Joaquin Phoenix gets candid about fasting and admits gym session left him feeling worse

Joaquin Phoenix was left in shock by a podcast host's admission about his day long fasts.

The Joker star, who has been vegan since he was three and a half years old, has been known to take part in 'extreme diets' to fit into roles he's playing.

In 2020, the 51-year-old made headlines when he revealed he lost over 50 pounds preparing for his role as Arthur Fleck in the hit films, said he ate a diet of predominantly steamed vegetables and lettuce.

"I’m now 49, I probably shouldn’t do this again. This is probably it for me," he said during a press tour for the movie at the time.

Now, on an appearance the This Past Weekend w/ Theo Von podcast, the star has shared a 'warning' about going to the gym while fasting.

During the conversation, host Theo Von told Phoenix he'd been 'fasting a lot recently' - only drinking water.

The actor once lost 52 pounds for his role in the Joker

"And a little bit of salt, but you even look foward to the salt," the host laughed, before telling the Hollywood legend he even went to the gym during his fasts, which typically last a day to 36 hours. However, the host confirmed that the longest he had fasted for was 73 hours - but most recently, has been fasting for 24 hours once a week.

"Yeah that's great, it's good for you," the actor responded. "But are you sure you should work out while your doing it?" he asked the host, who said he 'wasn't sure'.

"Maybe look into that," Phoenix added. "I don't know, but I remember doing that and I didn't feel good. Maybe it was that."

Is to safe to workout while fasting?

Athletic trainer Jennifer Dix tells Cleveland Clinic that there are 'safe ways to work out while fasting'.

“When you’re physically active while fasting, you have a much higher risk of dehydration and heat illness,” she said. “It’s something to be very cautious about.”

Dix added that the 'safest time' to workout was with the most hydration in your body. Therefore, it's best to schedule workouts before or after a fast.

However, there is little research on the topic, so she recommends tips such as choosing the right time to work out, eating healthy before the fast begins, modifying expectations around your workout and listening to your body.

For those drinking water during a fast, hydration is key before and after.

During a fast where drinking water is not possible, like a religious fast, for example, Dix warns: “There are risks to exercising when you can’t hydrate and don’t have any fuel in your system."

“You’ve got to be cautious and monitor yourself for dehydration issues," she added, which include dizziness, headaches and inability to focus.

The star featured on the This Past Weekend w/ Theo Von podcast (This Past Weekend w/ Theo Von/YouTube)

What impact does a 36 hour fast have on your body?

"Prolonged fasting can have a significant impact on our bodies. After 36 hours, the body may have used much of its available glucose, meaning it will then rely on stored fat for energy," Dr Donald Grant, GP and Senior Clinical Advisor at The Independent Pharmacy, says.

As 'blood sugar can drop' during this time, symptoms including headaches, weakness, tiredness and also irritability or difficulty concentrating can come into play.

“Extended fasting places stress on the body, so anyone with a long-term health condition, those taking regular medication, or women who are pregnant or breastfeeding should always seek medical advice before attempting this type of fast," he warns.