5 of the most extreme diets (and what they could do to your body)

When you choose a diet, it’s important to think about more than whether it will help you fit into your favourite jeans. Some diets can have serious health consequences if followed long-term, as our dietitian explains.

1. Juice diets

A glass of cucumber and apple juice 

bertholf / Via Flickr

These involve consuming only the juices of fresh fruit and vegetables; usually for a minimum of three days. You can make your own juices or buy pre-made juices through various companies.

These diets are not nutritionally balanced. By only eating fruits and vegetables, you will miss out on energy from carbohydrates, protein, essential fats, and minerals like calcium.

You can tell that these diet plans are unhealthy because the companies promoting them only recommend their plans for short time periods. If you do lose weight using this approach, most of this will be water and muscle, rather than fat, and this weight will quickly come back once you restart normal eating.

If you go on a juice diet regularly, you could become anaemic and your bones could suffer through lack of calcium. If you have diabetes, juicing can be dangerous; the large amounts of fruit juice involved can affect your blood sugar control and your HbA1c levels.

Side effects are likely, including low energy, fatigue, headaches, diarrhoea, constipation and bad breath.

2. Raw paleo diets

Lamb and Beef Carpaccio

Alpha / Via Flickr

The paleo diet approach involves replicating the supposed hunter-gatherer-style diets of our ancestors during the paleolithic period. There are many different versions, but they often exclude beans, legumes, starchy carbohydrates, starchy vegetables and dairy products.

Eating meat raw places you at higher risk of food-borne diseases

However, there is no agreement amongst historians about the exact diet these early ancestors consumed, with some experts believing milk and grains were a part of their diet towards the end of the paleolithic period. One of the most extreme versions is “raw paleo” in which only uncooked foods are allowed.

Because so many foods are excluded, these diets are unbalanced and cannot be recommended. Excluding dairy products will make it difficult to get enough calcium in your diet, leaving you at risk of developing osteoporosis later in life. Eliminating beans, legumes and starchy carbohydrates (like rice and pasta) from the diet may leave you low in fibre (increasing your risk of constipation) and B vitamins.

Another concern is that paleo diets often promote saturated fats like butter and coconut oil, and large amounts of red meat. Eating too much saturated fat increases the amount of cholesterol in your blood, increasing your risk of developing coronary heart disease. Eating too much protein (as it often the case with this approach) can also take its toll on the body. Long term excess protein intakes have been linked with osteoporosis and kidney disease.

Eating meat raw places you at higher risk of food-borne diseases. Also, cured but uncooked meats, such as salami, are advocated on some paleo diets. Processed meats tend to be high in salt, and have also been linked with bowel cancer.

3. Sugar free diets

Chicken thighs with roasted vegetables  

There are many versions of this diet around, varying from those advocating the avoidance of sugar and starchy carbohydrates, to those advocating the elimination of any natural sugars in fruits and dairy products too.

Whilst decreasing the amount of sugar you add to food and reducing your sugary food and drink intake are national recommendations, to eliminate all sugar and carbohydrates from the diet is not only realistic, but unhealthy.

Avoiding starchy carbohydrates may leave you at risk of anaemia and constipation, as well as fatigued and low in energy. Cutting out dairy products without substituting them with calcium-enriched alternatives may leave your bones at risk of osteoporosis.

Avoiding fruit is not a good idea; we know that consuming five portions of a variety of fruits and vegetables a day is good for heart health, and protective against cancers.

  • Read more about getting your 5-a-day.

4. Single food diets

Grapefruit in a bowl 

Rebecca Sims / Via Flickr

Often the latest fad or celebrity craze, these very restrictive diets allow you to consume only one food group or one type of food. Some examples include grapefruit or cabbage soup only.

Regardless of what you may read, there is no one food (or food group) on the planet that can provide all the nutrients you need for health. These diets are therefore not recommended, not even short term.

Any weight loss you do experience is likely to be water and muscle loss rather than fat loss anyway! If followed long term, serious damage could be sustained, such as anaemia and osteoporosis.

General side effects will usually include low energy, fatigue, irritability and bad breath. Depending on what you’re avoiding, constipation, diarrhoea or flatulence could be rife.

5. Food combining

Chili con carne 

There are many types of food combining diets, but they all require you to combine certain groups and avoid certain combinations. For example, pasta and green vegetables might go together, but a spaghetti bolognaise (meat and carbohydrate) would not.

The theory behind food combining is to do with the acidity of certain foods, and the body’s supposed ability to digest certain foods combinations. There is no evidence that these diets improve digestion or stimulate weight loss.

Due to the strict difficulty of following these types of diet and lack of evidence to support them, we would not recommend this approach. With careful planning, it may be possible to achieve a balanced intake of foods overall across the day.

However many of these diets make it difficult to include a good dairy intake, meaning you could be at risk of osteoporosis due to reduced calcium intake if followed longer term.

If you’re diabetic, eating a meal containing healthy fats and protein-rich foods in addition to carbohydrate reduces your post-meal blood sugar levels. Food combining diets don’t mix carbohydrate and protein, meaning your blood sugar control could go haywire.

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