Are these 11 diet plans healthy or a fad?

The media is awash with claims about the best ways to lose weight, but do any of these diet plans provide a healthy balance? Dietitian Annemarie Aburrow debunks fad diets.

Battling the post-Christmas bulge is top of many people’s list of resolutions, and there’s no shortage of celebrity, fad and commercial diets promising an easy way to weight loss. Not all of these diet plans are healthy, particularly if you’re living with a long-term condition.

But maintaining a healthy weight and body shape is important for good cardiovascular health.

Here we explore popular diet plans and debunk some of the claims surrounding them.

1. Intermittent fasting

Salmon with broccoli

Dmitry Zuev / Via Flickr

Restrict your calorie intake for part of each day or week. The aim is to reduce overall energy intake and therefore lose weight.

What does a typical week look like? Fast day (twice a week):

  • Breakfast – one slice of toast with yeast extract spread (no butter or margarine)
  • Lunch – low-fat vegetable soup (no bread)
  • Dinner – salmon and broccoli; no snacking. Other days – eat as normal.

Diet debunked: The guideline daily energy intake is 2,000kcal for a woman and 2,500kcal for a man, although requirements vary depending on your age, physical activity levels and metabolism.

A healthy, sustained approach to weight loss requires control of your portion sizes and engaging in regular physical activity. Fasting may make you feel lethargic and less active, and you may be tempted to overcompensate on non-fasting days. For some people, fasting may create health risks, such as increasing the risk of low blood sugar in people with diabetes.

The more popular plans, such as the 5:2 diet, are essentially calorie-controlled diets. It’s roughly the same as reducing your intake to 1,600kcal per day, every day. There is some limited evidence that intermittent fasting leads to weight loss, but not much is known about its long-term effects. It won’t work if you overindulge on your non-fasting days.

Cost (in addition to usual foods): No additional cost.

Celebs who’ve tried it: Beyonce, J Lo and Miranda Kerr.

2. Eating like our ancestors

Roast beef salad 

Only eat foods available to our prehistoric ancestors, such as vegetables, fruits, nuts and meat, and exclude dairy products, grains, salt, pulses and processed foods. The paleo diet is one example.

What does a typical day look like?

  • Breakfast – steak and eggs cooked with coconut oil
  • Lunch – roasted butternut squash soup or a chicken salad
  • Dinner – beef stew cooked with blueberries, carrots and onion
  • Snack – boiled egg, prawns or nuts

Diet debunked: By excluding whole food groups, you risk deficiency in certain nutrients; for example, excluding dairy could lead to low calcium levels. Claiming these diets are prehistoric may also be misleading.

Evidence suggests cave people ate starchy carbohydrates and other foods ‘forbidden’ on the modern diet, depending on the season and where they lived. Some foods permitted on this diet wouldn’t have been available, including butter and coconut oil, which are high in saturated fat. Too much saturated fat may increase your risk of coronary heart disease and high cholesterol.

Why not try the Mediterranean diet instead? It’s also an ancient diet but there’s sound evidence it promotes heart health and weight loss.

Cost (in addition to usual foods): One study suggests it’s 9.3% more expensive.

Celebs who’ve tried it: Miley Cyrus, Matthew McConaughey.

3. ‘Sugar-free’ diets

Chicken thighs with roasted vegetables  

These cut out added white sugars and often ‘natural sugars’ (eg maple syrup or honey). Some versions cut starchy carbohydrates (eg pasta and rice), which the body converts to sugar, and fruits, which contain sugars.

What does a day look like?

  • Breakfast – poached eggs with avocado
  • Lunch – tuna quinoa salad
  • Dinner – chicken thighs with roasted vegetables
  • Snack – carrot sticks with cashew nut butter

Diet debunked: We’re all consuming too much sugar – free sugars include added sugars in food and drink, and the sugar in fruit juices. These account for around 12 per cent of UK adults’ daily energy intake, more than double the recommended maximum of five per cent.

The intake of children and teenagers is even higher. This can contribute to weight gain, which can lead to type 2 diabetes – two risk factors for cardiovascular disease (CVD).

Honey and syrups may be ‘natural’, but they’re still sugars. Dairy products and fruit contain sugars, but come with nutrients too, so it’s better to cut down on food and drinks with free sugars instead.

We don’t need to exclude starchy carbohydrates (pasta, bread and cereals), which should make up a third of our diets. These provide us with energy and maintain digestive health.

Cost (in addition to usual foods): May be cheaper due to the restrictions.

Celebs who’ve tried it: Davina McCall.

4. Slimming groups

Salmon and beetroot salad

Local groups with weekly meetings where an instructor weighs you and offers motivational advice. Some are online only.

What does a typical day look like?

  • You are given an allowance for different types of foods to guide your meal choices each day.
  • No foods are banned, but healthier choices mean your allowance goes further.
  • Most vegetables are ‘free’ so you are encouraged to eat plenty of them.

Diet debunked: The NHS sometimes refers people to slimming groups. Their strong focus on calorie counting and portion control (both sound principles) can encourage sustained weight loss. The aim is to make it simpler for people to limit their calorie intake while allowing occasional treats, which is a sensible long-term approach.

The support of others may help, too. However, many also offer ‘add-ons’ such as ready meals, snacks and breakfast bars. It is healthier (and cheaper) to cook from scratch or swap a snack bar for a portion of fruit, which will also help you towards your 5-a-day. And although slimming group products are calorie-controlled, they may be high in salt.

Cost (in addition to usual foods): Joining fee (around £10) and weekly group fee (around £20-25 per month).

Celebs who’ve tried it: Oprah Winfrey, Jessica Simpson.

5. High-fat or high-protein diets

Eggs with bacon 

cyclonebill / Via Flickr

Reduce carbohydrate intake and increase intake of fat and/or protein to compensate. This reduces overall calorie intake and can induce ‘ketosis’ – a state where the body breaks down fat into ‘ketones’ to provide energy, causing rapid weight loss.

What does a typical day look like?

  • Breakfast – bacon and fried eggs
  • Lunch –  a burger with salad instead of a bun
  • Dinner –  steak with broccoli

Diet debunked: While you may lose weight quickly at first, there’s no evidence that these diets are any more effective than others in the long-term. High-fat diets can be unhealthy, too. While fats are important, too much fat will unbalance the diet.

We need to ensure we’re including the right types of fat (unsaturated fats like olive, sunflower or rapeseed oil and nuts). Take care if you’ve got high blood pressure; processed meats like bacon and sausages can mean the diet is high in salt.

High-protein diets may also increase your risk of kidney damage and osteoporosis. Due to the low carbohydrate intake, bad breath can be a problem, along with other side effects like fatigue, dizziness, insomnia and nausea.

Fruits, vegetables and wholegrain carbohydrates should make up two-thirds of your diet, with only 12 per cent from protein-rich foods like meat, fish and dairy products. Eight per cent of your diet should come from foods high in fat and sugar, such as butter, oils and cream.

Cost (in addition to usual foods): Can be significantly more expensive depending on your choice of meats, fish and fruit.

Celebs who’ve tried it: Kim Kardashian, Sharon Osbourne.

6. Juicing

A glass of cucumber and apple juice 

bertholf / Via Flickr

A short-term diet consisting entirely of fruit and vegetable juices. Often advertised for ‘detoxing’ as well as weight loss. Juices can be made at home or bought pre-made from a commercial company.

What does a typical day look like?

  • You will consume only fruit and vegetable juices for a short period of one to five days.

Diet debunked: These diets are not nutritionally balanced. You’ll miss out on important nutrients like calcium and protein. Side effects include fatigue, headaches, diarrhoea and bad breath. Drinking only juices is likely to make you feel hungrier, too.

When fruits are blended into juices, it causes the ‘natural’ sugars, which are incorporated into the cellular structure of the fruit, to become ‘free’ sugars, which are more likely to have a negative effect on dental health and weight.

Fruit juices should be limited to one small glass a day (150ml) and fruit or vegetable juice only counts as one of your 5-a-day, regardless of how much you drink.

Juicing, even for a short time, could be dangerous for people with certain pre-existing conditions. For example, if you have diabetes, too much fruit juice can raise your blood sugar.

People taking certain medications should also be careful: grapefruit juice can interact with statins and calcium channel blockers, and cranberry juice can interact with warfarin.

Cost (in addition to usual foods): Companies charge around £140-£200 per week. If making own juices, allow £30 - £100 for juicer, and £30-£70 a week for fruits and vegetables.

Celebs who’ve tried it: Katie Price.

7. Low GI diet

Porridge with berries on top 

‘Glycaemic index’ (GI) is a scale that assigns a value to carbohydrate-rich food based on how much it increases blood sugar levels. Foods with a lower GI (like vegetables and pulses) release sugar more slowly, providing a steady supply of energy, helping you feel fuller for longer.

What does a day look like?

  • Breakfast – porridge with berries
  • Lunch – mackerel and chickpea salad
  • Dinner – chicken and white bean stew, with baked apple for dessert

Diet debunked: Following a low GI diet that includes plenty of fruits and vegetables and lower GI versions of carbohydrates (eg, swapping high GI breakfast cornflakes for low GI porridge), and that limits intake of foods and drinks high in sugar and fat, can be a healthy, sensible and balanced way to lose weight.

Most GI diets also focus on reducing fat intake (especially saturated fats). However, don‘t get too caught up in the numbers – milk chocolate and ice cream have a low GI, but this doesn’t make them healthy.

Similarly, rice cakes have a higher GI than chocolate but are much lower in calories. Combinations of foods affect the GI of a meal. Some low GI plans encourage ‘phases’ of dietary restriction, which could cause you to miss out on key nutrients.

Cost (in addition to usual foods): No significant costs.

Celebs who’ve tried it: Bill and Hillary Clinton.

8. Meal replacements

Meal replacement shake 

danlev / Wikimedia

Manufactured products replace regular meals. Companies selling the plans promise quick weight loss. The diet works by limiting calories. Some are termed ‘very low calorie diets’, providing less than 800kcal per day. These should be followed for no more than 12 consecutive weeks and under medical supervision.

What does a day look like?

  • Specially manufactured products, like shakes, soups and bars, replace most of your meals.

Diet debunked: The rapid weight loss can be motivating, but many people revert to old eating patterns and put weight back on afterwards. While meal replacements often contain added vitamins and minerals, some are high in salt and saturated fats.

These programmes come at a cost of £120 to £200 a month. They are restrictive when it comes to family meals and eating out, and reported side effects include fatigue, diarrhoea, constipation and nausea.

Cost (in addition to usual foods): Around £120 - £150 per month.

Celebs who’ve tried it: Adele.

9. Wheat free / dairy free

Lentils salad 

Whilst some people need to follow a special diet for medical reasons, there is a growing trend for people to go ‘gluten-free’, ‘wheat-free’ or ‘dairy-free’ to help them lose weight.

What does a typical day look like? These can vary as they are about what is out rather than in. Gluten-free would mean:

  • Eating meat, fish, dairy, fruit and vegetables, rice, potatoes and lentils.
  • Cutting out bread, pasta, pizza, cakes, biscuits and cereals (though gluten-free versions are available), as well as most beers and some ready-made foods.

Diet debunked: Whilst coeliac disease is a medical condition where people must avoid gluten for life, wheat and/or lactose intolerance is a grey area. If you have an underlying wheat or lactose intolerance, this diet may improve symptoms of bloating and other gastrointestinal niggles.

However, you should speak to a GP about this, and never self-diagnose an allergy or intolerance. Any weight lost using this approach is probably due to consuming less food and therefore fewer calories, or because you’re cutting out foods like cakes and pastries (which come with lots of fat and often sugar), rather than any negative aspects of wheat or dairy themselves.

You may find yourself eating more fruit and vegetables, whilst avoiding processed foods and decreasing your sugar and fat intake. Remember to include wholegrain carbohydrates, as they help control appetite, by making us feel fuller for longer. If you do have diagnosed wheat intolerance, be sure to replace wheat-based carbohydrates with alternatives like oats, rice and suitable wholegrain breads.

Cost (in addition to usual foods): Wheat-free version of products like bread and pasta are more than double the cost of regular products.

Celebs who’ve tried it: Gwyneth Paltrow, Victoria Beckham (gluten-free).

10. Food combining

Chili con carne

These bizarre diets are based on the principle that different foods require different acidity to be digested properly, and all have different transit times through the gut.

Combining certain foods (eg. carbohydrate and protein) together in one meal is thought to make it harder for the body to digest them. This supposedly reduces absorption of nutrients, and slows down the time food spends in the gut, promoting the build-up of gas and toxins. Sometimes foods are classified into acidic, alkaline and neutral.

What does a typical day look like?

  • Breakfast – spinach with eggs
  • Lunch – avocado and pine nut sandwich
  • Dinner – chilli con carne (no rice)
  • Snack – fruit only on its own

Diet debunked: These diets are based entirely on pseudoscience. It is nonsense to suggest that carbohydrates can’t be digested in an acidic environment; after all the stomach is acidic itself! We digest different nutrients at different rates and the body has adapted to an omnivorous diet over the years.

If you’re diabetic, these diets are not a good choice because eating protein and fat together with carbohydrate in the same meal reduces the effect of the carbohydrate part of the meal on blood sugar levels. Certain nutrients may be absorbed better when they’re eaten in combination with healthy fats.

Cost (in addition to usual foods): No significant costs.

Celebs who’ve tried it: Liz Hurley.

11. Single food / food group diets

Grapefruit in a bowl 

Rebecca Sims / Via Flickr

These are diets which restrict you to one food group only, or one type of food only. Common examples include the cabbage soup diet or grapefruit diet.

What does a day look like?

  • The same thing for every meal, every day.

Diet debunked: These diets are very strict, boring and repetitive, and may leave you craving other foods. There are many reported side effects, including bad breath and diarrhoea. These diets require lots of planning and cooking separate meals from the rest of the family.

If you are on certain medications for diabetes, you may be at risk of hypos because of the severe calorie restriction. If you are on statins or calcium channel blockers, beware of the grapefruit diet as this may interact with medication.

In the short term, these diets can cause quick weight loss, simply due to the severe calorie restriction. However, because these plans are so short term (usually seven days), this weight loss will mainly consist of water and muscle loss, rather than fat loss.

Cost (in addition to usual foods): Cheaper due to the restrictions.

Celebs who’ve tried it: Kylie Minogue, Dolly Parton, Sarah Michelle Gellar.

But what is a balanced diet? 

The eatwell plate is a visual representation of a healthy, balanced diet. It shows that a third of your diet should be fruits and vegetables, a third wholegrain carbohydrates, and a third lean protein-rich foods and reduced-fat dairy products.

Avoid too many foods high in fat and sugar. To lose weight healthily, maintain these proportions, but reduce your portion sizes. This way, you eat fewer calories while still getting the nutrients you need.

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