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As ‘keto’ diet books hit the shelves and the #zerocarb and #keto hashtags go viral, nutritionist Matt O’Neill asks, how healthy are these diets and are they a wise choice for weight management?

Ketogenic diets are very-low carbohydrate diets (often as low as 5 per cent of daily calories or 20 grams of carbohydrate a day) and very high in fat (up to 75 per cent of calories). Protein makes up the difference at a moderate 20 per cent of calories.

With so little carbohydrate, the body is forced into a state known as ‘ketosis’ in which fat stores are broken down into ketones to fuel muscles and the brain.

While ketogenic diets have been used clinically for decades to help treat epilepsy by reducing seizures, they are now getting mainstream attention as a nutritional strategy for cancer treatment, for reversing of type-2 diabetes and for ultra-endurance performance.

The attraction of rapid fat loss and keto-adaptation to become a better fat burner is attractive to fitness enthusiasts. But going keto requires some serious dietary effort. To keep carbohydrate intake under 20g per day, you’ll need to eliminate whole food groups, including grains, fruit, dairy and any starchy vegetables. Even semi-starchy vegetables, like carrots, beetroot and tomatoes, may need to be limited.

Questions about keto diets

The restrictive nature of ketogenic diets raises a lot of questions.

Keto advocates say we don’t need to eat carbohydrate, but can your body run normally with little-to-no carbohydrate – on ketones – and still be healthy?

Does keto mean steak and bacon for breakfast, lunch and dinner is OK, as the memes on social media suggest?

Can such a restrictive diet meet all your nutrient needs? Which vitamins, minerals and phytochemicals could you potentially go short on?

What is the impact on gut health? Will cutting out cereal fibre and missing out on probiotics from yoghurt compromise your intestinal balance? And what about constipation?

Can you keto adapt?

There’s also talk of the ‘keto flu’ that you need to get through as you adapt to a ketogenic diet. Advocates of keto diets for endurance say adaptation may take months, but that the performance gains are worth it.

The traditional diet for athletes has been a relatively high-carbohydrate intake to maintain muscle glycogen stores for high-intensity exercise. So, does a ketogenic diet work for strength training as well as it has been claimed it does for cardio?

Casual ketosis

One approach is to dip in and out of ketosis. But what happens if you eat more carbohydrate on a single day and come out of ketosis? Can you get back into keto the next day, or have you blown it?

It’s a bit technical

Unlike the popularity of arguably less extreme low-carbohydrate diets for fat loss, like the Atkins Diet (with around 50 grams per day of total carbohydrate), a ketogenic diet appears to be more restrictive, prescriptive and technical. Even a Paleo diet, for all its rules, is more liberal, allowing carbohydrate from sweet potatoes, yams, blueberries and other specific foods.

With rising rates of obesity and diabetes, some are saying we need to be more extreme in our dietary approaches and consider ketogenic diets to improve metabolic health and reduce risk of diet-related disease. But others say the nation simply eats too much junk food and curbing intake of sugar, processed fats and alcohol is all that is needed.

The debate is sure to rage on, and your clients may well ask you about keto, so it’s worth your while exploring the pros, cons and practical know-how behind this dietary approach – and indeed any of the latest diet trends.

Get to really know keto
Keep yourself and your clients in the know about keto by attending the online event, Ketogenic Diets – #FadOrFuture? on 10 August with expert speakers, including FILEX regular Matt O’Neill and Institute of Sport Head of Nutrition, Professor Louise Burke.

Use Coupon Code – AFNFOF – to save $10 on your registration for the live and recorded webinar package at

Matt O’Neill, Dietitian BSpSc, MSc(Nut&Diet), APD, AN is director of the SmartShape Centre for Weight Management and creator of the Metabolic Jumpstart nutrition system.

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