Oh no! Pippa Middleton’s wedding is coming up soon — but she might be going to extremes with her new diet.

The 33-year-old is set to walk down the aisle on May 20 to marry her fiancé James Matthews and she’s using the last couple of weeks to get even more shredded for her big day — but her pre-wedding exercise and diet routine could be bad for her long term health.

pippa middleton james matthews getty images

(Photo Credit: Getty Images)

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Pippa has paired Pilates classes with the SirtFoods Diet, E! News reported, which an eating regimen that restricts the number of calories and the types of food dieters can eat while they complete the two phases of the plan.

Phase one is broken down into two parts. For the first three days, dieters are only allowed to consume 1,000 calories a day worth of SirtFoods — which include red wine, cooca, coffee, kale, arugula, strawberries, and walnuts — in the form of two green juices and one full meal, according to the SirtFood Diet website.

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From the fourth to seventh day, they are instructed to being to increase their calorie intake to 1500 per day and they are can enjoy two meals and two green juices daily. For phase two, dieters will eat three SirtFood-filled meals a day, plus one green juice for 14 days.

But even though the foods are healthy and full of nutrients, registered dietician Birgitte Zeitlin warned against the dangers of crash dieting and said it is both unhealthy and unsafe to eat less than 1,200 calories a day.

“In addition to not giving yourself the proper energy and nutrients you need each day you’re on this fad diet, eventually you’re going to go off of it,” she explained to The Cut. “You’re going to gain all of the weight you lost back, and more often than not, you’re going to gain even more weight back.”

Scroll through the gallery below to see all of Pippa’s best style moments!