3 Essential Weight Loss Tips From Rihanna, Kim Kardashian, and Amy Schumer's Trainer

Harley Pasternak has shaped some of Hollywood's strongest, healthiest bodies. From getting the already-fit Halle Berry in even better shape for Catwoman to training Amy Schumer for her role in Trainwreck to keeping Ariana Grande, Jessica Simpson, and Kim Kardashian camera-ready, he knows a thing or two about helping women shape up.

So of course, when we sat down with him, we were dying to know all of his best fitness and weight-loss advice (and how he helps his star clients lose weight!). His top three tips for weight loss are simple, quantifiable, and easy to implement — starting now! It comes down to movement, sleep, and nutrition. Numbers to remember: 10K, 7, and 5.

1. Move at Least 10K Steps a Day

"That is a minimum," said Harley. "For a lot of people, this is a real, simple thing to start with. I don't [tell clients] you need to start eating tofu, become gluten intolerant, whatever — just start moving. Be a little more active."

He mentioned that one good choice leads to another, and starting with simple movement goals can build into something even bigger. It works, too. We interviewed a woman who lost 10 dress sizes by starting with a goal of 10,000 steps per day on her Fitbit.

"All of the sudden, you start being conscious of other behaviors. You grab that scone in the morning and you realize, wait, 'I just got off the subway two stops earlier so I could walk a little bit; I'm gonna undo that and then some by making this food choice. Let me be a little more conscious about it. I'm gonna have half the scone, or instead of the scone I'm gonna have the apple.' It all starts with steps."

2. Get at Least 7 Hours of Sleep

"Sleep has such a profound impact on weight lost, amongst the most!" he told us.

There's science to back it up, too. Less sleep, more pounds. "We know hormonally when you don't get enough sleep [there's an influx of] ghrelin, leptin, and cortisol: one will make us eat more, one will stop us from burning body fat as efficiently, one will make us more vulnerable to store body fat."

As if that weren't bad enough, fatigue will also create more roadblocks on your weight-loss journey. Harley told us, "You'll be less likely to be active the next day if you're tired, and you'll mentally not be on par to make smart food decisions." Ready to lose weight? Start getting some zzz's.

3. Eat Protein and Fiber 5 Times a Day

Harley recommends you get a large intake of protein and fiber, spread out over three meals and two snacks, every day, as well as healthy fats! "Protein, fiber, and healthy fats: that's the Holy Trinity of satiety." He noted that these nutrients are the things that make us feel full and spur our metabolism.

To make sure you're meeting your daily needs, Harley recommends food logging. "I have a lot of clients take photos of what they eat, and at the end of the day they look at this visual log — you're eating it, taking a picture of it, logging it, writing it down, looking at what you did later." This is also to promote mindfulness and accountability.

We also got a little insight as to what it's like to be one of Harley's star clients. "All my clients have to email me at night before they go to bed with a screenshot of their Fitbit app, [which shows] what they ate, how many steps they got, and how their sleep was the night before." Seems simple enough, right?