The high-fat, low-carb ketogenic diet still remains one of the most popular around the world, but experts have warned it should be practised with caution.
Essentially, the keto diet is a way to cut back on carbohydrates (usually 50 grams a day or less) to help the body achieve a state of ketosis. Without the carbs, the body has to burn fat (rather than sugar) for energy.
According to Robbie Clark, an Australian accredited practising dietitian and sports nutritionist, restricting certain foods and/or food groups can lead to nutrient deficiencies and increase the risk of other health issues.
"Nutrition professionals advocate for a 'balanced' diet without the restriction of foods unless it's clinically necessary to improve the health of their clients," Mr Clark told news.com.au
"The keto diet is considered to be a restrictive diet particularly around whole grains, legumes, starchy vegetables and fruit."
KETO DIET: 'WORST FOR HEALTHY EATING'
Mr Clark's comments come after the diet was rated the worst for healthy eating in 2020 out of 35 others in the annual diet roundup by US News & World Report.
It also received poor rankings in nearly every category of the study that included input from nutritionists and specialists in diabetes, heart health, human behaviour and weight loss.
"I'm not surprised this diet ranked poorly for a couple of reasons – any form of restrictive diet is not beneficial for 'healthy eating behaviours' or the psychology of eating long-term.
"Hence why it's considered a fad diet."
The rankings were based on seven categories, with each diet rated on a scale from one to five. It included nutritional completeness, how easy the diet is to follow, the potential for long and short-term weight loss and the safety and possible side effects.
The Mediterranean diet and WW (formerly Weight Watchers) came out on top as the best overall diet and best weight-loss diet respectively.
Keto scored poorly on the list of heart-healthy diets and also ranked low for sustainability as it requires strict limitations on consuming any kind of carbohydrates.
The only category it excelled in was fast weight loss where it ranked third with Atkins, Weight Watchers and Jenny Craig.
WHY IS KETO SO POPULAR
The keto diet has, in recent years, become a widely recognised protocol with a high-fat, low-carbohydrate regimen.
However, Mr Clark said it was initially developed as a therapeutic tool for patients with refractory epilepsy and has since been used as a complementary treatment in a multitude of conditions, including cancer, depression, anxiety, epilepsy, obesity, Parkinson's disease and Alzheimer's.
"The keto diet in Australia is highly popular mainly for its benefits in fast-tracking fat loss and improving insulin and blood glucose response. People forget that this diet has been clinically proven to help manage and treat other chronic health conditions as mentioned above," Mr Clark said.
The keto diet ranked poorly in the annual report due to the difficulty of following it long term and because it cuts out healthy food groups like whole grains and fruits that are high in carbs.
"Australian adults should be aiming for 25-30g of fibre each day. This may be challenging for people following an unsupervised keto diet as most keto diet guidelines recommend you stay between 15 to 30g of net carbs per day or 5 to 10 per cent of total calories," Mr Clark told news.com.au
"This is not to say it's unachievable, just more challenging, especially since the most restrictive foods on a keto diet are our largest and best sources of fibre."
PROS AND CONS OF A KETO DIET
According to Mr Clark, who is also the co-founder of HealthBank, and other nutritionists, several key physiological benefits occur when your body remains in a state of ketosis.
"As a result, there are several key adaptations and improvements of metabolic functions in the body, including improved memory and learning, antioxidant action, appetite reduction and
lipolysis stimulation (break down of fat)," Mr Clark said.
James Kuhn, an accredited Australian nutritionist and body science expert, said a well-constructed keto diet was rich in minimally processed foods.
"Like all well-constructed diets, it's built on a foundation of nutrient dense whole foods such as nuts, seeds, fibrous vegetables, proteins and healthy fats," he told news.com.au
But he said perhaps one of the biggest benefits was that ketones and ketogenic diets helped manage hunger.
"A systematic review by researchers from the The Boden Institute of Obesity in Sydney found individuals were less hungry and exhibited greater fullness/satiety while adhering to ketogenic diets and had a reduced desire to eat," Mr Kuhn said.
However, like any diet protocol there are also some cons, from mild side effects to safety concerns, Mr Clark explains.
"One side effect of ketosis is the 'keto flu'. The first two weeks of transitioning to a keto diet are often the most challenging. Several symptoms, known collectively as the 'keto flu', can result as the body adapts to a reduced intake of carbohydrates," he said.
"These transition symptoms usually begin within two to seven days of starting the diet, lasting several days to a few weeks and can include: nausea, headaches, fatigue, dizziness/light-headedness, insomnia, reduced exercise tolerance and constipation."
Even though the keto diet has promising therapeutic potential in many health conditions, there are certain subgroups where caution needs to be exercised.
Mr Clark said those are pregnant or breastfeeding women, those who have adrenal and thyroid conditions and a gallbladder and fat metabolism disorder.
"The diet may elevate cortisol and negatively impact patients with existing hypothalamic pituitary adrenal (HPA) axis dysregulation and even high intensity athletes," he explained.
"Research has shown that very low carb diets can lower thyroid hormone levels, specifically T3, the most metabolically active form of thyroid hormone in the body."
Mr Clark said there was no "magic pill", nor a quick fix, for weight loss, adding that changing eating habits should occur gradually, especially if you have existing poor eating behaviours.
WHAT DOES A SUCCESSFUL WEIGHT-LOSS PROGRAM LOOKS LIKE
A successful weight-loss program looks at many aspects including nutrition, exercise, hormone balance, stress management and proper sleep hygiene, according to Mr Clark.
He said it also required support and a complete lifestyle change.
"The sad truth is that fad diets will not change the relationship people have with food," he told news.com.au
He said those struggling with their weight or health who have tried many different approaches with little success may benefit from the advice of a nutrition professional, accredited practising dietitian or GP.