SummaryRead the full fact sheet
- 'Crash dieting' can affect your physical and mental wellbeing.
- There are no magical foods or ways to combine food that will help you lose weight.
- The best way to lose weight is slowly, by making small, achievable changes to your eating and exercise habits.
More Australians are overweight or than ever before, and the numbers are steadily increasing. Around 75% of men and 60% of women are carrying too much body fat and 25% of . This means that obesity-related disorders (such as and ), are also increasing.
No magic weight loss potion
There are many unhealthy misconceptions about . There are no magical foods or ways to combine foods that melt away excess body fat. To reduce your weight, make small, achievable changes to your lifestyle.
Understanding energy from food
Kilojoules in food
The macronutrients each supply a different amount of energy per gram:
- carbohydrate = 16kJ
- protein = 17kJ
- fat = 37kJ
- alcohol = 29kJ.
Fat and alcohol supply much more energy per gram than both protein and carbohydrates – a 35g slice of bread has about 360kJ while 35g of butter has 1062kJ of energy (almost 3 times as much as the slice of bread!).
Balancing energy needs
Our energy needs vary depending on factors such as:
Carbohydrates do not make you fat
Carbohydrates are essential for a well-balanced diet and healthy body. They are the body’s preferred energy source and fuel vital organs – including the brain, central nervous system and kidneys.
Carbohydrates are also an important energy source during exercise. The breaks down carbohydrates into glucose and the pancreas secretes a hormone called insulin to help glucose move from blood into the cells.
Eating a potato, a bowl of pasta, or any type of carbohydrate-rich food won't automatically make you fatter. In fact, the Australian Dietary Guidelines recommend 45 to 65% of energy needs to come from carbohydrates.
Some carbohydrates are healthier than others. have a slower and flatter blood glucose response. They take longer to digest and can help us feel full. Lower GI foods are less refined (or processed) such as , legumes and .
If you are on a low-carbohydrate diet, and cutting out large groups of , fruits and grains, you may not be getting enough vital nutrients to manage your weight effectively. These types of diets can increase your risk of micronutrient deficiencies and because of their low content.
Watch portion size and saturated fats
If you’re watching your weight, be mindful of the portion size of foods that you enjoy. A big serving of potatoes or pasta, served with high saturated fat butter, sour cream or creamy sauces will not help you lose weight.
Likewise, to , you need to be regularly eating more energy than your body needs. High-carbohydrate foods have about half the amount of energy of high-fat foods. When choosing high-carbohydrate foods such as grains and cereals, it’s best to choose wholegrain options. They will fill you up with fibre and provide additional health benefits.
Low carbohydrate diets - risks
There are many types of low carbohydrate diets – Paleo, Atkins, South Beach and Keto are just some. All of these diets restrict the amount of carbohydrate consumed to force the body to use protein and fat for fuel.
In the short term, very low carbohydrate diets can result in greater weight loss than high carbohydrate diets. But in the long term, weight loss differences appear to be minimal.
Very low carbohydrate diets can be unhealthy as carbohydrates are the preferred fuel source for our bodies to work effectively (especially the brain). If we restrict carbohydrates our and we may experience more mood swings than usual.
In addition, these diets increase our risk of kidney problems from having to process abundant protein (far more than the 15 to 25% of energy recommended to reduce disease risk).
And by cutting out large groups of vegetables, fruits and grains, these diets also tend to increase your risk of micronutrient deficiencies and constipation because of their low fibre content.
Short-term health effects of low-carb diets
The body begins to use stores of glucose and glycogen (from the liver and muscles) to replace the carbohydrates it is not getting from food. Around 3g of water is needed to release 1g of glycogen. Any weight loss at the beginning of a low-carbohydrate diet is mostly water, not body fat.
As carbohydrate stores are used up, the body begins to rely on other sources of fuel such as fat. This can lead to the development of ketones in the body, which can make the body acidic. It can also contribute to metabolic changes, which may be dangerous for some with certain conditions (such as diabetes).
Symptoms that may be experienced from a low-carbohydrate diet, include:
Long-term health effects of low-carb diets
The long-term health effects of a diet very low in carbohydrates but high in saturated fat is still uncertain. Further research is needed to determine the safety of these diets.
Possible long-term effects may include:
- Weight gain – when a normal diet is resumed, some muscle tissue is rebuilt, water is restored, and weight quickly returns.
- Bowel problems – restricted intake of antioxidants and fibre from fruits and vegetables can increase a person’s risk of constipation.
- Dieting problems – such as the ‘yoyo’ effect (where people lose and regain weight many times over a long period, rather than sustaining weight loss).
- , obesity and obesity-related disorders – diets high in protein and fats are associated with conditions, (such as heart disease, diabetes and ). This can occur if you have a diet high in fat, especially from fatty and processed meats (such as salami, sausages and bacon).
- – can occur in people with impaired kidney function or diabetes.
- and related conditions – due to loss of calcium from the bones.
Keto diet - risks
While many low carbohydrate diets focus on obtaining energy from protein, the Keto diet focuses on fat for fuel – contributing up to 90% of energy from fats (instead of the recommended 20 to 35% to reduce disease risk).
This means the liver must process extra fat so it could worsen an existing liver problem.
Also, the high amounts of saturated fat typically consumed in Keto diets increases the risk of elevated 'bad' LDL cholesterol and heart disease.
Because the long-term safety of these diets is unknown, seek advice from your doctor or a dietitian as there is likely a safer and more sustainable way for you to lose weight.
Single food diets don’t work
Plenty of diets are based on the belief that the digestive system can't process a combination of foods or nutrients. Commonly, carbohydrates (such as grain foods) and proteins (such as meat foods) are incorrectly thought to 'clash', leading to digestive problems and weight gain.
The opposite is often true – foods eaten together can help the digestive system. Such as, vitamin C in orange juice can increase absorption from a meal rich in plant-based iron like beans and rice, lentils and other legumes.
Also, very few foods are purely carbohydrate or purely protein – most are a mixture of both. The digestive system has enzymes that are perfectly capable of breaking down all the foods we eat so single food diets should be avoided.
Superfoods can’t help with weight loss
Fibre from food comes closest to having special dietary qualities, because it provides a feeling of 'fullness' with minimal kilojoules. High-fibre foods (such as fruit, vegetables, wholegrain breads and cereals and legumes) are usually high in nutrients and low in unhealthy fats.
The term 'superfood' gets used a lot but there is no standard definition of what a superfood must be. Most foods labelled as superfoods tend to be plant-based – acai berries, wheatgrass, spirulina, salmon, leafy greens, tea and turmeric. Although typically packed with nutrients – vitamins, minerals and antioxidants – they have little energy.
If you enjoy these foods and can afford them, there’s nothing wrong with having them as part of a healthy diet. But don’t expect to get huge health benefits by eating a couple of these with a poor diet. It is your overall dietary pattern that has the biggest impact on your health.
Skipping meals will not make you lose weight
It sounds simple enough – don’t eat and the weight will come off – but skipping meals can fail. Not only will starving yourself result in feeling tired and lethargic, your body is more likely to miss out on essential nutrients. Then when you do eat, you’re more likely to overeat and to make poor food choices. Over the long term, skipping meals is unlikely to help with weight loss at all.
The important thing to losing weight and keeping it off is to make small, achievable changes to your eating and exercise habits:
- Choose from a wide range of foods every day.
- Eat less-processed foods.
- Have a regular pattern of eating.
- Increase the amount you move each day to burn extra energy.
Intermittent fasting has been followed by various religions for centuries.
Fasting has gained popularity with the 5:2 diet, where for 5 days, people eat their usual diet and on the remaining 2 days, a very low energy diet is followed.
There are various versions of intermittent fasting, with some preferring to restrict energy on alternate days, alternate weeks or certain times of the day. (For example, following a 16:8 plan – fasting for 16 hours of the day and eating for the other 8 hours. Although this is considered ‘time restricted feeding’, it is still a version of intermittent fasting.)
Fasting overnight until your first meal the next day could also be called a form of intermittent fasting (break-fast).
Evidence shows there is generally no difference in the amount of weight lost by following a fasting diet when compared with a traditional energy restriction diet.
As with any diet, being able tosustain it is key to losing and keeping off weight. If following a strict intermittent fasting schedule doesn’t sound like something you could do for a long time, then this may not be the best way to keep your weight in check.
Eliminating foods will not lead to weight loss
Eliminating whole food groups from your diet won’t necessarily help you lose weight.
Unless you don’t like a food or choose to go for cultural, ethical or other reasons, eliminating animal products from your diet won’t help you lose weight. This is because you would need to reduce the overall number of kilojoules (energy) you’re having – just the same as a diet that has animal products.
Some research shows a healthy vegetarian dietary pattern, or a mainly plant-based diet, is associated with lower levels of obesity and reduced risk of health problems (such as and heart disease). But there are still many vegetarian food choices that can lead to weight gain, especially those that are high in fats and added sugars or if eaten in large amounts.
Going gluten-free for health is only for people with . If you haven’t been diagnosed by a health professional as having one of these conditions, then there’s no need to follow a gluten-free diet. By doing so, you may miss out on many of the vitamins, minerals and fibre from grains. And, if you’re choosing overly processed foods just because they’re labelled ‘gluten-free’, you may find you gain weight, especially if they’re lacking in fibre to fill you up.
Many drinks contribute to weight gain
Most other drinks have extra energy (usually from added sugars) without the health benefits of other nutrients. These include:
- soft drinks and slushies
- sports drinks
- flavoured milks
- packaged iced teas
- coffee made with full cream milk and flavoured syrup.
And if energy from drinks is not used by our body it will be stored as fat. There’s nothing wrong with enjoying these drinks occasionally as part of a balanced diet but the amount you have makes a big difference. For instance:
- Reducing a daily cola intake from 2 x 600mL bottles (2088kJ) to 1 x 200mL mini can (348kJ) = 25 teaspoons less added sugar per day.
Over a year, this small change could result in over 17kg of weight loss.
Alcohol has almost as much energy as fat
One ‘standard’ drink contains 10g of alcohol (or 290kJ). However, the size of a ‘standard’ drink can vary not only by alcohol percentage, but the amount of energy it has – such as a shot of alcohol mixed with tonic water or lemonade.
Also, when we drink alcohol our inhibitions tend to be lowered, making it more likely we will crave less healthy foods.
‘Clean’, raw or organic foods is not the solution to weight loss
Foods considered ‘clean’, raw or organic may be nutritious, but they may not be. There are benefits to choosing foods that are minimally processed. But there are also many other nutritious foods that will be missing from your diet if you eliminate whole food groups.
Be careful of products that claim to be organic. Although they might have been produced in an organic manner, this does not guarantee it’s a food that should be consumed regularly as part of a healthy lifestyle. If choosing organic is important to select a variety of foods that fit within the .
Science matters when it comes to weight loss
The amount of information available on food, diet and weight loss is endless and not much of it is credible or correct. Popular media is full of fad diets and magic weight loss potions endorsed by celebrities and supported by personal success stories.
Much of what is claimed is based on anecdotal rather than scientific evidence and, many times, there is something to be gained by the person or organisation behind the claim (such as profit from sales).
Unlike other fields where experts are trusted when it comes to nutrition and health, it seems that everyone is an expert.
While it’s true that we’re all different and what works for some may not work for others, proper scientific studies include a wide range of people – to account for individual differences.
If you would like to lose weight, a good start would be basing your diet on foods that fit within the . Or see a qualified health professional (such as a dietitian) who will give you dietary advice that is evidence-based, tailored to your nutritional and health needs and suits your lifestyle.
The key to weight loss
The best way to lose weight is slowly, by making small, achievable changes to your eating and exercise habits. Rather than being a slave to the number on the scales, be guided by your waist circumference – a is less than 94cm for men and less than 80cm for women.
Suggestions for safe and effective weight loss include:
- Don't crash diet. You'll most likely regain the lost weight within 5 years.
- Try to choose a variety of foods that fit within the .
- Be mindful of the portions you’re consuming – the bigger the serve, the more energy. (This is especially important for energy-dense foods and drinks such as those with high amounts of fats and alcohol.)
- Cut back on refined and added sugars.
- Increase your intake of fresh fruit, vegetables, and wholegrain breads and cereals.
- Cut back or eliminate empty kilojoules from sugary drinks and alcohol.
- Eat less takeaway and snack foods.
- Exercise for approximately 30 minutes on most days of the week. Introduce more movement into your day (such as a 30 minute walk).
- Don't eliminate any food group. Instead, choose from a wide range of foods every day and choose 'whole', less-processed foods.
- Have a regular pattern of eating and stick to it.
Watch your energy (kilojoule) intake
Ultimately, to avoid weight gain, energy intake should not be more than energy output.
Avoiding large portion sizes and limiting intake of saturated fats and added sugars will help to keep your energy intake in check.
Regular exercise is also critical for long-term weight loss success.
If you are not sure where to start or finding it difficult to manage your weight, seek help from a dietitian. Dietitians can guide you to a healthy way of eating that is based on the latest research and tailored to suit your health and lifestyle.
Where to get help
- , 2018, Australian Bureau of Statistics.
- , 2013, National Health and Medical Research Council, Australian Government.
- Headland ML, Clifton PM, Keogh JB 2020, '', International Journal of Obesity, vol. 44, pp. 1236–1242.
- Rynders CA, Thomas EA, Zaman A, et al. 2019, ', Nutrients, vol. 11, no. 10, pp. 2442.
- 2019, Harvard Health Publishing Harvard Medical School.
- 2017, National Institute of Diabetes and Digestive and Kidney Diseases, U.S. Department of Health and Human Services.