We are often sold promises of detoxing, losing so many pounds in as many days, or what the hottest celebrity diet is and how we can ‘look like them, too’, often, these fad or ‘crash’ diets are risky, unbalanced and harmful. It’s surprising to see so many fad diets still floating about, but with the diet industry estimated in excess of $470 billion, it’s no surprise (1).

What is a fad diet?

Fad diets are usually weight loss plans that promise quick and easy results but often lack scientific evidence to support their claims. These diets often have specific and restrictive rules about which foods can and cannot be eaten, and they may promise rapid weight loss without requiring people to change their overall eating habits or lifestyle (2).

While fad diets may lead to short-term weight loss, they are often difficult to stick to and may not provide lasting results. Many fad diets are overly restrictive and focus on eliminating entire food groups, which can lead to nutrient deficiencies and other health problems. 

Here are a few red flags that may indicate a diet is a fad diet:

1. Quick fixes or promises of rapid weight loss: Many fad diets promise quick and easy weight loss, often in unrealistic amounts (e.g. "lose 20 pounds in 2 weeks!"). While it is possible to lose weight quickly in the short term, sustainable and healthy weight loss typically occurs at a slower rate.

2. Magical claims about the fat-burning effects of certain foods or nutrients, or what foods are needed for each blood type. 

3. Lack of scientific evidence: Fad diets are often not based on solid scientific evidence and may not have been tested in rigorous clinical trials. Look for diets that have been studied and shown to be safe and effective.

4. Claims of ‘detoxing’ or ‘cleansing’ the body. Diets and products that claim to detox or cleanse the body are not evidence-based. Your liver and kidneys are your body’s tools for converting and removing waste products. 

5. Extreme or restrictive rules: Fad diets often require you to follow strict and unrealistic rules, such as cutting out entire food groups or eating the same foods every day (hello celery juice!). Diets that are too restrictive or eliminate entire food groups may not provide all of the nutrients your body needs to function properly.

6. Celebrity or influencer endorsements: While celebrities may be successful and popular, they are not necessarily experts in nutrition and the information passed down in the media may not be an accurate reflection. Be wary of diets that rely heavily on celebrity endorsements rather than scientific evidence.

7. One-size-fits-all all approach: Every person has different needs, requirements and circumstances, so if the diet is recommending specific calories for everyone then it’s not going to be taking into account your needs. 

8. Unsustainable in the long term: Fad diets are often difficult to stick to in the long run, as they often require you to make significant and unsustainable changes to your diet and lifestyle. 

9. Offering a sole alternative to important medical care, such as claiming to cure cancer. (2) 

In addition to being potentially unhealthy, fad diets may also lead to negative psychological effects, such as feelings of deprivation, guilt, and frustration. They may also contribute to disordered eating patterns and an unhealthy relationship with food.

There are many examples of fad diets, and new or rehashed versions seem to emerge all the time.

In this article, we will be looking at the types of fad diets that have been floating about this year:

Low-carb diets

Low carbohydrate diets have been popularised by celebrities and endorsed by some healthcare professionals as a way to lose weight and improve health. These diets involve minimising carbohydrate intake and focusing on high-protein and high-fat foods and often restrict or eliminate many nutrient-rich fruits and vegetables. 

Whilst there may be short-term weight-loss results with a low-carb diet, there is limited scientific evidence to support the maintenance of weight loss, and the impact of the diet on long-term health (3, 4). People who have been diagnosed with type-2 diabetes may have been advised to reduce their intake of carbohydrates, however, it is not recommended to cut these out completely (5). 

A more extreme version of a low carbohydrate diet is the Ketogenic or ‘keto’ diet; designed to switch the body’s energy system from carbohydrates to ketones. Ketogenic diets have been used as a potential treatment for children with epilepsy who do not respond to anti-seizure medication. Ketogenic diets should always be done under careful medical supervision (6). Medical supervision is advised because there are risks of severe health complications including kidney stones, osteoporosis and blood that is too acidic (ketoacidosis). Because of the reduced intake of gut-loving foods like fruits and vegetables, the impact of low-carb and ketogenic diets on the impact on the gut microbiota is also unknown (3 Wan). 

One large observational study and meta-analysis (a review of many research papers) found that both very high (>70%) and very low (<40%) intakes of carbohydrates were linked with increased mortality, the study found that people consuming 50-55% of their total energy intake from carbohydrates had the lowest risk (4Seidleman). 

Where possible, carbohydrate intake should be from whole grain sources (such as oats, wholewheat, rye and barley) as well as fruits and vegetables. These nutrient-rich sources help to provide a range of vitamins, minerals and fibre which are important for overall health and wellbeing. 

Carnivore diet

The carnivore diet is a dietary pattern that involves eating only animal products, including meat, fish, eggs, and sometimes dairy. This means that the carnivore diet excludes all plant-based foods, including fruits, vegetables, grains, legumes, and nuts.

Advocates of this ‘primal’ carnivore diet argue that it can provide a range of health benefits, including weight loss, improved mental clarity, and reduced inflammation. However, the carnivore diet is controversial and the evidence base is poor.

There are several potential risks associated with the carnivore diet, because it is very high in animal protein and red meat, it may increase the risk of certain health problems, such as increased risk of certain types of cancer (7) and mortality (8), in addition to short-term side effects such as bad breath, headache and constipation. The carnivore diet is low in fibre and important nutrients that are found in plant-based foods, such as: antioxidants, vitamins, and minerals. As with other fad diets, this may increase the risk of deficiencies and related health problems. 

Juice ‘cleanses’

Juice cleanses involve consuming only juice for several days in an effort to "detox" the body. Juice cleanses are often marketed as a way to lose weight and improve digestion. They are generally low in protein and may not provide the necessary nutrients for optimal health. Your liver and kidneys are well equipped for ridding your body of toxins - you don’t need fruit juice to do this. If juicing your fruit or veggies is the most convenient way for you to meet your 5-a-day then we support that - but we can’t endorse it as a meal replacement nor can we support the claims it will detox your body.

‘Detox’ teas

If a tea claims to be for slimming or ‘detoxing’, avoid it, or you may find yourself running to the bathroom. Many slimming teas claim to help you lose weight fast, but a quick look at the ingredients list may show things like senna, or similar laxatives and diuretics (a substance that causes increased urination) which can lead to water loss and diarrhoea. The weight loss comes from water and this may lead to dehydration.

Intuitive Fasting

Endorsed by some influential celebrities with large audiences, Intuitive fasting (9) involves severely restricting the window of eating, therefore reducing the amount of food consumed each day. This increases the risk of nutrient deficiencies and risky rapid weight loss, this diet plan does not have an evidence base for the claims made and with some fasting windows as long as 20-22 hours it can be seen to be promoting disordered eating behaviours - Red flag.

The risk of losing weight quickly

The rapid weight loss ‘promised’ by fad diets can seem appealing, however, it might lead to negative health effects such as nutrient deficiencies, dehydration, and electrolyte imbalances.

Losing weight too quickly can also cause the body to break down muscle mass instead of fat, which can lead to a decrease in metabolism (10) and make it harder to maintain the weight loss. Rapid weight loss can be difficult to sustain, and people who lose weight quickly are often more likely to regain the weight. Repeat weight loss and regain is called ‘weight cycling’ or yo-yo dieting which has been shown to be detrimental to psychological (11, 12) and physical health long-term (13, 14). 

A Healthful Lifestyle 

Now you’ve seen the red flags and may have decided that a crash diet is not for you. You may be wondering, “what can I do to improve my health?”

Firstly, you don’t need to lose weight to improve your health, a healthful approach could be to focus on balanced, nourishing meals that include a variety of whole, minimally processed foods to fuel your body. This may involve making small, gradual changes to your diet and lifestyle, rather than following strict rules. The Mediterranean diet is a good example of variety, and sustainability (15). and balance: consisting of healthy fats, whole grains, fish, plant-based proteins and lean meats 

Introducing regular movement that you enjoy such as walking, swimming or cycling can also support goals to be more heart-healthy (16), and improve lung function and mobility. 

It is important to remember that everyone's nutritional needs and preferences are different, and what works for one person may not work for another. If you are looking for support with your diet, arrange to speak to a healthcare professional such as a registered dietitian who will be able to make tailored recommendations to your needs and lifestyle.

Please note the information provided in this article is not a substitute for medical or dietetic advice. If you have any queries regarding your diet or your health, please speak to your GP or a registered healthcare professional.