Beyonce Knowles swears by the Master Cleanse, Jaime Pressly lost her post-pregnancy weight by slurping cabbage soup and Brooke Shields and Kylie Minogue have been known to include a little grapefruit in their meals.

Ah, diets. From A-list celebrities preparing for the red carpet at a movie premiere to mere mortals who've got hot dates lined up in four days, women around the world have tried all kinds of regimens in a bid to lose a few pesky kilograms.

Blame pictures of skinny celebrities to unrealistic social expectations that have driven plenty of women to diets that promise quick results.

Karen Loh, 29, a civil servant who went on the Master Cleanse - a concoction of lemon juice, maple syrup and water with cayenne powder - for five days recently to prepare for her wedding, says: "I've tried many fad diets over the years but this has been the most effective. It's not enough to just look okay on your wedding. You have to be really thin to look good. Unfortunately, I've never been really thin but it hasn't stopped me from trying."

The soon-to-be bride, who weighed 67kg, lost 5kg in the five days by drinking this concoction and nothing else. She's since put on 2kg and plans to go on the diet again.

Created in 1941 by an American named Stanley Burroughs, the Master Cleanse is a detoxification diet but has been used by celebrities such as actress-singer Knowles and actor Jared Leto to lose weight.

But while you may have managed to shed a few kilograms, the real loser is your health, say doctors.

According to Dr Yeak Hwee Lee, a senior family physician and aesthetics practitioner at Raffles Medical Group, when we cut down on our food intake, our body is forced to burn its reserves - fat and muscles - for energy.

"In the short run, not eating enough will result in a lack of glucose and may cause hypoglycemia. You may be irritable, suffer from memory loss and, in extreme cases, faint," adds Dr Yeak.

It gets worse.

Dr Daniel Chan from ParkwayHealth Primary Care Network warns: "If your body uses too much of its reserves to try to meet its caloric requirement, it can be potentially harmful to your body and may even lead to organ damage, such as kidney damage."

Normally, the human body uses glucose, which comes from carbohydrates, to meet energy needs.

When it doesn't receive enough glucose, it turns to fat and protein.

The conversion of fat to energy is known as ketosis and results in a rise of ketone levels in the blood which can cause serious damage to our livers and kidneys.

There is no easy solution to weight loss, says Dr Chan.

"Some methods may work for some but not for others," he adds. "It boils down to eating sensibly and exercising. In some cases, medicine such as Xenical and Reductil may be helpful but these should be taken only after consulting a doctor."

The effectiveness of these drugs, which may cause side effects, have come under scrutiny recently. Xenical prevents the body from absorbing fat that is eaten, but may cause digestive and intestinal side effects. Reductil, which increases a patient's metabolic rate and causes him to feel full with less food, may cause a rise in blood pressure and pulse rates, and insomnia and nausea.

In general, combining a balanced diet with exercise is the simplest and most effective way in the long run to keep weight off.

Ideally, our diets should comprise 55 per cent carbohydrates (found in bread, cereal, rice and pasta), 30 per cent fat (found in butter, oils, margarine, sour cream and sweet desserts) and 15 per cent protein (meat, dairy, eggs and nuts) as well as two servings of vegetables and fruit daily.

Starving yourself for a few days will do more harm than good, according to doctors.

"You may end up bingeing after a few days because you've deprived yourself of food. Your weight may yo-yo and the sudden weight gain will only strain your heart," says Dr Yeak.

She recommends cutting down on your calorie intake in a healthy and balanced manner instead.

An average Asian man requires 2,000 calories a day while an average Asian woman requires 1,500 calories.

"In general, restricting your diet by 500 calories a day will mean that you lose about 1/2kg a week. This means you should be eating only two-thirds of what you normally eat," says Dr Yeak.

While she recommends that dieters cut down on their calories proportionately so they still cover the main food groups, she stresses the importance of vitamin supplements.

"You may not get all the vitamins you need when you restrict your diet."

Don't want to go hungry? Try upping your exercise regime while maintaining your diet.

The increased physical activity burns calories and fat and ups your metabolic rate, which is the rate at which your body converts energy stores into working energy.

It'll take more than a change in diet and a little exercise for most women to walk off the notion that being skinny is more important than being healthy.

"Somehow we've decided that the skinnier we are, the better," says Dr Yeak, "I'm surprised when I see women, who I think are slim, on restricted diets. Everyone wants to look like a model. But I think most people can be persuaded not to go on extreme diets."

Singaporean senior manager Claire Especkerman, 35, adds: "I suppose when you want to lose weight, diets are a shortcut to getting there but I've never believed in diets. I think it's important to eat healthy and exercise."

How hard is it to stick to a diet. Do they even work? Urban gets five Life! journalists to put five diets to the test.

Dieter: Lee Sze Yong, 28, 1.73m, 79kg

Diet: The reverse diet by American Tricia Cunningham works by encouraging participants to make breakfast their largest meal and dinner their smallest.

Weight loss: 2kg

DAY 1

I reckon I have the best deal - basically I just eat dinner for breakfast and breakfast for dinner.

But I soon realise that no zhi-char stall will open early enough for breakfast. No seafood fried rice for me, then. I settle on wonton mee and iced coffee.

Lunch is an hour late because of the heavy breakfast - most days I have just two slices of bread to start the day. I have roast duck rice with a hard-boiled egg and a cup of Ribena.

I have two slices of cheese bread with peanut butter and soy bean for dinner. Go to bed early because my stomach is growling.

DAY 2

I weigh myself. 1kg gone. So I reward myself with a fish burger meal from McDonald's.

I have a normal lunch - rice with vegetables, egg tofu and lemon chicken, and a glass of longan drink. I feel bloated but I want to brace myself for dinner.

Complete a 4km run. The military is kind to provide unfit men like me free physical training (code word: Remedial Training).

I am super hungry by the time I head to town to catch the movie Stardust. I gobble two slices of kaya toast, two eggs and a cup of tea before going into the theatre. The popcorn smells good. Luckily, Robert De Niro is funny enough to distract me.

DAY 3

Another 1kg gone. But it could be due to the previous day's run. My bowel movement is not great as I haven't been eating fruit. I probably worsen it by eating fried carrot cake for breakfast.

Lunch comprises a bowl of dry prawn noodles, two mini soon kueh and a glass of sugarcane juice. Yummy.

Dinner is a miserable big pork bun and a cup of Milo.

Despite the successful weight loss (so far), I doubt I will continue with this diet. I miss my steak at night.

Dr Yeak Hwee Lee says: There is a saying, "You should eat breakfast like a king and dinner like a pauper." This diet falls in line with that.

Breakfast should traditionally be your largest meal for the day and provide you with most of your nutrients.

Note, though, that it isn't a good idea to load your body with oily food first thing in the morning.

Your body needs food that is rich in complex carbohydrates such as bread and cereal to provide energy to get through the day.

Dieter: June Cheong, 25, 1.61m, 52kg

Diet: The Fish Soup Diet, as its name suggests, consists of fish soup. Fruit is also allowed. This diet is a variation of the Cabbage Soup Diet.

Weight loss: 0kg

DAY 1

Diets wreak havoc on your social life. You either become a tyrant - dictating where to have lunch or dinner - or turn into a recluse.

The first day is the hardest. I am reduced from a happy, carbohydrate-chomping omnivore into a hunger-stricken dieter with fantasies of dancing potatoes. And all in the swift course of one meal.

After having only water for breakfast, I look forward to a hearty lunch of clear fish soup and apples. But I am left unsatisfied, my stomach sinking into empty pits of deprivation. I catch myself foraging the dregs of my soup for scraps of fish skin or limp vegetable shreds, anything to fill that yawning void.

After work, I drag a few colleagues to a sushi chain where they scoff down handrolls, sushi, sashimi, deep-fried soft shell crab and fried tofu. Meanwhile I sit willing my seafood paper hotpot soup (okay, so I cheat a little) to bubble itself into edibility.

When I get home, I spy two boxes of Beard Papa delights. Feeling light-headed from a day of abstinence, I choose to nibble on a second-choice snack, an orange, instead. Sleep is a great comfort that night.

DAY 2

I awake from a rare, dreamless sleep. I conclude that the complex carbohydrates and what-nots I usually eat are what cloud my brain. This diet may work out after all.

Subsisting on a breakfast of water and fruit, as I have no fish soup handy, I head out to a lunch meeting. The catered delicacies include pineapple fried rice, green curry and red rubies with sago. The last vestiges of my resolve melt away and I spend the day tucking into rich Thai food, a bowl of soupy noodles, three Oreos dipped in milk, a cream puff and a chocolate bar.

DAY 3

I go back on the diet and have another bowl of fish soup for lunch. The hunger pangs are easier to withstand this time around and I congratulate myself on learning to function with a smaller calorie intake. Hari hachi bu (Japanese for eat until you are 80 per cent full).

I end up in another Japanese restaurant for dinner. And the rest, as they say, is katsu curry. As I wolf down the comforting concoction, surprising my dinner companion as I'm a renowned slow eater, I realise that this diet is prone to driving me to composing paens to potatoes and rice.

Dr Daniel Chan says: This may work for three days but it isn't sustainable in the long run. A successful diet must be well-balanced and sensible and this diet lacks carbohydrate and fat.

Dieter: Shaan Seth, 24, 1.69m, 54kg

Diet: The Master Cleanse Diet consists of a concoction of lemon juice, maple syrup and water with a little cayenne powder. The diet is used mainly as detoxification, but also by some just to shed kilograms. It is a purely liquid diet and no food is allowed. It was created in 1941 by an American named Stanley Burroughs and has been used by celebrities such as actress-singer Beyonce Knowles and actor Jared Leto to lose weight.

Weight loss: 1.5kg

DAY 1

The thought of surviving on a liquid concoction for three days makes me want to eat right away.

At first, it's exciting sipping my concoction - which has a great kick thanks to the excessive amounts of cayenne powder I add - but the novelty wears off, leaving me craving wonton mee, nasi padang and carbohydrates.

By 4pm, I succumb to my rumbling tummy and go to the staff canteen for a plate of mee rebus. Polishing it off only leaves me craving more, so I grab a curry puff.

Working late doesn't help and I leave my willpower behind to have dinner with colleagues at Sakae Sushi. I eat about eight plates of sushi and wash them down with two glasses of Coca-Cola. I resolve to do better tomorrow.

DAY 2

I get off to a strong start but running around in the afternoon for interviews brings back my hunger pangs.

By 2pm, my concoction seems as appetising as smelly socks and I treat myself to two doughnuts plus french fries.

The lack of glucose makes me cranky.

My tolerance for heat and long taxi queues diminishes rapidly and I find myself shooting dirty looks at people digging into plates of nasi briyani and mee goreng. I cheat (again) later and have a plate of rice with chicken and vegetables for dinner.

DAY 3

I have a croissant and coffee for breakfast.

A long day looms and cheating is relatively easy given the practice I've had already over the past two days. I manage to survive on lemon juice and maple syrup until 5pm when I give in and order mee goreng and two iced Milos.

Unless you're looking for a diet to put you off all diets and create a scary urge for anything fried or sugared, steer clear of this one.

Dr Daniel Chan says: This is not a sensible or sustainable diet. It lacks too many essential food groups to stay healthy.

Dieting should not be done at the expense of your health. I doubt this diet will help achieve any real weight loss or "cleansing".

Dieter: Suzanne Sng, 32, 1.63m, 50kg

Diet: The grapefruit diet has several versions. In general, dieters have half a grapefruit or about 240ml of unsweetened grapefruit juice with every meal. Meal plans, comprising meat and salad, are given, and a minimum quantity must be eaten. You eat until you are full. Diet usually lasts 12 days.

Weight loss: 1kg

DAY 1

I happily cook my breakfast of bacon and two eggs while sipping organic pink grapefruit juice. Very refreshing. The two slices of bacon allotted are surprisingly filling.

Lunch is roast chicken with salad. I drink a giant cup of grapefruit juice before eating and cannot finish even a quarter of a chicken.

Dinner is chicken soup with carrots and peas. Potatoes and onions - ingredients I normally put in my chicken soup - are forbidden. I down my giant cup of grapefruit juice before sipping more soup and end up feeling rather bloated.

DAY 2

More bacon and eggs. Yum. Tummy is now more used to the tang of the juice first thing in the morning, so it no longer feels acidic.

Lunch is leftover roast chicken from the day before with more greens.

At tea time, I happen to be at Kinokuniya book store and there is a delicious smell wafting in from the cafe. Almost succumb, but my willpower is strong enough to resist.

Manage to make it home for a late dinner of more grapefruit juice and chicken soup. Getting a wee bit sick of the taste of grapefruit.

DAY 3

Bacon and eggs for the third day in a row. The smell of frying bacon no longer thrills me. I long for toast.

Lunch is tuna salad. Unexciting but I chomp it down. Not very hungry, because drinking the big glass of grapefruit juice really bloats the stomach. Someone tries to tempt me with a gingerbread man, but I resist. No sugar and no carbo allowed.

Dinner is a steak with no sides. I finish up the last of my grapefruit juice. I am so sick of the taste and am already hallucinating about a huge pasta dinner the next day.

Dr Yeak Hwee Lee says: Having fruit or juice with every meal fills up your tummy and ultimately limits your intake of food. But the diet isn't very healthy and sticking to this in the long run will leave you with extremely high levels of cholesterol.

Doctors usually recommend just two eggs and three servings of red meat a week but this diet far exceeds this.

Dieter: Noelle Loh, 22, 1.65m, 48kg

Diet: The three-day diet is a low-calorie diet which started in the 1980s that promises significant weight loss. Strict meal plans are given and they comprise chicken, tuna, egg, fruit and limited treats, such as ice cream and peanut butter.

Weight loss: 0kg

DAY 1

The diet doesn't seem hard to keep to. I normally eat only two meals a day anyway.

For breakfast, I have toast with honey, as I don't have peanut butter at home, and some grapefruit juice.

I'm famished by noon. For lunch, I have half a tuna sandwich and a cup of black tea with two packs of sugar substitute. Very, very bland. Ugh.

Two hours later and my stomach is growling. I eat the rest of the tuna sandwich from lunch for fear of a gastric upset. I'm extremely hungry by 8pm, so decide to have a good meal and re-start the diet the next day.

DAY 2

I start the diet again. Toast with honey and a glass of grapefruit juice for breakfast.

For lunch, I have half a tuna sandwich and black tea with sugar substitute. I'm really craving something with a taste to it, so I get a can of Diet Coke. Respite.

One apple, as prescribed, while I'm out. I reach home at 9.30pm to have a slice of turkey ham and 250g of mixed greens, plus I have a glass of grapefruit juice (because I really need some sugar).

I make sure the one scoop of vanilla ice cream I'm allowed to have is a huge one. It's cheating but I'm starving. By midnight, my stomach hurts so I have five plain crackers and one boiled egg. Oops.

DAY 3

I'm surprised to find I'm down 2kg.

For breakfast, I have black tea, one soft boiled egg and toast. I have one banana as prescribed, and some leftover vegetables because I'm not full.

I'm out in town and can't resist the smell of freshly toasted baguettes from Delifrance so I have a tuna mayonnaise sandwich for lunch. Far from low cal, I know. I also grab a cup of black tea with sugar substitute. Guilty but happy.

For dinner, I have two medium-sized chicken frankfurters, 250g of mixed greens and a bottle of 100 Plus. Again I cheat and have one soft-serve ice cream cone because I just can't help it.

DAY 4

Forget the diet. I need to eat whenever and whatever I want. My weight is back to normal.

Dr Yeak says: This is a low-calorie diet that resembles starvation. It deprives your body of carbohydrates. Most of the weight loss might be due to water loss only. The weight probably won't stay off in the long run.