By ASHLEY PEARSON

Last updated at 14:33 13 March 2008

Nowadays, it's hard to find much body fat in Hollywood.

Today's stars are slim and toned, whittled to within an inch of their lives.

When pressed about their slimming secrets, celebrities often rave about their "good genes", their affection for junk food, or declare that their secret to staying thin is simply running around after their children.

But here's what you should know: a lot of them are lying.

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Slim stars - LEFT: Paris Hilton CENTRE: Lindsay Lohan RIGHT: Britney Spears

Shaping up: Angelina Jolie worked with Gunnar Peterson, who has dished the dirt on how stars achieve their figures

Celebrity trainer Gunnar Peterson, who has trained Angelina Jolie, Jennifer Lopez, and Penelope Cruz, says: "I had one actress training with me four times a week in addition to daily exercise bike classes.

When the Press asked how she'd 'transformed' her body, she said: 'Oh, I do yoga and hike with my dog.' It makes me laugh."

So the next time you see a pin-thin celebrity bragging about her relaxed approach to eating, remember this:

They take drugs

When Lindsay Lohan was arrested on suspicion of drink-driving, police said they found cocaine in her pocket.

Paris Hilton recently admitted to U.S. talk show host Larry King that she takes Adderall for attention deficit disorder.

Both drugs are often used by women looking to lose weight. Hollywood's party girls always seem to have access to certain drugs known to help shed pounds.

At the moment, Adderall is the latest diet drug craze in Hollywood, and the number of celebrities addicted to it continues to rise.

Just about every female celebrity arrested - from Paris to Nicole, from Lindsay to Britney Spears - has had prescription Adderall in her handbag. It keeps you awake while killing the appetite.

For the jet-set, hard-partying girl it has become the miracle pill - one, however, with potentially dangerous consequences.

Even when taken as instructed, Adderall can cause psychotic episodes, depression and serious heart problems.

Eating disorder expert Carolyn Costin, who has treated many Hollywood actresses, says she's even seen a rise in "the drugs used for attention deficit being crumpled up and snorted".

Some celebrities also take Clenbuterol, known as "Clen". Commonly prescribed to treat respiratory problems in horses, in humans it can cause fat loss.

While Clenbuterol and Adderall create a slimming effect in the short-term, after a while, users report a sudden and uncontrollable weight gain. Having tampered with the natural metabolism, the drugs stop working.

Manhattan-based trainer Justin Gelband, who works with catwalk and catalogue models, says: "Diet pills and steroids are huge right now. After Kate Moss was caught supposedly doing coke, the modelling agencies started to crack down on girls using hardcore drugs like cocaine and heroin to stay slim.

"So now it's more diet pills and steroids; they are easier to hide and, if pressed, the girls can say that they have a prescription."

They eat nothing but boiled eggs

During the filming of Cold Mountain, there were rumours that one famous actress on set ate only boiled eggs.

She would rise in the morning and eat one and then have one or two at the end of the day. That was her entire diet.

And apparently she is not alone.

Celebrity trainer David Kirsch says: "I had a client who was getting ready for the Oscars and all she ate was one meal a day - of two boiled eggs! I was able to persuade her to add some almonds and a protein shake and some vitamin supplements.

"It's a self-defeating strategy, you need to eat enough, and particularly protein, to build lean and toned muscle in the first place."

They fast

Paris Hilton caused a stir when she walked into New York restaurant Nobu recently.

When a waiter asked the heiress for her order, he was quietly told: "Mineral water."

In fact, over the course of her two-hour "meal", Paris took sips of water and Red Bull - she didn't eat a single bite.

And she's not alone. Super-slim Desperate Housewives star Marcia Cross was spotted dining at a restaurant a few years back with her now husband Tom Mahoney.

Lifelong battle: Marcia Cross describes not eating is 'a constant struggle'

According to one eyewitness: "He ordered sea bass and prawns, but she just sipped fruit juice."

Marcia recently admitted to the pressure to be thin: "Not eating is a constant struggle. It's like they pay me not to eat. It's a living hell."

Then there's the master cleanse, otherwise known as the lemonade diet: water mixed with maple syrup, lemon juice and cayenne pepper.

Beyonce admitted following it for two weeks to drop one-and-a-half stone for the film Dreamgirls, and Jared Leto used it to shed the two stone he'd gained to play Mark Chapman in the film Chapter 27.

Gunnar Peterson calls it the "You're an idiot" diet.

"I had a client who did it and I thought he was ill," says Peterson.

"His skin was grey and his eyes had terrible dark circles under them. He was shuffling when he walked, and this was after only ten days!"

One of Hollywood's dirty little secrets is the "IV diet", in which celebrities check themselves into hospital to get put on an IV so they can avoid eating altogether.

Peterson says of the IV diet: "This is beyond ridiculous. If you're doing this you're not fat, you're crazy!"

Suzanne Peck is the director of programmes at Homefield Grange Retreat, a cleansing spa in the UK that relies on juice-fasting.

She says: "Fasting is designed to rest the digestion, hence allowing clarity of thought, cleansing of toxins and healing of the body in general; not to fit into a size-zero dress."

They abuse laxative teas

Britney Spears has never been shy about her love for junk food and engages in all kinds of behaviour to counteract her taste for Taco Bell.

She smokes, drinks coffee and Red Bull, has diet pills in her bag and takes Adderall. She has also been seen hitting all-night drugstores, shopping for laxatives.

And she is certainly not alone.

Today, many actresses are taking laxatives in the form of "dieter's tea", which has a mild laxative effect. Some starlets are drinking up to ten cups a day.

Trainer Gelband says: "The latest trend among models is mixing laxative tea with the master cleanse diet. All they drink is master cleanse and laxative tea."

Such a drag: Katharine Heigl smokes regularly, a well known way of suppressing appetite

They chain-smoke

Grey's Anatomy star Katherine Heigl looks to have lost a stone in the last year.

She may be following a healthy eating plan, but she appears to have a secret weapon - she smokes constantly.

A few days ago, the beautiful blonde was spotted having lunch in Los Angeles. She ordered just a salad, but spent the meal chain-smoking.

Nowadays she is rarely photographed without a cigarette in her mouth, and when she isn't smoking, she is clutching a pack.

Marc David, nutritional psychologist and author of The Slow Down Diet says: "It's a choice, really. You are choosing possible lung cancer and death over treating your body with respect, all in an effort to be slim."

They eat peanuts

Supermodel trainer Gelband admits: "I had one girl who was living on Diet Coke and peanuts. She drank three to five Diet Cokes a day and ate a big bag of nuts. If she got hungry, she smoked.

Her eyes had huge bags under them and she looked wasted. When we tried to work out, we had to stop every five minutes. It was awful."

They guzzle caffeine

Paparazzi shots regularly show Hollywood's skinniest actresses, such as Renee Zellweger and Mary-Kate Olsen, sporting giant sunglasses and regularly coming out of Starbucks clutching gigantic cups of coffee.

This is a trend in Hollywood, where many believe coffee not only speeds up their metabolism but also keeps them from eating.

"One client I had would eat almost nothing all day, she just drank coffee constantly," says trainer to the stars Peterson.

"She'd have some lettuce in the afternoon, and drink coffee instead of dinner. Working out was a waste of time because of the state she was in."

Marc David says: "Coffee and caffeine can actually make you fat. If you're drinking too much, the caffeine mimics the stress response in our bodies and your cortisol and insulin levels rise. These elevated levels of stress hormone signal the body to store fat."

They wear a patch

Peterson says: "I had one guy using a Nicorette patch, not to quit smoking but to stop food cravings! This is a ridiculous approach and definitely won't work."

Gym bunny: To prepare for her role as Daisy Duke, Jessica Simpson worked out for two hours a day, six days a week

They live at the gym

Who can forget those photographs of a skeletal-looking Teri Hatcher jogging through Hollywood with weights in both hands and bones protruding-through her skin?

Actress Kate Hudson, in a quest to shed the five stone she gained while pregnant with son Ryder, admitted to working out up to three hours daily for three months.

To prepare for her role as the sexy Daisy Duke, Jessica Simpson worked out for two hours a day, six days a week.

Justin Gelband says: "You can get addicted. Unless you're a professional athlete, you don't need to do more than one-and-a-half hours a day to get a great result."

Amber Kenain, general manager at Crunch gym in Hollywood, a celeb favourite, told Glamour magazine: "There's one singer-actress who works out at my gym for about five hours a day, even on weekends. She spent her birthday here."

Peterson admits: "To be fair, a lot of the top women are doing the right things: eating healthy and exercising, but not obsessively. It's the up-and-comers who I see going to crazy extremes."

He adds: "Forget trying to look like a celebrity - look at you.

The reality is, the girl that's ten pounds overweight but loves her body is winning against the girl who is underweight but hates herself.

"There's no straight guy in the world who knows the difference between a size 14 and a size 4."