Jennifer Aniston and Reese Witherspoon are both fans of intermittent fasting.
This means they don't eat any solid food for 16 hours every day.
"The Morning Show" costars do drink coffee and juice in the mornings, they told Radio Times.
While there are proven health benefits of intermittent fasting, such as lowering your blood pressure and increasing longevity, nutritionists and dietitians have pointed out that it may not work for everyone.
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Jennifer Aniston and Reese Witherspoon are both fans of intermittent fasting, where you increase the daily overnight window in which you don't eat food.
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The actors and costars of "The Morning Show," which launches on Apple TV+ on November 1, told Radio Times that they shun solid food for 16 hours every day, leaving them a window of 8 hours for eating.
"I do intermittent fasting, so there's no food in the morning," Aniston, 50, told the magazine.
"I noticed a big difference in going without solid food for 16 hours."
While some advocates of intermittent fasting say all you should consume during your fasting hours is water and tea or coffee without milk or sweetener, both Aniston and Witherspoon prefer to stick to a liquid diet in the mornings, drinking juice and coffee.
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Aniston said that she's a night owl and usually wakes up at around 8.30 a.m. or 9 a.m.
"Today, I woke up and had a celery juice," Aniston said. "Then I started to brew some coffee, but I don't drink coffee that early."
The actor then fed her dogs, meditated, and worked out before drinking her coffee.
Witherspoon added: "I just have a green juice and a coffee in the morning."
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Her morning routine, however, starts somewhat earlier than Aniston's, as she says her 7-year-old son wakes her up at 5.30 a.m. to 6 a.m. every day.
Witherspoon, 43, admits that she is in fact a morning person, but says she doesn't love exercising early.
"I find it really hard to work out before 7.30 a.m. But that's the time I start one: 7.30 a.m," she said. "I probably do that six days a week."
Although Aniston said she works out one fewer day a week than her costar, Witherspoon said she often asks Aniston for "wellbeing" advice because she "knows so much" about health and fitness.
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"Well, we want to thrive, right?" Aniston said. "We're just beginning."
Intermittent fasting has proven health benefits
Intermittent fasting has become increasingly popular in recent years and studies have found a slew of health benefits, from lowering your blood pressure to increasing longevity.
While some people decide to take on the practice as a means to lose weight, most experts agree that the main reason it may lead to weight loss is because having a smaller window of eating means you consume fewer calories.
"This type of fasting often results in the consumption of fewer calories overall, which contributes to weight loss," University of Michigan Medicine dietitian Sue Ryskamp said earlier this year.
Registered nutritionist Rhiannon Lambert agrees, writing: "The overall picture is that this is most likely due to overall calorie reduction, rather than the results of the fasting diet itself."
However, research from January 2019 by Monash University in Melbourne, Australia, published in the British Medical Journal, found that skipping breakfast could help people lose weight.
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Hollywood personal trainer and physical therapist David Higgins, who has worked with the likes of Margot Robbie, previously told Insider he believes breakfast is overrated.
But intermittent fasting doesn't have to mean skipping breakfast: If you prefer to eat in the morning, you can have your final meal earlier in the day to begin your fast then.
It needn't be a 16-hour fast, either - some people start by splitting their day 12.12 a.m. and then gradually increasing the length of the fasting window.
Intermittent fasting isn't for everyone
Many nutritionists and dietitians have pointed out that intermittent fasting may not work for everyone, as some people simply function better when they eat throughout the day.
"Fasting can be a slippery slope to unhealthy habits and a screwy relationship with food," registered dietitian Jessica Cording wrote for Shape.
She also points out that for most people, it simply isn't a sustainable way to live and eat.
Lambert adds that fasting can lead to fatigue, low mood, low energy levels, and ultimately overeating.
"If you enjoy breakfast, then there is no need to fast until lunchtime because someone else lost weight from it," she said.
"There is no 'magic' behind intermittent fasting, and it is not superior as a weight loss tool, but it is an interesting area of research that may well expand."