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Gunnar Peterson (Jennifer Lopez, Angelina Jolie, and Sofía Vergara) -

“Your body needs an external load—women especially for bone density, lean tissue, and maintenance,” says Gunnar Peterson. “You need that so your body composition is working in your favor.”

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Bone density in women -

Women happen to have smaller and thinner bones than men on average. When women reach menopause, there is a sharp decrease in estrogen (a hormone that protects bones).

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Harley Pasternak (Lady Gaga, Rihanna, Katy Perry, and Megan Fox) -

Harley Pasternak says that people should watch out for the misconception that “the less I eat, the more I’ll lose.”

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Why to avoid skipping meals -

The consensus is that skipping meals causes your metabolism to slow down and makes your body enter survival mode, meaning you crave all sorts of unhealthy food. Fasting is also dangerous for anyone susceptible to eating disorders.

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Anna Kaiser (Sarah Jessica Parker and Shakira) -

"I love giving myself and my clients gold stars every day that they’ve completed a workout," Anna Kaiser told Motto. "I do that with my client Shakira, and when she was potty-training her son, she would give him a gold star every time he went to the potty, and she got a gold star every time she did a workout. It was a nice way for her to bond with her child."

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Motivation -

To maintain or meet any fitness level, a little motivation goes a very long way. Motivation is a critical factor in supporting sustained exercise. In a sense, this is the one factor that we cannot do without on our fitness journey.

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Justin Gelband (Miranda Kerr, Irina Shayk, and Candice Swanepoel) -

"Food is absolutely number one. When I sit down with anyone to discuss their workout regimen, the first thing I say to them is, 'The one thing I really want you to concentrate on now is limiting the number of things you are putting into your body that you do not need," says Justin Gelband.

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Diet -

The scientific consensus is that diet is as important (if not more important) for almost any fitness or health goal that someone can imagine.

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Ashley Borden (Christina Aguilera and Ryan Gosling) -

"My favorite fat-busting workout is HIIT training (High-Intensity Interval Training). It’s efficient, burns fat, and gains muscle, and you can do [it] anywhere without equipment needed–just your body weight."

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Why HIIT? -

This form of training increases the level of activity that your metabolism operates on, which causes you to burn calories for up to an hour after the training session is over.

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Astrid Swan (Julianne Hough and Kimberly Stewart) -

"I used to think I needed to work out seven days a week, and in the beginning, I was afraid to lift heavy weights and thought it was all about cardio. Now, I work out four to five times a week, lift heavy, and use my time doing more HIIT workouts or ending with a cardio burnout."

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HIIT training -

Indeed, it's been found that HIIT sessions are tremendously effective at burning calories in a short amount of time. You're likely to burn a lot more calories in a 30-minute HIIT session than you are doing 30 minutes of weight training, running, or biking.

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David Kirsch (Heidi Klum, Jennifer Lopez, and Anne Hathaway) -

"The point of workouts are no longer to do double 60-minute sessions or go to classes five times a week," says David Kirsch. "You don't want to burn out and beat your body up." What is crucial is that you do a hybrid of moves that incorporate strengthening and cardio to max out the toning and fat-burning results.

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Looking at burnout -

Burnout can be the result of overtraining or not resting enough and can have significant mental and physical health impacts. It can also occur from not switching up your workout routine enough.

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Erin Oprea (Carrie Underwood, Maren Morris, and Ryan Hurd) -

Erin Oprea says it’s important to “find something that shoots your heart rate up but also brings you joy."

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Enjoyment -

For most people, it's around a thousand times easier to stay motivated when they're doing something they enjoy. This way, when you're out of breath, you don't notice it as much.

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Tracy Anderson (Gwyneth Paltrow, Kim Kardashian, Nicole Richie, and Victoria Beckham) -

"Do 30 minutes of cardio training (dancing, jogging, aerobics) and 30 minutes of muscular structure (weights and stretches). Do it six days a week for the rest of your life," says, Tracy Anderson, adding, "Every day that you don't work out you are gaining weight or staying the same."

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Consistancy -

Inside and outside of the gym, consistency is probably the most important component when working to accomplish goals. Without it, we find it harder to adapt, we're unorganized, and it's harder to form a habit.

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Michelle Lovitt (Courteney Cox, Lauren Graham, and Amber Valletta) -

“Carbs and protein post-workout help to replenish glycogen stores, repair muscle tissue, and reduce cortisol. Cortisol is a stress hormone responsible for many things including the storing of body fat around the middle area. Exercise is perceived stress to the body, so the reduction of cortisol post-workout helps you receive results much faster.”

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Repair and recovery -

After you exercise, your body tries to rebuild its glycogen stores as well as repair and regrow those muscle proteins. Eating the right amount of carbs and protein will help to speed up this process.

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Jeanette Jenkins (Kelly Rowland, Pink, and Alicia Keys) -

"Make the choice to see the positive in everything that comes your way. Every speed bump. Realize that for every valley, there will be a mountaintop. Staying in a positive mindset is going to help you stay de-stressed so that you are enjoying life, which is important to your healthy living. Stress increases your risk of every illness and makes it more difficult for your body to burn fat."

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Keeping a positive mindset -

When we are grateful for what we have and stay positive, everything becomes a lot easier, including our workouts. Keeping a gratitude journal, spending time with positive people, and practicing positive self-talk are all great ways of getting into the habit of seeing the glass half full.

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Nicole Winhoffer (Madonna, Mya, and Rachel Weisz) -

"Being dehydrated weakens my performance and inhibits me from my personal best. Water helps me digest my food and break down the foods so my body can absorb the minerals and nutrients that it deserves."

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Hydration -

The importance of hydrating properly isn't to be understated. Hydrating regulates body temperature, keep joints lubricated, prevents infections, helps the delivery of nutrients to cells, and keep organs functioning properly.

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Mandy Ingber ( Jennifer Aniston, Kate Beckinsale, and Jennifer Lawrence) -

"When I look around there are so many different types of bodies, shapes, and sizes, even amongst celebrities. That really wasn’t the case when I was a teenager. The other thing is that each of us has a body that is our one and only, and for me, I really want my body to feel good."

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Body types -

Did you know that people inherit a certain type of body at birth, with a certain type of skeletal frame and body composition? The three most common body types are ectomorph, mesomorph, and endomorph.

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Sadie Kurzban (Kevin Durant and Tiësto) -

"Get sleep even if it means skipping a workout. I believe that working out is a crucial part of being healthy and happy. It makes us feel better, it keeps us positive and of course in shape. I do not believe in sacrificing sleep for a workout."

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Sleep -

Sleep gives your body time to recover, repair, and build up the muscles worked during exercise.

Sources: (Authority Magazine) (Self Magazine) (BetterHelp)

See also: Shameless celebs who love fast food

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