Hollywood actors often face immense pressure to conform to unrealistic body standards, especially during filming.

The need to drastically alter their physiques often leads to unhealthy diet and exercise habits.

2.Charles Meltongainedaround 40 pounds for his role in the movieMay December (2023).

Two men in priest attire stand before an audience. One uses a crutch. They appear serious and focused. Names unknown

3.Kumail Nanjianigainedabout 25 pounds of muscle for the Marvel movieEternals (2021).

5.Matthew McConaugheylost47lbs for his role as an emaciated AIDS patient inDallas Buyers Club(2013).

McConaugheysaidthe whole process was tough going, Im not going to lie.

A shirtless young man and a woman in a sleeveless dress have a serious conversation while sitting on a bed. Names of persons not known

The dieting was pretty hardcore.

I was losing 7lbs every week.

6.Jared Leto alsolost 40 poundsfor the filmDallas Buyers Club(2013).

A shirtless man stands outdoors with a striped tent in the background. I don't know who he is

He’s said the weight loss affected him.

It changes the way you walk, the way you sit, the way you think.

7.Jared Leto alsolost 28 poundsto play a heroin addict in Requiem for a Dream (2000).

Kumail Nanjiani is in two images: on the left, performing stand-up comedy; on the right, in a detailed, futuristic costume for a movie role

At one point he was even chewing on shoe leather to have a go at curb his hunger.

“I couldn’t walk long distances; I had a wheelchair because it was so painful.

My body was in shock from the amount of weight I gained.”

Kumail Nanjiani works out in a gym, using resistance bands for arm exercises. He wears a sleeveless top and athletic pants

To gain the weight, he shared the one specific food that he ate often.

Ive just eaten a lot of pies, so far, hetoldVariety.

He also went to a professional to help him gain the weight.

Joaquin Phoenix, in a scene from the movie "Joker," looking upward with a serious expression, wearing a button-up shirt and a cardigan sweater

11.Bradley Cooperhad togain a noticeable amount of weight for his role inAmerican Sniper(2014).

He ended up gaining over 40lbs while training.

Bradleysaid, It was a real shock to my body.

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If its pizza and cake, thats one thing.

Putting 6,000 calories a day in your body gets old quick.

He did this by having a liquid diet andrunning on the treadmillfor three hours a day.

Matthew McConaughey in a gray suit and light shirt at a public event

I was so into what I was doing that I wasnt really concerned with that.

I just kept looking at myself in the mirror feeling like I have to be smaller.

I had to match.

Matthew McConaughey sits on a hospital bed in a plain t-shirt and pants, with visible facial bruises and a mustache

Just tried a new diet/training program called “Lost At Sea”.

His diet consisted mostly of chicken breast.

He gained over 30lbs for it.

Jared Leto, left image, at a G-Star event with denim jacket and striped sweater; right image shows Leto in a movie role with curly hair and floral blouse

I certainly have joints that click that probably shouldn’t click, you know what I mean?

And carrying my children is a little bit harder than it used to be."

George ended uphospitalizedwith pancreatitis four days before filming began.

Jared Leto is seen in two separate scenes, one wearing a beanie while looking concerned and another shirtless, leaning forward over a sink

For 24/7 crisis support, text NEDA to 741741.

A man, wearing glasses and a jacket with a scarf, stands outdoors

A man with a gaunt and emaciated appearance stands shirtless in a doorway, looking into a room where another person lies under a white sheet

Christian Bale attending an event in a black suit and tie, with a serious expression

Christian Bale, in character, wearing glasses, a blue shirt, and a gold watch, rests his chin on his hands while staring thoughtfully

A photo of Bradley presenting an award in 2013

A photo of Bradley in American Sniper in 2014, when he has gained a substantial amount of weight compared to the previous photo

50 Cent in a black suit and shirt poses in front of a branded backdrop at an event

A shirtless man with an oxygen tube lies in a hospital bed, looking distressed

Chris Hemsworth, in a rugged shirt, gazes up on a ship's deck in a scene from a movie

A photo of Matt Damon in the movie, when he looks very thin with a sunken face

A photo of Matt Damon before filming the movie, when he looks healthy

Tom Hardy as Bane in "The Dark Knight Rises," shirtless, wearing a mask

Side by side photos of Tom Hardy in 2010 and 2011, with him looking significantly bigger in the later photo

A man with a gray beard and short hair, wearing a plaid shirt and gray t-shirt, stands in a hallway

George Clooney speaking at a podium with a "Variety Power of Women" sign