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Low Carb High Fat Diet

The low carb high fat (LCHF) diet has been around since the turn of the 21st century and as its name suggests is a relatively simply diet in theory, but since 2010 it has come to prominence.This is due in large part to its endorsement by a number of high profile scientists and emerging supporting scientific evidence. Tim Noakes, a South African professor of exercise and sports science at the University of Cape Town is arguably the most well known and respected advocate of the LCHF diet. At the time of writing, a book he has co-authored entitled, ‘The Real Meal Revolution’ is the current bestseller in South Africa. Another noted proponent is Dr Peter Bruckner, who at time of writing is the current doctor for the Australian Cricket Team, who just reclaimed the 2013/2014 Ashes Series. But before listing all the proponents and advocates of the LCHF diet, it’s important to provide a summary of its essential features, characteristics and underlining theory. To conclude, the article will touch on some athletes and sports that are using the LCHF diet with success.

What is the Low Carb High Fat Diet?

The LCHF diet centres on the consumption of a very low amount of carbohydrate (5-10%) as a percentage of total daily calorie intake. It is coupled with medium consumption of protein and high intake of fat. As such, on a broad level, a typical LCHF diet has the following macronutrient composition:

  • Fat (70-80% total calorie intake)
  • Carbohydrate (5-10% total calorie intake)
  • Protein (10-20% total calorie intake)

With this macronutrient composition, the LCHF diet consists predominantly of the following foods:

  • Meat/Poultry/Fish
  • Dairy/Cheese/Eggs
  • Oils/Nuts/Butter/Duck fat/Lard
  • Non-Starchy Vegetables/Salads

While not overly strict in terms of foods one cannot eat; there are essentially two important types of foods/nutrients that a LCHF diet avoids. These include:

  • All grains (i.e. pasta, bread, rice)
  • All types of sugars (fructose, agave, malt, syrups)

Carbohydrate Content of LCHF Diet

The most important aspect of the LCHF diet is the carbohydrate content. While there is some variability in opinions, the general consensus is that most individuals need to consume between 50 -100g of carbohydrate a day for the diet to be effective. The amount of daily carbohydrate one can tolerate can vary, with some individuals needing to eat less than 50g per day, while others (such as endurance athletes) can sometimes tolerate up to 150g per day. In any case, a low daily carbohydrate intake forms the cornerstone of the LCHF diet and if individuals experience less than optimal results, the general advice is to reduce carbohydrate intake even further13.

Keto-Adaptation and the LCHF Diet

The other key feature of the LCHF diet is implementation. This involves a process popularly termed ‘keto-adaptation’, whereby the body’s metabolism gradually changes into a state popularly termed ‘nutritional ketosis’. Keto-adaptation is the term given to the process of time whereby the body adjusts its metabolism to derive a much higher (than normal) percentage of its energy needs from ketones. Ketones are a  break down product of fat and levels rise whenever the body significantly increases its burning of fat. During keto-adaptation, an individual switches from eating a moderate/high carbohydrate diet to a low carbohydrate diet with a compensatory increase in fat consumption. This process typically takes between 2-3 weeks, but can be shorter or longer depending on the individual and their body's metabolic adaptation13. Once this keto-adaptation has taken place, the body is said to be in a state of ‘nutritional ketosis’ or ‘fat-adapted’. This state is distinct from the medical condition of ketoacidosis that accompanies uncontrolled diabetes. Plasma ketone levels during ketoacidosis are typically upward of 15nM, whereas nutritional ketosis is defined by plasma ketone levels in the range of 0.5-5nM; a level which is said to be safe and manageable for the human body.

Science of LCHF Diet

The research into the comparative effects of low carbohydrate diets versus low fat diets for weight loss has been ongoing for decades, with a number of pioneering studies being conducted in the 60’s & 70’s1-3. However, there has been a noticeable acceleration in the number of studies published since the turn of the century4-9. As such there is a considerable body of evidence now showing that weight loss is more effective when using a low carbohydrate diet versus a low fat diet with the same calorie content. In particularly, low carbohydrate diets have been shown to be effective in treating type 2 diabetes, with significant reductions in fasting insulin and blood glucose some of the most common findings. Popular LCHF advocate, Professor Timothy Noakes recently authored a publication in the South African Medical Journal which detailed the communications from 127 individuals self-reporting their weight change following adoption of a LCHF diet16. In this study, the total combined self-reported weight loss was 1900 kg (range 5 kg gain to 84 kg loss). Sixteen subjects reported the LCHF diet ‘cured’ (i.e. medications no longer required) one or more of their medical conditions, most commonly type 2 diabetes mellitus (T2DM), hypertension and hypercholesterolaemia. Another 9 subjects with either type 1 diabetes mellitus or T2DM reduced medications as did 7 patients with hypertension; 8 no longer suffered from irritable bowel syndrome16. As an aside, low carbohydrate/ketogenic diets have also been used successfully for several decades in the treatment of epilepsy11.

Theory & History of LCHF Diet

Beliefs and theories regarding the traditional diet of our ancestors form an important part of the LCHF diet philosophy. Many lines of evidence suggest that our human ancestors evolved as hunter-gatherers whose ability to migrate into barren or temperate regions depended upon their ability to survive prolonged periods of fasting and to adapt to hunting and gathering of less carbohydrate-rich food13. It is believed that the adaptation to this low carbohydrate diet allowed our human ancestors to become highly specialised hunters and herders that lived as mobile cultures in concert with the movement of animals that fed them. Some recent examples of these low carbohydrate nomadic cultures include the Masai herdsmen in Central Africa, the Bison People of the North American Great Plains, and the Inuit in the Artic13.

Traditional Aboriginal Diet Thought to be Low Carb High Fat

Our own Australian Aborigines are one of the last indigenous cultures around the world to have their diet changed dramatically by the agricultural revolution and permanent European colonisation two centuries ago10. Australian Aborigines were preagriculturalist hunter-gatherers who had adapted extraordinarily well to life in a variety of habitats15. As has been widely publicised, colonization had serious negative effects on the health and well-being of Aborigines, who now are the unhealthiest subgroup in Australian society10. The change from active and lean hunter-gatherers to a more sedentary group of people whose diet is now predominantly Westernised has had particularly negative effects on the incidence of cardiovascular disease and type 2 diabetes mellitus, the very diseases which a LCHF diet is said to be most beneficial for.

Composition of Traditional Aboriginal Diet

Research on the traditional diet of Aborigines prior to colonisation suggests the diet was predominated by hunted animal foods including mammals, birds and fish, with the eggs of many of these creatures also an important component10. Local fruits (wild plums, figs, etc), nuts (macadamia, chestnuts, walnuts, almonds) seeds (mulga, acacia) and vegetables (carrots, onions, bush potatoes) also formed a minor part of their diet10. So there are reasonable grounds to suggest that the traditional diet of native aboriginals contained moderate (if not high) amounts of fat, moderate protein, together with low amounts of carbohydrate. Moreover, historical studies of Aboriginal diets highlight certain dietary practices that favoured the consumption of fat. For instance, witchetty grubs (a widely known component of the Aboriginal diet) are high in fat and have a composition similar to that of olive oil. Moreover, the fatty parts of animals such as goannas were traditionally very popular with Aborigines after being cooked whole on red hot coals10.

Australian Aborigines are just one of the indigenous peoples across the globe thought to have had historically low carbohydrate intakes - who now exhibit extremely high prevalence rates of obesity and type-2 diabetes. Some other examples include the Gulf States in the Middle East, Pacific Islanders, and First Nations in Canada13. The experience of these cultures is often cited as supporting evidence for the LCHF diet.

Professor Grant Schofield from the Auckland University of Technology has also conducted research on the food habits of several Pacific countries including Tonga, Tokelau, Kiribati and Vanuatu. His findings also suggest that the traditional diet of these people is high in fat and low carbohydrate, and when changed to a more western/urbanised diet higher in sugar and carbohydrate, common health issues such as type 2 diabetes and obesity start to develop.

Carbohydrate Intolerance

Proponents of the LCHF diet assert that from an evolutionary perspective, a high carbohydrate diet can represent a significant metabolic challenge that some find difficult to meet as early as their adolescence years (hence the dramatic increases in childhood obesity) and into the middle years of life. These same individuals also typically respond poorly to traditional interventions such as vigorous exercise, high intakes of micronutrients and/or fiber from fruit and vegetables, avoidance of simple sugars and energy restriction. These widely perceived ‘healthy lifestyle’ measures appear insufficient to fully counteract the negative effects of a substantial contribution of carbohydrate to daily energy intake.

Obesity and type 2 diabetes are underpinned by insulin resistance and the LCHF diet advocates suggest that individuals prone to these conditions and unresponsive to normal intervention measures deserve to be identified as “carbohydrate intolerant”. As with other single nutrient intolerances (e.g., lactose, gluten, fructose), the preferred intervention is to reduce one’s dietary intake below the threshold level that produces symptoms. For carbohydrate intolerant individuals, this tends to be somewhere in the vicinity of 50-100g per day13.

The concept and notion of carbohydrate intolerance is gaining increasing recognition and is generally understood to be a manifestation of insulin resistance. It is associated with high blood triglyceride, high blood pressure, and in its most severe form, type-2 diabetes. Carbohydrate intolerant individuals are reported to show dramatic clinical improvement when dietary carbohydrates are reduced13 as per the LCHF diet.

LCHF Diet and Exercise Performance

Opponents of the LCHF diet argue that there are very few studies, particularly in the context of exercise performance, which prove that the LCHF diet is both sustainable and beneficial for performance. However, this argument is countered by the fact that most studies don’t allow for a long enough keto-adaptation phase of between 2-4 weeks, as advocated by the LCHF diet. A number of studies with elite athletes have been conducted where fat intake was significantly increased and carbohydrate decreased, but with mixed results17. Proponents of LCHF diet argue that the variable results relate to the lack of consistency in the period used for fat-adaptation, with the time ranging from one day to two weeks. However, there is a trend for improved performance when the 'fat-adaptation' period was 2 weeks or more18.

Dr Stephen Phinney and Dr Jeff Volek are two US-based collaborative researchers who are active proponents of the LCHF diet. Phinney is credited with being the first researcher to publish one of the only studies in competitive endurance athletes showing a LCHF diet is equally beneficial for performance as a normal high carbohydrate ‘balanced’ diet in a group of highly trained cyclists12. Like Phinney and Volek advocate in their popular co-authored book titled “The Art & Science of Low Carbohydrate Performance”13, cyclists in the study where subject to a LCHF diet for 4 weeks so as to allow sufficient time for keto-adaptation. Compared with a normal high carbohydrate diet, after 4 weeks on a LCHF diet, on average, cyclists' maximal fat burning rates were over three times higher13 and what’s more the cyclists did not experience any decrease in performance.

Anecdotally, there are increasing reports of sportsmen and women adopting a LCHF diet with resultant beneficial effects on performance. While a discussion of the mechanisms explaining the reported benefits are outside the scope of this article, some commonly reported benefits include better recovery and sleep together with a dramatically reduced reliance on the intake of carbohydrate during exercise. Some examples of high profile athletes and advocates include Timothy Olson (2012 & 2013 winner of western states 100), David Zabriskie (professional cyclist) and Simon Whitfield (Olympic triathlete).


The LCHF diet certainly stands as one of the more scientifically valid diets that also makes a lot of sense from an evolutionary point of view. Other major benefits include its general tendency to reduce hunger cravings, its efficacy for weight loss and blood sugar/insulin control and its non-reliance on strict calorie-counting. Because the LCHF diet only really enforces the restriction of grains, it still allows for a great variety of food selection. However, endorsement of the diet by government agencies and large food corporations may prove difficult, simply because of the size of the wheat/sugar industry and its lobbying power.

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