He has trained Kim Kardashian, Megan Fox, Hilary Duff and Katy Perry, who, star trainer Harley Pasternak says, are "all fun to work with, all very motivated as they make a living based on how they look.
"All my clients want to get red-carpet-ready and looking great very quickly – this week."
Kim Kardashian, 32, has said "I live for Harley's smoothies!" They taste incredible!"
And now we can taste them and get red-carpet-ready in record time, thanks to the famous fitness guru's new diet book, where he focuses on super healthy smoothie recipes and actually tells us to exercise – not more, but less.
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Harley exclusively explains to HELLO! Online that Kim tried and loved the smoothie diet from his new book The Body Reset Diet. "She can still incorporate the smoothies into her daily routine and get the nutrients in her body even while she's pregnant".
As the diet promotes short daily exercise regimes, Kim can do those, too. Harley says that his new book is a safe, healthy, rapid weight loss programme that incorporates blending, healthy convenient snacks and simple recipes for traditional meals, and it doesn't require you to go to the gym. In fact, Harley believes that we exercise too much.
"We are underactive and over-exercising," he says. "We've stopped walking, we don't take the stairs, we're on the internet all day, and then we try to compensate with intensive class. Then we feel like we can eat dessert and suffer injuries from working out too hard.
Super high intensive class does not make up for 23 hours of doing nothing. There's no amount of exercise in the world that can make up for a bad diet."
Instead of trying to compensate for being inactive, the celebrity trainer's trick is to "keep moving from the moment you wake up until you go to bed. Keep moving so you don't have to go to the gym." He recommends walking at least 10,000 steps a day.
His new book details five-minute circuits that become "part of your daily life", and includes an eating plan with recipes that make serious use of your blender. The aim, of course, is to reset your body, appetite and metabolism.
How exactly does the diet work?
"There are three phases," he says. "They're each five days long. Phase 1: You're going to blend three times a day, just for five days. You have a white smoothie for breakfast, a red one for lunch and a green one for dinner. It's balanced and healthy and you're not eliminating any food groups. In the first five days people can lose between one and five kilos. In the second phase you replace one smoothie with a solid meal that includes soups, salads, sandwiches, stir-fries and sushi and in the third, you replace another smoothie with a solid meal."
Harley chooses to focus on blended recipes because they are super healthy and provide us with all the nutrients we need, at the same time as losing the pounds. Don't get confused with the difference between blending and juicing, he warns. "Blending is far better than juicing. All parts of the vegetable work together. By juicing, you only take the water, sugar and some of the nutrients, and you need the rest."
Harley's final tip? "Make sure you leave the skin on your fruits – that's where the nutrients and fibre are."
Now you can look like the stars in no time by trying out Harley's healthy, balanced smoothies, exclusively shared with HELLO! Online.
Interview by Miriam Foley
The Body Reset Diet is published by Simon & Schuster UK, £12.99