JAY PHAROAH TOOK to Twitter to share his most recent fitness update, and it's pretty extreme if you ask us.

The former Saturday Night Live star said that he lost 20 pounds in 21 days. When a follower asked how he did it, Pharoah said all it took was a "controlled diet" and a lot of high speed running. He's been grinding out 6 to 8 miles a day since the start of the new year, clocking in at 12 miles per hour. That's nearly a 5-minute mile.

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Before you try to lose a pound a day, know that losing weight this fast is not recommended by most health professionals. While it's possible to loose several pounds in a short amount of time, it's not the healthiest way to go about shedding weight.

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Plus, you likely won't be losing the kind of weight you're looking to loose.

Extreme diet and exercise programs often lead to dehydration, so the lost weight is likely mostly water weight, David Creel, Ph.D., R.D., a psychologist and registered dietitian in the Bariatric and Metabolic Institute at Cleveland Clinic, told Men's Health.

“You can see people who maybe lose 20 pounds in a week intentionally—but it’s very risky,” Creel said.

These intense diets may also cause muscle to deteriorate, ultimately causing our metabolism to suffer. When our metabolism slows down, we end up burning less calories at rest, which makes sense, considering muscles require more energy to maintain than fat.

“If someone goes on a pretty restrictive diet, they might lose 20 percent to 25 percent of their weight as muscle,” said Creel. He recommends a weight loss goal of 1 to 2 pounds per week to avoid these adverse health effects.

Plus, extreme diet and exercise programs are just flat-out unsustainable, causing you to gain even more weight when you decide you're done.

While Pharoah's transformation is motivating, don't feel like you need to get cut as quick as he did. A healthy calorie deficit, exercise, sleep, and hydration will all help you get to where you want to be. It's just a matter of consistency!

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Cori Ritchey

Cori Ritchey, NASM-CPT is an Associate Health & Fitness Editor at Men's Health and a certified personal trainer and group fitness instructor. You can find more of her work in HealthCentral, Livestrong, Self, and others.