Nutritionist ranks the most popular diets from best to worst – and it’s bad news if you are a fan of keto or paleo

  • Nutritionist Sophie Scott ranks popular weight loss diets from best to worst 
  • She rated five diets – including keto, paleo and CSIRO – on a scale of one to 10
  • The nutrition trainer looked at which diets actually work and which to avoid 

Nutritionist Sophie Scott (pictured) has ranked the popular weight loss diets from best to worst

A nutritionist has ranked the popular weight loss diets from best to worst.

Sophie Scott, the head nutrition trainer of FIAFitnation, rated five diets – including the trendy keto and the modern-day ‘caveman’ eating style – on a scale of one to 10.

She examined Mediterranean, intermittent fasting, CSIRO, paleo and keto to see which diets actually work and the ones that don’t.

‘An analysis of popular diets shows that restrictive diets are generally ineffective in the long term because when food is suddenly limited, energy expenditure is reduced and when people become less active, energy use in cells is slowed, which can limit weight loss,’ she explained.

‘Increased hunger also ensues, so that once the restriction ends, more food is eaten than prior to the restriction until the earlier weight is attained. Dieting is also the number one risk factor for developing an eating disorder.

‘While dieting will always be popular, the cornerstones of good health should always be exercise (at least half an hour per day) and a varied diet full of whole, unprocessed foods, as well as the occasional treat.’

The ketogenic diet is a low carb, high fat diet that has gained popularity as a weight loss diet over the past five years. It focuses on cutting out carbohydrates but filling up on fatty foods to lose weight (stock image)

What you need to know about the keto diet

  • Eliminates many foods, such as from the fruit and vegetables, dairy, and grain food groups
  • Carbohydrate-containing foods, such as breads, cereals, rice, pasta, legumes, fruit, and starchy vegetables (like pumpkin, peas, and potato) must all be limited
  • Not aligned with recommended number of serves for each food group
  • Low in fibre
  • Early research indicates keto can cause havoc on gut health


The ketogenic diet is a low carb, high fat diet that has gained popularity as a weight loss diet over the past five years.

It focuses on cutting out carbohydrates but filling up on fatty foods to lose weight.

‘Keto forces the body to use fat (or more specifically, ketones) as the main fuel source instead of glucose,’ Sophie explained.

‘Carbohydrates are severely restricted to around 50g per day (equivalent to two slices of bread and a banana) and fat constitutes 70 per cent of this diet.’

The diet encourages followers to eat butter, avocado, coconut, bacon, cream, cheese and some nuts but avoid grains, milk, yoghurt, most fruits, legumes, potatoes and many vegetables.

According to the Dietitian’s Association of Australia, keto diet isn’t recommended for the general population as the long-term efficacy and safety of the diet are unknown, having only been studied in the short-term.

Rating: 2/10


Paleo, or the ‘caveman diet’, mimics the foods eaten by our hunter-gatherer ancestors

Known as the ‘caveman diet’ that mimic the foods eaten by our ‘hunter-gatherer ancestors’, Paleo eliminates grains, beans, legumes, dairy, refined sugar and processed foods  and oils.

The style of eating focuses on high intake of quality protein such as grass-fed meats, fish, eggs, seafood, limited fruits, healthy fats such as nuts and seeds and oils (olive, flaxseed, macadamia, avocado, and coconut) and fresh fruits and vegetables. 

‘Critics suggest that it is nonsensical to follow a diet like our predecessors for a number of reasons; the types of food available now are vastly different to what was available then, the human genome has had time to adapt to eating other foods such as grains and there is not one hunter-gatherer diet,’ Sophie said.

She pointed out that while the diet eliminates two important food groups – dairy and grains – paleo reduces sugar and processed foods.

Rating: 3/10 

The downsides to intermittent fasting

  • Significant reduction in calories (less than half or a quarter) compared to recommendations on some days
  • Risk of nutrient deficiencies on fasting days (e.g. you could eat 500 calories on a fasting day by having a slice of chocolate cake and a glass of milk only)
  • Involves counting calories which is not promoted within the guidelines
  • Some people find training performance suffers when fuel is insufficient


Intermittent fasting is a dieting method where you restrict what you consume at different times of the day or the week, followed by a period of regular eating.

There are a number of different options available – the most popular of which is the 5:2 approach, which means you consume a total of 600 calories (2510 kilojoules) for men and 500 calories (2090 kilojoules) for women – and fast two days of the week.

‘Proponents claim intermittent fasting results in rapid weight loss, mental clarity, improved sleep and increased energy,’ Sophie explained. 

‘However, research indicates there is no significant difference in weight loss between intermittent fasting and continuous calorie restricted diets in the short or long term.’

But she pointed out there are evidence that suggests intermittent fasting regimens are ‘not harmful physically or mentally in healthy, normal weight, overweight, or obese adult’.

Rating: 6/10 if the diet includes whole foods and minimal processed foods.


The CSIRO Total Wellbeing Diet focuses on protein-rich foods, healthy fats, wholegrain breads and cereals and lots of vegetables

The CSIRO Total Wellbeing Diet, which is backed by science, is a high-protein, low-fat, moderate-carbohydrate (low GI) diet (40 per cent kilojoules from carbohydrate rich foods).

The consumption of meat is recommended – beef, lamb or veal four times a week for dinner, plus fish and chicken or pork three times a week.

‘While no food group is excluded, the focus is on including protein-rich foods, healthy fats from fish and oils, wholegrain breads and cereals and lots of vegetables,’ Sophie explained. 

‘Critics of the diet argue that it promotes the consumption of large amounts of red meat and other animal product and high red meat intake has been associated with and increased risk of some cancers.’

‘Studies show this diet does result in slow steady weight loss, however no more than a higher carbohydrate diet.’

Rating: 7/10


Tong touted by health experts as the secret to a lengthy, healthy life, the Mediterranean diet promotes an ‘approach to healthy eating’ (stock image)

What is a Mediterranean diet?

There is not one Mediterranean diet, but the diets of the people living in the 16 countries that border the Mediterranean Sea share common aspects:

  • High intake of plant-based foods
  • Core foods enjoyed every day: whole grains, fruits, vegetables, beans, herbs, spices, nuts and healthy fats such as olive oil  
  • Twice weekly servings of fish and seafood
  • Moderate portions of dairy foods, and occasional poultry Infrequent servings of red meats and sweets
  • Low in red meat, sugar and saturated fat 
  • Rich in phytochemicals, antioxidants and fibre 
  • Focus on fish consumption over red meat 25-40% of total energy comes from fat (focusing on olive oil) 
  • Eggs consumed four times per week 
  • Wine and coffee consumed in moderate amounts

Tong touted by health experts as the secret to a lengthy, healthy life, the Mediterranean diet has been crowned the healthiest nutritional plan for promoting an ‘approach to healthy eating’.

It’s rich in fruit, vegetables, wholegrains, legumes and olive oil, and features moderate amounts of fish and poultry – and the occasional glass of red wine.

The diet eliminates added sugars, refined grains like white breads and pasta, trans fats like in margarine, canola oil and processed meat.

‘The diet is more of an eating pattern, rather than a prescriptive diet, which makes it easier to follow consistently than other more restrictive diets,’ Sophie said.

She referenced a research that found the diet consistently performs well in relation to weight loss, reduction in cardiovascular disease and reduction of depression.

The PREDIMED study, published in the New England Journal of Medicine in 2013, showed the Mediterranean diet group had a third less heart disease, diabetes and stroke than the low-fat group. They also lost a little weight and had less memory loss.

‘The benefits can’t be narrowed down to one single food or factor but to some general themes,’ she said. 

‘Extra fibre, a diverse range of fruits and vegetables, whole grains and legumes, yoghurts and cheese, small amounts of fish and meat, red wine, nuts and seeds and good quality olive oil all played their part.

‘However, the authors believe that the olive oil itself was the most powerful single factor.’

Rating: 10/10 

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