In 2009, the "Backstreet Boy" was diagnosed with cardiomyopathy, or weakening of the heart. For ten years prior to his diagnosis, Carter had been battling drug and

alcohol addiction, which lead to his weight gain.

While promoting his solo album in 2011, Carter told FOX411 that he attributes his weight loss to exercise and a healthy diet, two things he continues

doing today. 

“I freak out if I go a little too long without being in the gym," he said. "For a long time it was all about getting the weight

off because I was 240 pounds at my heaviest, and now I’m around 175, so the majority of that weight loss was due to diet and exercise.”

Before we knew Chris Pratt as Star-Lord, he was the baby-faced Andy Dwyer. When he first auditioned for the Marvel film, he weighed nearly 300 pounds. So how

did he drop 60 in just six months?

“Three or four hours a day of just consistent, ass-kicking hard work,” Chris told Men's Fitness. All that work definitely paid off! DAYum, Chris Pratt.

In October, Janet showed off her 70-pound weight loss at the Hollywood Bowl. In an interview with Essence, Janet's personal trainer Paulette Sybliss said she got the pop singer back in

tour-ready shape by focusing on building muscle.

"We did no conventional cardio whatsoever," Sybliss said. "A lot of people find that really hard to believe. It was all weight training

and it was the type of weight training that I did, so we would incorporate exercises back-to-back. I didn't just want her to lose weight; I wanted her to drop body

fat."

Pop princess Christina Aguilera is no stranger to weight struggles and admits she's been on both sides of the spectrum when it comes to her size.

"I've been through my

highs, I've been through my lows," she told Marie Claire. "Being too thin. Being bigger. I've been criticized for being on both sides of the scale."

But thanks to her personal trainer Tee Sorge, the singer was able to drop more than 50 pounds in 2013. PEOPLE reported that the "Voice" judge

has been exploring new foods and different forms of exercise, which has been great for boosting her mind, spirit, and overall health. And we gotta say, our girl Xtina is

looking great!

This "Dreamgirls" star has come a long way since her "American Idol" days. Despite rumors accusing the vocalist of surgery and yo-yo diets, Hudson has maintained her 80-pound

weight loss for nearly seven years. 

Today, Jennifer has swapped her size 16 for a size 6, and she's looking better than ever. She attributes her figure to a strict diet.

"I don't really have time

to do much [working out], so I really just watch what I eat," she said. "I'm very careful and cautious of what I'm eating, so I just try

to pace those meals throughout the day. Like, okay, eat here, don't eat here. When it's early in the morning, I say, okay, I would've been asleep ... so I'm

not going to eat. I'm very conscious of what I put in my body." 

After filming "War Dogs" with co-star Miles Teller in 2015, a role for which Jonah put on some weight for, he reached out to Channing Tatum for some fit-inspo:

"I

called Channing Tatum and said, 'Hey, if I ate less and go to a trainer, will I get in better shape?'" Hill said on "The Tonight Show" in

August 2016. "And he said, 'Yes, you dumb motherf--er, of course you will. It's the simplest thing in the entire world."

After gaining nearly 40 pounds for his role in "War Dogs", Hill reportedly hired a nutritionist and also kept a food journal. And, he's looking better than ever!

Keep it up, Jonah!

Back in 2014, the "American Idol" vocalist appeared on "Today" to talk about her body transformation. She said her motivation was to simply take control of her health. 

"I was

comfortable with how I looked before, but it was about really focusing on become healthier," she said. "And then my body changed, which was awesome. But it wasn't

about being a size zero, or anything like that."

In her 2014 "Today" interview, Sparks revealed that she'd shed more than 50 pounds with just diet and exercise. She's continued her fitness journey and regularly posts sweat-seshes at the

gym on her Instagram. Plus, the singer just recently announced that she and hubby Dana Isaiah have a baby on the way! Congrats, fit mama!

Oprah Winfrey has always been candid about her lifetime battle with food. In January 2017 she spoke with PEOPLE about her recent weight loss. The mogul revealed she

was determined to lose 20 pounds in 2015, but ended up gaining nearly 17 extra pounds after an ankle injury.

In the same cover interview with PEOPLE, Oprah dished on what she eats every day, which has attributed to her more than 42-pound weight loss.

The "Revenge Body" star has been completely transparent with her social media followers, especially when it came to her more than 40-pound weight loss after her split from

NBA star Lamar Odom. 

"If you were to ask me five years ago if I ever saw myself being completely in love with fitness and health, that I would be

an inspiration to many others, that I would be the push that others needed to find their way, I would've laughed in your face," she wrote on Instagram.

"Me? The chubby one? No way!"

"Sometimes it's hard for me to post these transformation posts only because I can't imagine my life being this unhealthy again. Never would I ever consider myself fat, but I

would consider myself unhealthy: mind, body, and soul," the reality star wrote on Instagram. "For me, my transformation journey started from within. I needed to heal myself from

the inside out. Once I started putting myself first, everything started falling into place. My life transformed a few years ago when I made the decision to stop existing and

start living."

In December 2015, Drew revealed that when he was on "The Drew Carey Show" his unhealthy habits got out of hand. 

"When I was doing [The Drew Carey Show], I was

eating a lot of garbage, I was drinking a lot, so I had a lot of mood swings," Carey told SUCCESS magazine. "I had diabetes.”

Now, "The Price Is Right" host has dropped nearly 100 pounds, thanks to a strict diet and exercise plan. He also revealed he's been able to control his

diabetes without medication.

The "That's So Raven" star told PEOPLE that she's never been ashamed of her body. 

“I could look in the mirror and see me at 200 lbs. or

135 lbs. and I’m still the same person,” she said. 

But in 2007, Symoné took some time off from Hollywood to make her health a priority. 

Symoné lost more than 70 pounds, thanks to 30-minute elliptical workouts at least four times a week.

Star Jones' painful weight battle has been in the public eye since she first appeared on "The View" in 1997. By 2003, Jones weighed more than 300 pounds. 

Jones made the ultimate decision to receive gastric bypass surgery for her health. Afterward, Star lost more than 150 pounds. 

In this ad for NutriSystem, Hart revealed her before-and-after weight loss pics. She said that losing weight after having her third child was harder than before. She credits NutriSystem for

her 30-pound weight loss.

In 2016, Hart revealed her swimsuit-ready body on Instagram, dishing that she'd lost 40 pounds thanks to NutriSystem. 

"I want to show [my children] how to be healthy,"

she said.

Funny girl Lena Dunham has been pretty open about her body weight battle. But she's always tried to preach body-positivity on her own journey to get healthier. 

“I have been 30

pounds heavier and I’ve been 30 pounds lighter, and it has never had an effect on my ability to find love or connect with people," she’s said in

the past. 

In July, Lena posted a photo of her weight loss journey on Instagram, this time in a latex bodysuit. A month earlier, she shared a nude pic with

a body-positive caption:

"I spent so many years loving my body but thinking it wasn't lovable by others- its sole purpose was to be fodder for jokes. I performed the

insult so no one else could. I don't regret any of it- that's my art and that was my truth- but now, at age 31, having been through hell and

back with my health and other people's perceptions of my physicality, I feel deeply comfortable with the idea that this pear-shaped pot of honey is equally good for making people

laugh and laying out like a Suicide Girl circa 2004. Love it all."

After undergoing weight loss surgery, Mama June got help from trainer Kenya Crooks to maintain her results. She continued to eat healthy and exercise regularly until she got to her

goal weight. 

In an interview with PEOPLE, Mama June revealed that since her gastric sleeve she's lost 300 pounds. She plans to keep the weight off by eating healthy, exercising,

and focusing on portion control. 

"I can promise you I'm never going back to that size," she said. "I'm happy where I'm at."

It's hard to envision Seth Rogen as a lean green machine, but that's what he did to get in shape for "The Green Hornet". He followed Hollywood trainer Harley Pasternak's

"5 Factor Diet," which included exercising and eating in increments of five times, daily.  

Rogen trimmed down and lost 30 pounds for his role in "The Green Hornet". 

“I’ve been eating better and training—and hating myself for it," he said. "I feel

like a sell out, I feel lame, I feel like a guy I would make fun of.” 

It's not uncommon for actors and actresses to be asked to gain (or lose) weight for a role. Unfortunately, this is not always done in a healthy way. In order

to play the lovable Bridget Jones, Renée Zellweger was forced to gain 30 pounds, twice. 

A year later following her Bridget Jones fame, Renée had slimmed down to play Roxie Hart in "Chicago". 

"I had a panic attack with all the specialists talking about how

bad this is for you long-term, putting on that much weight in short periods of time," Zellweger said.

The "Hot In Cleveland" star has always been open about her weight loss struggles. Valerie told PEOPLE that in 2007 she weighed 172 pounds. Two years later, the

Hollywood star found a way to drop the weight. 

In 2009, Valerie graced the cover of PEOPLE magazine in a bikini - wearing one for the first time in 30 years. She attributed her 50-pound weight loss

to exercising. She revealed that she went from walking 10k steps a day to running five times a week.

After a crazy time on "The Jersey Shore", Nicole “Snooki” Polizzi turned things around. After having a baby, the reality star made health a priority. 

By June 2013, Snooki was showing off her toned tummy on Instagram. She wrote: "Getting more toned & defined !!"

In January 2013, she told PEOPLE she's serious about fitness:

“I go [to a trainer] four times a week, and we do legs, arms and everything,” she said. “And after every one-hour workout, I do an hour of

cardio. I’m still working my ass off, but it’s all worth it. I’m now motivated and I want to change my body. It’s a good feeling to work out because

I feel much better. Plus, my guy Jionni likes it.”

After undergoing gastric bypass surgery in 2002, the "Today" weatherman dropped almost 150 pounds. At his heaviest, Roker was roughly 340 pounds. 

Roker has managed to keep the weight off, despite having a difficult period that caused him to gain back almost 40 pounds. Afterward, Roker went on a cleanse to detox

his body in order to lose the extra weight. 

He's been able to keep the weight off by eating unprocessed foods packed with protein and low in carbs. Additionally,

Roker plans three 30-minute workouts each week and strength trains regularly. 

After watching his "Pawn Stars" co-star Corey "Big Hoss" Harrison shed nearly 200 pounds, Austin "Chumlee" Russell decided it was time for him to do the same. 

“It was time for me

to get healthy,” Russell told PEOPLE. “I started at 320 lbs. and now I’m down to 225. When I first began, I eliminated all processed foods except mustard.

Now, ‘everything in moderation’ is my motto.”

In 2014 the reality star had reportedly lost almost 100 pounds. He attributed his weight loss to diet and exercise. 

“I’m going to the gym six days a week,”

target="_blank">he said. “I’m eating right. Well-balanced diet. I drink a juice smoothie every morning.”

After competing on "Dancing With The Stars" (and reportedly dropping 20 pounds in the ballroom), Ricki Lake took her weight loss a step further. 

In a 2007 interview with Access Hollywood, Lake revealed that at her heaviest, she weighed 260 pounds and was a size 24. At the time of the interview,

Lake was making headlines for dropping down to a size 6 and weighing 120 pounds. 

Paula was able to drop more than 35 pounds with small diet and exercise changes. 

She told SHAPE that she lost weight by simply walking 30 minutes each

day on the treadmill and by incorporating a strict diet. 

"I really changed the landscape of my plate—I filled it with more greens and less starches," she said. "In the

South, there’s a perception that we’re all about fried food, when in reality, we’re about fresh food. My table is always filled with great vegetables, and I really have been

eating more of them—more veggies and more salads—and loving it."

Kirstie Alley has always been open about her weight struggles, but after dropping more than 50 pounds with Jenny Craig, she's been working hard to keep it off.

So, how did she do it? She told PEOPLE that she has maintained her weight loss by avoiding three things: pasta, sweets, and cheese. 

After giving birth (in both 2012 and 2013), Jessica Simpson was determined to lose her baby weight. So she enlisted help from a personal chef and trainer, in addition

to partnering with Weight Watchers.

With some hard work, Simpson dropped more than 50 pounds. Aside from chasing around her kids, she attributes her weight loss to a healthy diet and exercises four times

a week.