Diets exposed: What works and what doesn't

Our experts rate 12 popular diets and share invaluable advice to help you lose weight - for good.

The promise of rapid weight loss is hard to resist but while many diets work in the short-term, few result in lasting weight loss.

What doesn't work

Low-kilojoule diets

Examples: The Cabbage Soup Diet, the Grapefruit Diet and the Chicken Soup Diet.

What they are: Low-kilojoule diets which restrict the types of foods and the amount of food you can eat. Some of them are based on a single food, such as cabbage or grapefruit.

Why you lose weight: The weight reduction is due to the extremely low kilojoule intake.

The pitfalls: Whole food groups are excluded, which can result in malnutrition. With any diet providing less than 3360 kilojoules (800 calories) a day, your body will react as if it’s being starved, meaning it will conserve energy (i.e. fat) and start to break down protein (i.e. muscle) instead. When you finish the diet, your body will try to replenish its energy stores, so you tend to regain weight rapidly.

Bottom line: These diets are nutritionally imbalanced and so are unsustainable and potentially harmful in both the short- and long-term. They can also cause you to regain more weight than you lost as breaking down muscle mass slows your metabolism.

Meal replacements

Examples: Celebrity Slim, Slim Fast, Tony Ferguson, Fat Busters and Optifast (see note).

What they are: Instead of ‘proper food’ for lunch you just make a shake or a soup from a packet. Sometimes, these meal replacements are all you eat.

Why you lose weight: They restrict kilojoule intake, so if you stick to them, you will lose some weight.

The pitfalls: Meal replacements may help as a quick fix but they don’t address the real problem, which is changing your eating habits and lifestyle. They don’t teach you about healthy eating, so as soon as you stop taking them, you revert back to your old eating patterns and the weight creeps back on.

Bottom line: These are quick-fix diets that more often than not result in weight gain.
Note: Optifast is an exception when taken as part of a particular program that is supported by health professionals and teaches healthy eating habits. This program is only available for people with a BMI over 30 or over 27 and at least one risk factor for disease.

The detox diets

Examples: Lemon Detox Diet, Liver Cleansing Diet and Raw Food Diet.

What they are: Based on the premise that we can get rid of toxins that build up in our bodies and ease the load on our lymph system, kidneys and liver.

Why you lose weight: There is no evidence to support the theory of detox – only your liver and kidneys can rid your body of toxins. However, some detox diets are essentially based on fruit, vegetables and wholegrains so you feel better and lose weight simply because you’re making better food choices.

The pitfalls: Some detox diets restrict major food groups so you miss out on essential vitamins and minerals. Others – like the Lemon Detox Diet which involves fasting and using a drink made with lemon juice – are extreme and potentially dangerous.

Bottom line: If you do feel better on a ‘detox diet’, you probably haven’t been eating a balanced diet previously and your body is just enjoying the wholesome foods.

Food combining

Examples: The Hay Diet, Fit For Life and the Biogenic Diet.

What they are: Developed by Dr William Hay almost 100 years ago, they are based on avoiding eating proteins and carbohydrates together, and allowing at least four hours between eating the two nutrients.

Why you lose weight: If you do lose weight, it’s simply because you’re eating less food overall, due to the complicated nature of meal structure and the difficulty of including snacks.

The pitfalls: This diet is difficult to sustain and has no scientific backing. Weight is lost because the amount of food you eat is below desirable levels, but you could be missing out on important nutrients.

Bottom line: Food combining is a gimmick, based on old and incorrect scientific principles. Some of our most important food sources – such as dairy products, breads and cereals – contain the perfect combination of protein and carbohydrate, and our digestive system can digest any combination of food.

High-carb, low-fat, high-fibre

Examples: F2, F-Plan Diet, the Mayo Clinic Diet and the Pritikin Diet.

What they are: These diets follow the principle that high-fibre foods fill you up – without the kilojoules.

Why you lose weight: Of all the ‘fad diets’, this one most closely resembles healthy eating principles, encouraging you to eat lots of vegetables, fruit, grains and pulses. Fat intake is also limited.

The pitfalls: The low-fat versions of this diet – such as the Pritikin Diet – can lead to the over-restriction of foods that provide essential nutrients, such as lean meat, fish and low-fat dairy products. The high-carbohydrate content may lead to bloating in some people, while others may eat too many refined carbohydrates such as cakes and biscuits.

Bottom line: This is one of the healthier types of fad diets, but some can be a little extreme. High-fibre foods are promoted by dietitians but it’s important you still get adequate protein and healthy fat, while keeping refined carbohydrates to a minimum.

Low-carb diets

Examples: Atkins, South Beach, The Zone and the Montignac Regime.

What they are: These diets focus on restricting carbohydrates to varying degrees.

Why you lose weight: Depriving your body of starchy foods like pasta, bread and rice causes it to use up glycogen (glucose) stores, the first and main fuel source. This results in rapid weight loss initially, but most of this is water. As restricting carbohydrates does reduce kilojoule intake, you will eventually start to burn fat.

The pitfalls: In the absence of carbohydrates, fat or protein is used as an energy source and this can cause unpleasant side effects such as headaches, tiredness, mood swings and bad breath. The low level of fibre can lead to constipation. This diet is also high in fat, most of which is saturated.

Bottom line: Rapid weight loss does occur but it is rarely maintained. It is usually rapidly regained as soon as you start eating cabohydrates again.

What does work

Calorie-counting diets

Example: Weight Watchers.

What they are: Programs based on healthy eating and calorie control, using a points or calorie-counting system. Exercise and physical activity are included in the program. There is a lot of support and you can learn from other people’s experiences.

Why you lose weight: Weight Watchers doesn’t tell you exactly what to eat but provides education, dietary advice and support. Exercise is promoted, too.

The pitfalls: The hardest thing is to expand your knowledge of food and calorie content. It’s impractical to always count calories so it’s important good eating habits are learned.

Bottom line: Weight Watchers has continued to stay up-to-date and offers more flexibility with its plans. It provides motivation and support, and rewards you when you reach your goal weight. No diet program will work for everyone, but Weight Watchers does empower you to take control of your eating and exercise habits so you can make lasting changes.

High-protein, mod-carb diets

Examples: CSIRO and CSIRO 2.

What they are: These diets are high in protein (but not to the extent of Atkins) and low in fat. There are plenty of vegetables and fruit, as well as substituting bread with lentils and beans. They are based on protein providing a satiety effect, so you eat less overall.

Why you lose weight: These diets include everyday foods that people love and provide delicious recipes. They also work on portion control and protein intake, both of which assist weight loss.

The pitfalls: These diets can be expensive to follow, especially if you have to feed a whole family. The amount of protein is also higher than recommended by nutritional bodies. And there is no support offered – you just follow the diet in the book.

Bottom line: The first CSIRO diet was criticised for its lack of exercise, so an exercise plan was included in the second version. This style of ‘dieting’ is great for teaching healthy eating habits, but can be too high in protein.

Low-GI diets

Examples: The New Glucose Revolution (there’s a whole range depending on your condition).

What they are: Originally developed to manage diabetes, low-GI diets focus on eating low-fat foods and carbohydrates with a low GI (which produce a slow, steady increase in blood sugar levels). The amount of high-GI foods are limited.

Why you lose weight: These diets encourage you to eat plenty of foods with a low GI, thereby controlling blood sugar levels, keeping you feeling fuller for longer, providing you long-lasting energy and reducing mood swings.

The pitfalls: It’s difficult to work out the GI of a meal, as the GI system is based on individual foods. Also some foods that are low-GI are packed with fat or salt and contain few nutrients.

Bottom line: These diets teach you about foods and how they affect your blood sugar levels and your body. In general, most dietitians are supportive of this style of eating plan.

Low-salt, high-carb, high-fibre

Example: DASH Diet.

What they are: This diet is designed to lower blood pressure, but can also be used to lose weight. The DASH Diet is low in total fat, saturated fat, salt and cholesterol. It emphasises fruit, vegetables, wholegrains, low-fat dairy products, poultry, fish and nuts. The diet reduces consumption of lean red meat, sweets, added sugar and sugar-containing beverages.

Why you lose weight: This diet incorporates the basic healthy eating guidelines that focus on eating whole foods and minimally processed foods.

The pitfalls: This diet has more fruit, vegetables and wholegrains than you may be used to eating. It’s high in fibre, so can cause bloating and diarrhoea in some people. To avoid this, it helps if you increase these foods gradually.

Bottom line: The DASH Diet is recommended by reputable organisations such as the Australian Heart Foundation and the American Heart Association. It’s a healthy diet, which also emphasises regular exercise.

Prepared meals

Examples: Lite ‘n’ Easy.

What they are: Prepared meals are delivered straight to your home, so you don’t need to think about preparing breakfast, lunch or dinner. Dietitians ensure the meals are low in fat and portion sizes follow the healthy eating guidelines.

Why you lose weight: Portion control is what helps this program to work. All meals take into consideration the Australian Dietary Guidelines and provide essential vitamins and minerals. Regular exercise is also promoted as part of the program.

The pitfalls: When you stop buying the prepared meals, you may revert back to your old eating habits, which may include large portion sizes, irregular meals and high-kilojoule foods. They also don’t teach you healthy cooking practices.

Bottom line: This program does promote healthy eating, portion control and regular exercise, but may not teach you the principles of healthy eating. Try to learn these principles during the program.

Weight-loss clinics

Examples: Jenny Craig, Sure Slim.

What they are: At Jenny Craig, you meet with a counsellor, purchase Jenny Craig products and attend weekly weigh-ins. With Sure Slim, you choose a program based on a blood test to see glucose and insulin levels, medical history, lifestyle and food preferences. This is followed by weekly sessions with trained consultants.

Why you lose weight: Weight-loss clinics provide you with tailored programs and offer you ongoing support. Jenny Craig uses products specifically made for weight loss.

The pitfalls: On Jenny Craig, the food can get expensive and may only be sustainable for a short period of time. You’re also eating food that is different to the rest of your family. Sure Slim promotes quick weight-loss programs, which is not the best way to lose weight.

Bottom line: These programs may be expensive to maintain long-term. Better to learn the principles of healthy eating and regular exercise.

10 expert tips to help you lose weight

1. Make changing your lifestyle a priority

Make a commitment to achieving a healthier lifestyle. But don’t try to change everything at once. Start gradually. Next time you meet friends for drinks or coffee, go for a walk with them instead.

2. Make a plan

Develop your own healthy eating plan. Don’t call it a diet. Remember that the diets you followed in the past have not worked, so it’s time to do something different. Aim to make lifelong changes.

3. Set yourself milestones

Make your goals SMART (specific, measurable, achievable, realistic and time-based). Your goals can be small such as avoiding your morning muffin. Achieving any goal, no matter how small, will always put you in a more positive frame of mind!

4. Eat foods you like

Write a ‘green’ list of all the healthy, nutritious foods you like. You may be surprised how long the list is. Then write a ‘red’ list of foods you like which are high in kilojoules and less nutritious. Plan how to increase the amount of green foods in your diet and reduce the reds. Reduce the red foods gradually so you don’t feel like you’re depriving yourself.

5. Change your thinking

Ignore that little voice in your head that can be extremely negative. Change your thinking; turn the thoughts from “I can’t” to “I can”. Keep reinforcing your positive thoughts – practice makes perfect.

6. Create some rules

Create healthy living rules, but make them positive. Don’t say, “No eating at my desk”; say “I will always eat food away from my desk”. Write down your rules and place them in a spot where you will see them regularly. And respect your rules.

7. Seek support

You don’t have to go it alone. Seek support from friends or even attend support groups such as Weight Watchers. You could also visit a dietitian. Whichever method you choose, have someone to report to, so in your moments of weakness they can help you get back on track. Or even better, follow a program with a friend or family member so you can support each other.

8. Move your body

You need at least 30 minutes of physical activity each day. So wherever and whenever possible, be more active. Take the stairs instead of the lift. Walk to the shops instead of driving. Also add some structured exercise into your day such as walking, cycling or going to the gym.

9. Keep a food diary

Record all the foods and times you eat, and be sure to include those little extras. Seeing what and how much you eat can make it easier to see the habits and times of the day that you need to be particularly careful. Keep a food diary for as long as you like.

10. Designate your time

Set aside some time during the week that is all about you – no work, no kids, no chores, no stress. Yoga, going for a walk, having a bath or even reading the newspaper on the balcony can all help to reduce your stress levels and bring the focus back to you. These, of course, are just a few of the activities you could do – the list is endless.

Real-life success stories

Craig Erskine-Smith, 53, dentist
Starting weight: 103.5kg
Weight lost so far: 16.5kg

What motivated you to lose weight?
I’d been putting on about a kilogram a year for the past 20 years. When I turned 50 I became more aware of my health and I started getting serious about my weight.

What was your diet and exercise regimen like before you started?
I ate without much thought. I worked long hours, would skip breakfast, usually eat a small lunch and then come home late at night and eat a big meal. I felt I deserved a reward for working so hard so I would indulge in my favourite foods.

How did you get started?
I read about the concept of ‘energy density’ – how some foods have a high kilojoule count while the same-size serve of another food can contain much fewer kilojoules. For example, I could eat a bowl of pasta in five minutes or a huge bowl of ‘hearty’ salad in 20 minutes, which would fill me up more, give me more flavours and nutrients and fewer kilojoules. So I started to count the kilojoules in everything I ate and I read the nutrition panel of packaged foods and started comparing different foods.

Describe your diet and exercise regimen now?
I can describe it in two words: salads and stir-fries. I have big portions – I eat till I’m full so I don’t feel like I’m missing out. As for exercise, I try to walk regularly.

What advice would you give someone trying to lose weight?
Write down everything that you eat and work out how many kilojoules it contains. I guarantee it will change the way you eat. I would also stress that food should always taste good. Don’t eat special ‘diet’ products that taste like cardboard – cook yourself real food and lots of it. Eating should be a pleasure so be creative.

Tina Kiz, 35, is a strength and conditioning coach.
Starting weight: 116.2kg
Weight lost so far: 34.2kg

What motivated you to lose weight?
It was a combination of my state of mind and my physical health. I knew if I didn’t do anything it would affect my happiness and future.

Describe your lifestyle before you started.
Years ago I was very fit and healthy. However, due to a back injury, life choices and relationships, I went down a path of huge weight gain, panic attacks and loss of self-confidence, which in turn led me to eat more and very rarely leave home.

You’ve tried to lose weight before; why did you finally succeed this time?
This time, I pinpointed situations in my life that made me over-eat – times when I was unhappy or bored. I try to take responsibility for my life, to make the right decisions and healthy choices. No-one else can do that! It is hard sometimes, but you have to be honest with yourself, ask the hard questions and if need be, ask for help!

How did you get started?
My life reached a boiling point and in a sense, I exploded! I started eliminating everything bad or negative in my life. It was one very slow step at a time. Some days it was five steps back and one step forward.

What help did you have while losing weight?
My family, especially my mum and dad, gave me a lot of support in every way.

How did you stay motivated?
For the first few months it was sheer determination and my family’s support and faith in me. I started to notice small but positive changes; I started to have faith again and knew where I wanted to be in my life.

Describe your diet and exercise regimen now?
I love to cook my own food and it costs less. I eat five to six meals a day. I eat lots of fruit (apples are the best) and vegies, power salads, wholegrains (brown rice, oats and rye), milk and plain yoghurt. Lots of tuna and seafood (salmon/prawns), chicken breast and small amounts of lean red meat. I love legumes and beans. If I want to splurge, I do and I never deny myself any craving. I do cardio exercise every day (30 minutes to 1 hour), including taking my dog for a walk and a swim at the beach. I also love doing weights 3 to 4 times a week. When I need to rest, I do. On my rest days, I try to watch what I eat a bit more.

When did you feel you had achieved your goal?
My journey is still continuing as I do have a bit more to lose, and most of all to learn, but I feel like a winner.

How do you stay on track now?
I limit temptations at home and around me. Other people like their chocolates or ice-cream but I try to have a good fruit salad and yoghurt or a handful of fruit and nuts. The more healthy your diet, the less your body craves rubbish. There are so many healthy choices now.

What weight-loss advice can you offer others?
Start with small steps and they will become great ones. Read the labels – know what you are eating. Get up and go for a walk – now! Also, it’s okay to indulge sometimes.

Kym Reeve, 37, is married and has three children. She recently became a Weight Watchers leader.
Starting weight: 105.5kg
Current weight: 60kg
Total weight loss: 45.5kg

What motivated you to lose weight?
I had been diagnosed with type 2 diabetes, my blood pressure was high and I felt tired all the time. But I finally got serious when we moved into our new house with a large bathroom mirror – I would catch my reflection every morning on hopping out of the shower and I wasn’t happy with what I saw.

Describe your lifestyle before you started.
I hated fruit and vegetables. I lived on bread. I drank a lot of cordial and did as little exercise as I could. I always had second helpings and picked at food all day.

You’ve tried to lose weight before; why did you finally succeed this time?
I’ve spent most of my life trying to lose weight in one way or another. At times I would resent having to think about it so much so I would stop and these were the times of greatest weight gains. I made lots of little changes to my lifestyle and they gradually became part of what I did day-to-day. I also feel I was successful because I committed to following the Weight Watchers program – going to the weekly meetings was an invaluable experience.

How did you get started?
I tried for two weeks to do it on my own but found that every day I would make an excuse and decide to start again tomorrow. I knew that to be successful I would need to commit to something. So my mother and I joined Weight Watchers.

What help did you have while losing weight?
Weight Watchers provided me with a food plan that was easy to follow and got me exercising by starting out small and building up. I had a lot of support from my family and friends.

How did you stay motivated?
Weight Watchers breaks down larger weight losses into smaller chunks, for which you get little rewards – working towards those really motivated me. Attending the meetings helped as well – I found it a good way to refocus my efforts if things had gone a little astray. Having the commitment of weighing-in each week kept me motivated. I also read about others who had lost the same amount or more weight than me and that really helped. Having my mother come with me and doing the program as well was great. And I had reminders of my weight-loss goals around the house.

Describe your diet and exercise regimen now?
I have maintained my weight for nearly four years now and I still follow the Weight Watchers program. It keeps my portion sizes in check. I eat a good balance of all the food groups. I drink lots of water and diet soft drinks. I go for regular walks. And I try and be active every day – with three boys that’s not too hard to do.

What weight-loss advice can you offer others?
A great time to start is now! If you wait for the perfect time it may never come. Incorporate the changes into your life; make it something you just do. It’s not always easy to stay on track, but it’s worth it to feel so healthy and happy.