FAD Diets – are they worth it?

What is a FAD Diet?

A fad diet is an eating pattern or plan which is very restrictive including very few foods or an unusual combination of foods. The diets are encouraged to be followed for a short period of time in order to lose weight, promising rapid weight loss. However the reality of these diets are that they are not sustainable, involve a huge amount of restriction and can often result in more weight gain following the diet. These diets are often marketed as quick and easy fixes or solutions to health.

Why are FAD Diets dangerous?

While FAD diets may result in short term weight loss, improved insulin resistance and blood lipid profile in the short term, there are a variety of risks to be aware of too. These involve issues such as

How can you spot a FAD Diet

Being able to spot a fad diet is important to ensure you don’t waste your time, effort and money and also to protect your health. Common claims to stay away from include a diet that:

  • Promises rapid weight loss
  • Promotes eating mainly one food group
  • Cuts out a whole food group
  • Involves eating a small, extremely limited variety of foods
  • Encourages eating unusual combinations of foods
  • Recommends detoxing
  • Doesn’t have scientific evidence to back the claims made against the diet
  • Is endorsed by an individual that has no nutrition credentials or qualifications such as a celebrity
  • Focuses on appearance over health

The Alkaline Diet

This diet was first made popular in the UK when Victoria Beckham was reported to be a fan of it in 2013, followed by further celebrities including Gwyneth Paltrow. The basis of the diet is to remove ‘acid-forming foods’ and replace them with ‘alkaline -forming foods’. On the theory that disease stems from acidity in the body caused by food.

When we metabolise food, waste is produced as part of the process. This is what is said to be harmful by the promoters of the alkaline diet. However the mechanism has been highly criticised for being flawed. The body has an inbuild regulatory system including the lungs and kidneys, which keep the pH of blood very tightly controlled. It is not possible to change this with diet.


The paleo diet is based around diets followed by our hunter-gatherer ancestors. Although it’s impossible to know exactly what human ancestors ate in different parts of the world, researchers believe their diets consisted of whole foods. By following a whole food-based diet and leading physically active lives, hunter-gatherers presumably had much lower rates of lifestyle diseases, such as obesity, diabetes and heart disease. However, in todays world we are living in a different world. More time spent sedentary, easy access food and advances in technology mean we cannot apply the same diet and expect the same results.

Of course, eating whole-foods including fruits, vegetables, nuts, meat, fish and eggs is great. But having a long list of foods to ‘avoid’ including dairy products, vegetable oils, grains and legumes is problematic. There are also multiple benefits associated with consumption of foods such as dairy, pulses and legumes and wholegrains.

Weight loss in the short term may occur due to reduced calories and focus on food restriction, however there is a risk of nutritional deficiencies such as calcium and the weight loss is unlikely to be sustained due to the restrictions of the diet. Claims relating to disease prevention argued by advocates of this diet are also not substantial.  

The Grapefruit Diet

Originating in the 1930s, this diet is very limiting, promoting severe calorie restriction of 800-1000kcal per day. The plan involves eating grapefruit at every meal for 10-12 days and promises 10 pounds of weight loss in that time. The theory behind this is that grapefruit contains enzymes which help to ‘burn fat’ when consumed with food.

Dangers lie with this diet as certain drugs including statins may interact with grapefruit. In addition, there have been few studies to support the use of grapefruit in weight loss and losing 10 pounds in 10 days is a very rapid weight loss strategy which could be dangerous. The diet is also unsustainable, who could really eat grapefruit with every meal for the rest of their lives?!

What’s more, there is no evidence to support the idea that one food will help to ‘burn fat’. Losing weight is extraordinarily complex and involves a range of factors including sleep, lifestyle, genetics and physical activity. Suggesting grapefruit can instantly help to lose weight is very reductive.

Liquid Diets

Liquid diets and meal replacements come in various forms and are promoted for different reasons, mainly weight loss. These include juice diets, the cabbage soup diet and water fasting.

The premise behind juice diets involves consuming only juiced fruit and vegetables for 3-10 days, often promoted as a ‘cleanse or detox’. However it is not possible for a diet to ‘detoxify’ you’ve got your body for that! Your liver, kidneys, lungs and skin help you out.

No studies have investigated the cabbage soup diet, eating mainly cabbage soup for around 7 days. The thought behind the diet is that the lower calorie intake leads to significant weight loss and improves health.

Water fasting involves consuming only water for 24-72 hours and sometimes up to 5-7 days, potentially leading to severe malnourishment. While water fasting for a short period of 24 hours may have health benefits such as improvements in metabolic health reduce inflammation there is a lack of research in the area around impacts in the long term.

All three of these diets are very restrictive, may interact with medication and are not advised for individuals with health conditions such as type 2 diabetes, thyroid issues or kidney disease. They could additionally lead to nutrient deficiencies and unpleasant side effects such as bloating, cramping, dizziness, low energy levels and diarrhoea.

There are some medical reasons outlined for following a liquid diet, for example before surgery or for individuals with Chron’s disease. In this case the diet should absolutely be followed, under the supervision of a medical professional.

Raw food Diets

The raw food diet consists of avoiding any type of cooked food, consuming food only in its raw state such as vegetables, fruits, nuts and seeds. The diet is said to reduce development of disease and encourage weight loss. Following this diet comes with a great risk of food poisoning and toxicity and there is little evidence to support its effects. Risk of nutrient deficiency is high for this diet due to lack of animal products and limited food groups.

Unfortunately, anything which sounds too good to be true, most likely is. Fad diets can sound tempting as they offer quick and simple solutions to issues which are potentially long term, but they come with a host of side effects and can put health at risk. All of these diets also have one thing in common, restriction. But why can’t we focus on enhancing and adding to our diet and lifestyles, rather than always trying to remove something? Contacting your GP, a registered dietitian or nutritionist is your best bet for getting honest and evidence based answers about health concerns.

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