharf in London, Sept. 12, 2016. Getty Images

Her diet starts off with a seven day phase, three days of 1000 calories followed by three 1500 calorie days and lots of juices throughout the period. The second phase marks the return of three major meals of SirtFoods a day, E! News reported.

Pippa is all set for her wedding day and Kate Middleton, being the supportive elder sister that she is, has been busy with the wedding preparations too. Spotted at Pippa’s London residence, the Duchess of Cambridge kept it casual with a pair of shiny black jeans and cable knit jumper teamed up with a pair of her on-the-go Superga sneakers.

Pippa’s wedding will have royal babies Prince George and Princess Charlotte playing important roles. Kensington Palace announced Monday, April 10, that Prince George will be the page boy while Princess Charlotte will be the bridesmaid at their aunt’s wedding.

The rest of the royal family is expected to be present but Prince Harry might not get to bring his girlfriend Meghan Markle along as Pippa has a strict “no ring no bring” policy, allowing no bachelor to bring their partners as plus one.