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What is a ketogenic diet?

Does the hugely popular weight-loss regime really work?

ketogenic diet food on plate lead
Holly Enriquez
Holly Enriquez
Last updated: 01 June 2020

It seems everyone who's anyone is on the ultra low-carb ketogenic – or keto – diet. But is it safe? Does it work? And is it easy to stick to? 

To answer these questions – and with the added incentive of losing some extra pudge around the middle – I tried out the keto diet for two weeks.

CHOICE verdict

While the ketogenic diet may be an appropriate short-term solution under strict supervision for some, and it can result in weight loss, it could lead to serious health complications over time.

Going on the ketogenic diet made me realise I still held onto the belief that fats are the enemy. But good fats are vital for optimal health, so I'll be keeping the olive oil dressings and lashings of avocado in my diet, while definitely eating less bacon.

What is a ketogenic diet?

The ketogenic diet was developed as a treatment for epilepsy in 1924 by Dr Russell Wilder at the Mayo Clinic. Research has found the diet to be effective in reducing the frequency and severity of seizures in patients with severe epilepsy, but many people, including Hollywood's A-list, have adopted the extreme diet for quick weight loss.

The keto diet involves eating very small amounts of carbohydrates, medium amounts of protein, and getting most of your daily kilojoules from fats. Carbohydrates are the body's preferred source of energy. 

Ketones replace carbs as the body's main energy source, meaning it runs almost entirely on stored fat

When we starve the body of carbs, ketone bodies (or ketones) are produced by the liver from fat, and used as fuel for the brain and body. So on a ketogenic diet, ketones replace carbs as the body's main energy source, meaning it runs almost entirely on stored fat.

Ketones are also produced when your total kilojoule intake is low, because when you run short of stored energy your body will burn stored fat instead, resulting in weight loss. This process is referred to as being in the 'state of ketosis'.

eggs cooked in avocado keto diet

Avocado and eggs are popular keto-friendly foods.

What the expert thinks

According to Professor Clare Collins, an accredited practising dietitian and spokesperson for the Dietitians Association of Australia, there's a whole range of dietary approaches that come under that 'ketogenic diet banner'. 

"The classical ketogenic diet has a ratio of 4g of fat to 1g of combined carbohydrates and protein. So basically it's 85 to 90% fat, [which] isn't a palatable or exciting diet, as you can imagine, due to the massive restriction in types and quantities of foods that contain carbohydrates, including breads and cereals, fruit, some vegetables and even dairy products."

Professor Collins stresses that "the ketogenic diet should not be considered flippantly as something that anybody and everybody should be following. The individual needs to be under the supervision of a doctor and dietitian and be monitored for side effects, particularly if they're on medications."

What can you eat on the keto diet?

The keto diet limits carbohydrates to just 20–50g a day. A single slice of bread typically has 15g of carbohydrates, so you can imagine how restrictive this form of eating can be.

The diet – or popular adaptations of it that you'll find in books and on the internet – suggests consuming high volumes of animal products (so vegans and vegetarians may find this diet very difficult to follow) with a variety of the following foods:

What's in my trolley?

I fire up Uber Eats more than my stovetop, so this diet was a drastic change for me. Keto requires a lot of planning and preparation, which may be a deterrent for some. 

On day one I did a massive food shop, drawing inspiration from low-carb recipes I found online. My trolley was filled with meat (so much meat), cheese, butter and high-fat dairy – basically a lot of foods I don't normally allow myself. 

I also bought loads of the 'allowed' vegetables and fruits as nutrient deficiencies can occur on diets that are too restrictive. I also picked up a multivitamin supplement.

The biggest challenge of this diet was the lack of variety – and the enticing allure of carbs at every turn

The kilojoule-counter app MyFitnessPal helped me track how many carbohydrates I was consuming and kept my kilojoule intake in check. 

But the biggest challenge of this diet was the lack of variety – and the enticing allure of carbs at every turn. I was ready to throw in the towel on day four when a cafe owner refused to make me a bacon and egg roll without the roll. "What am I meant to eat?" I blubbered. In fact, studies in keto diets have found attrition rates are one of the highest challenges of the diet.

When starting the keto diet, people also report initially getting the 'keto flu' from eliminating carbs from the diet, with symptoms such as headaches, fatigue, brain fogginess and nausea. I didn't experience any major issues and actually felt quite sprightly (besides my aforementioned meltdown) during my first week on the high-fat diet.

Does the keto diet work?

After imagining I'd have a Biggest Loser-type reveal, after two weeks on the diet I was disappointed to find I'd only lost 1.5kg. But I was pleasantly surprised by the lack of hunger I experienced. For example, if I started the day with bacon and eggs, I wouldn't get hungry again till the afternoon, whereas my typical instant oats breakfast leaves me ravenous by 11am.

I was pleasantly surprised by the lack of hunger I experienced

A 2008 study published in the American Journal of Clinical Nutrition compared a medium-carbohydrate, high-protein diet with a low-carbohydrate ketogenic diet and found that after four to six weeks the 17 subjects lost significantly more weight and were less hungry on the ketogenic diet than the medium-carbohydrate diet. 

However, according to another study published in the American Journal of Epidemiology, low-carb diets were found to be no more effective than low-fat diets in the long term (more than one year).

Is the keto diet safe?

The most common side effect of the diet is constipation as a result of cutting out vital sources of fibre in the diet – fruits, vegetables, beans and grains. Lack of fibre can also increase the risk of bowel cancer and heart disease in the long term. I negated this by drinking lots of water, eating plenty of the high-fibre 'allowed' vegetables and taking a fibre supplement.

Other possible side effects of long-term adherence to the diet include:

  • raised cholesterol levels
  • renal stones
  • poor growth (in children)
  • reductions in bone density
  • altered immune function
  • altered liver function
  • nutrient deficiencies.

Although little research has been done specifically around the diet's long-term effects, some studies suggest there are health benefits in following such a strict low-carbohydrate diet, such as its ability to improve type 2 diabetes and shrink some forms of brain cancer. But more research on humans is needed and, as Professor Collins warns, this diet is used in medical nutrition therapy as a short-term test diet for specific medical conditions such as epilepsy and should only be used medically under the supervision of experts.

Professor Jennie Brand-Miller, professor of human nutrition at the University of Sydney says, "There's not a lot in the scientific literature to judge [the health effects of the keto diet]. On the basis of current science, I wouldn't recommend it. Several observational studies suggest this diet [actually] increases mortality, diabetes and cardiovascular disease."

For more information on how the ketogenic diet can help treat epilepsy, visit Epilepsy Action Australia.

Tips for sustainable weight loss

If you're looking for a sustainable weight-loss solution, Professor Collins says visiting your GP should be your first port of call.

"They will measure your blood pressure, blood lipids and blood glucose, and potentially look at kidney function and liver function," she says. "You should ask to be referred to a dietitian as well."

Your GP and dietitian will then assess your current state of health, weigh up the positives and negatives of different weight-loss regimes and recommend the appropriate one for you.

Rather than letting fad diets deprive your body of essential nutrients, simple lifestyle changes can help you not only lose weight, but also maintain it in the long term.

  • Go slow and steady – aim to lose 0.5–1kg a week. Any more than that and you're probably losing water and muscle, not fat.
  • Avoid high-glycemic index foods (sugary treats and highly-processed foods) – "They stimulate insulin secretion and drive fat deposition and they aren't as satiating," says Professor Brand-Miller.
  • Fill up on fruit and veg – they're bursting with phytonutrients and an analysis of three weight-loss studies of more than 130,000 adults found those who increased their intake of high-fibre, low-GI fruit and vegetables (your leafy greens over your stodgy potatoes) were more likely to lose or maintain weight.
  • Drink plenty of water – sometimes when you feel hungry, you're actually dehydrated, so keep a water bottle nearby to keep you hydrated during the day.
  • Up your exercise – according to a US study called the National Weight Control Registry, 90% of people who've lost an average of 30kg and kept it off for over five years exercise for an average of one hour a day.
  • Start the day with a healthy breakfast – that same study found 78% of respondents eat breakfast every day.
  • Watch your portions – eating from smaller plates can help keep portion sizes in check. A US study found that switching from a 10-inch to a 12-inch dinner plate (equivalent to switching from a 25cm to 30cm plate) caused people to consume 22% more kilojoules during a meal.
  • Experiment with herbs and spices – you don't need sugary dressings or sauces to add flavour. Try lemon, chilli, garlic, herbs and spices for heaps of flavour without adding kilojoules.
  • Cut back on ultra-processed foods and drinks – healthy wholegrain carbs are not the enemy, but junk food certainly is, says Professor Collins. "In Australia, one third of our total daily kilojoule intake comes from 'discretionary choices'." Always being prepared with healthy snacks is a great way to stop you from going to the vending machine mid-afternoon.
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