Hot topic: Ketogenic diet
Variations of the low carbohydrate diet have dipped in and out of popularity over the years. According to Google Trends, the ultra-low-carb ketogenic diet hit peak popularity in January, suggesting it will be all the rage in 2018. But what is the ketogenic diet, and is it worth buying into the hype? Read on for a summary of the evidence.
What is it?
A ketogenic diet is very low in carbohydrates, and its aim is to achieve and maintain a state of ‘ketosis,’ which means the body switches from burning carbohydrates, to burning fat for energy.
So this means eating very few carbohydrate-rich foods, such as grains, legumes, fruit, dairy foods and starchy vegetables like corn and potato, whilst also limiting discretionary foods like chips, soft drink, ice cream, cakes and biscuits.
But where a ketogenic diet differs from other ‘low-carb’ diets, is in its long-term and severe carbohydrate restriction. To maintain ketosis, just 50g of carbohydrate or less is allowed per day. Considering a medium banana contains around 20g of carbohydrate, you can see just how few carbs are allowed when following a true ketogenic diet.
What are carbohydrates and why do we need them? Find out more by watching our video here.
So what can I eat?
With the focus off carbohydrate foods, a ketogenic diet is relatively high in protein (eating more foods like meat, chicken, fish, eggs, cheese or tofu) and high in fat, with olive oil, nuts and seeds, coconut oil and high-fat dairy foods like cheese and butter being recommended.
Low starch fruit and vegetables are also allowed, such as leafy greens, mushrooms, cabbage, avocado, berries and citrus fruits.
Breakfast: two eggs fried in olive oil, sautéed spinach and tomato
Morning tea: handful of nuts
Lunch: Chicken stir-fry with cauliflower rice
Afternoon tea: cup of strawberries
Dinner: Steak with greens cooked in olive oil
Why do it?
Initially, the ketogenic diet was developed in the 1920’s as a medical treatment for epilepsy (more on this below), but in popular culture it’s now filtering through as a celebrity-endorsed health and wellness lifestyle choice.
Advocates of the diet point to weight loss and maintenance, appetite suppression, and mental clarity as just some of the benefits of following a ketogenic diet.
Following the ketogenic diet means significantly upping intake of protein and fat.
What does the evidence say?
There is promising research that supports a ketogenic diet as a medical treatment for some cases of epilepsy in children.[i] While it’s not understood exactly how it works, trials have shown that in children unresponsive to medication, a ketogenic diet can help to reduce seizures. However, most research is limited to small studies just in children, so can’t be applied to the whole population.
When it comes to weight loss, some studies among overweight and obese adults show that very low carbohydrate diets may be more effective than regular energy-restricted diets in the short-term (up to six months). But in the long-term (up to five years), there’s little to no difference between the two approaches. And when looking at risk factors for cardiovascular disease, some studies found both benefits and drawbacks to the ketogenic diet; while some studies reported greater weight loss and improvements in HDL (or healthy cholesterol) followers either had less of an improvement in total and LDL (or unhealthy cholesterol) or an increase in LDL cholesterol, compared with low fat diets. Similar to the research in epilepsy, in longer-term weight loss studies, researchers noted that followers found it difficult to stick to and also found that most carbohydrate intakes were often not low enough for ketosis to kick in at between 36-100g per day. So it’s hard to draw conclusions about the ketogenic diet’s suitability for weight loss and long-term health, compared with a regular low carbohydrate diet.[ii]
A true ketogenic diet is hard to follow due to the minimal amount of carbohydrates allowed – just 50g a day.
Why shouldn’t I do it?
While the idea of burning fat sounds like an efficient way of losing weight, it’s a difficult diet to follow long term. The high drop-out rates and poor compliance in studies are partly why research is lacking around the ketogenic diet – as it’s highly restrictive, it is hard to maintain.
Being in ketosis means our body releases chemicals called ketones, which are detectable in the breath, urine, and blood. This signals the change in fuel being used by the body and can result in noticeable and unpleasant side effects.
And due to its high fat content – up to 90%, many consider the diet unpalatable and inconvenient for social situations, and it can cause side effects like constipation, abdominal cramps, diarrhoea and vomiting.
By eliminating most carbohydrate-rich foods, maintaining ketosis means missing out on a range of healthy foods, like fruit, vegetables, grains and legumes. Being rich in fibre, vitamins, minerals and phytochemicals, these foods can help protect against chronic diseases like cardiovascular disease, type 2 diabetes, and colorectal cancer.[iii][iv] These foods also keep us feeling satisfied between meals, and help to keep our digestive systems healthy, as the good bacteria in our gut feeds on resistant starch found in many carbohydrate-rich foods. Without this, our gut may not function at its best and the evidence for maintaining diverse microbiota and the role of gut health in our overall health continues to grow.
Side effects like constipation, cramping and vomiting are not uncommon when following the ketogenic diet.
So what’s the bottom line?
Ketogenic diets are peaking in popularity this year, but without strong evidence to support them you needn’t feel pressured to cut out carbohydrate foods, without medical advice to do so. In fact, by eating fruit, vegetables, grains and legumes as part of a balanced diet, you’re fuelling your body with healthy foods to protect your health in both the short and long-term.
For personalised nutrition advice, we recommend seeking support from an Accredited Practising Dietitian (APD). APDs are nutrition scientists that tailor their advice to you, based on the most up-to-date evidence. Find an APD near you by heading to daa.asn.au and ‘Find an APD.’
Always seek advice from an Accredited Practising Dietitian when considering a diet change.
[i]Martin K, Jackson CF, Levy RG, Cooper PN (2015). The Cochrane Collaboration. Accessed from: http://www.cochrane.org/CD001903/EPILEPSY_ketogenic-and-other-dietary-treatments-epilepsy
[ii] PEN: Practice-based Evidence in Nutrition (2018). Healthy weight/obesity – dietary approaches. Accessed from: http://www.pennutrition.com/KnowledgePathway.aspx?kpid=15329&pqcatid=145&pqid=25889
[iii] World Cancer Research Fund International/American Institute for Cancer Research. (2017). “Continuous Update Project Report: Diet, Nutrition, Physical Activity and Colorectal Cancer.” Available at: wcrf.org/colorectal-cancer-2017.
[iv] Aune D, Keum N, Giovannucci E, Fadnes LT, Boffetta P, Greenwood DC, et al. Whole grain consumption and risk of cardiovascular disease, cancer, and all cause and cause specific mortality: systematic review and dose-response meta-analysis of prospective studies. Bmj. 2016;353.