Ketogenic diet and weight loss
The ketogenic diet was first introduced in 1920 as a treatment for children with epilepsy (Wheless, 2008). As more research was done on the effectiveness of the ketogenic diet, it was reported that the traditional ketogenic diet consisted 1 gram of protein per kilogram body weight, a restricted carbohydrate intake of 10–15 g and the remaining calories in fat per day and the purpose remained primarily as a treatment for epilepsy (Wheless, 2008). When carbohydrate is restricted, the body can go into a state of ketosis, where blood ketone concentrations increase to ~3-4 mmol/L, compared to <0.3 mmol/L with a regular diet (Paoli, Rubini, Volek, & Grimaldi, 2013). In recent years, predominately after the discovery of insulin, the carbohydrate-restricted diet started gaining popularity as a treatment for diabetes (Feinman et al., 2015). In his review on carbohydrate restriction for the management of diabetes, Feinman et al. (2015) defined a very low-carbohydrate ketogenic diet and a low-carbohydrate diet slightly differently. He defined a ketogenic diet as very low-carbohydrate, at either 20–50 g of carbohydrates per day or less than 10% of a 2000 kcal per day diet. He also made a note that while his definition was derived based on the carbohydrate levels required for the body to reach a state of ketosis, because of the variability between individuals, ketosis still might not occur. He defined a low-carbohydrate diet as less than 130 g of carbohydrate per day or less than 26% of total energy.
Using those similar definitions, a review done by Noakes and Windt (2017) summarised the effects of both a very low carbohydrate high fat (ketogenic) diet, and low-carbohydrate high fat (LCHF) on various parameters. In terms of weight loss, the evidence gathered for this review demonstrates that both a ketogenic and LCHF diet can lead to greater or if not equal weight loss compared to the other diets that were used in all studies they reviewed. All the diets that were tested were effective in short-term weight loss but most of the time would be followed by some regain of weight as adherence to the diet was reduced. Their hypothesis was that the weight loss from a LCHF diet could be a result of the advantageous adaptations in the body’s metabolic function such as an increase in the thermic effect of protein, an increased turnover of protein for gluconeogenesis and energy loss through the passing out of ketones in sweat or urine. There have been suggestions that the weight loss from a ketogenic diet is due to the loss of water (Yang & Van Itallie, 1976). However, a study which measured body composition using dual-energy X-ray absorptiometry (DEXA) indicates that the weight loss from a carbohydrate-restricted diet is a reduction in fat mass (Volek et al., 2009).
Energy Balance and diet
According to the principle of energy balance, a change in body weight will occur when energy intake is not equals to energy expenditure over a period of time (Hill, Wyatt & Peters, 2003). When energy expenditure is greater than energy intake, this is described as a state of negative energy balance that will usually result in a loss of body mass, which translates to weight loss. A diet that follows the principle of energy balance is essentially looking at achieving negative balance by reducing energy intake. Using mathematical modelling, Hall et al. (2011) presented that even though the way an individual’s body weight responses to changes in energy intake is highly variable, which can lead to different changes in weight, loss in body fat was still reported in all diets that reduced energy intake in the short run. The effectiveness of exercise on weight loss is also not entirely dependent on the exercise, but on the individual’s variability on substrate utilization as well (Barwell, Malkova, Leggate, & Gill, 2009). While reducing energy intake has shown to result in weight loss, the broad interpretation of a diet that follows energy balance may be less straightforward and fairly complicated when attempting to adopt a diet based on the principles of energy balance for weight loss on your own.
A Ketogenic diet can follow the principles of Energy Balance
A ketogenic diet can be described as a protocol-based diet where macronutrients are pre-determined. A diet that follows the principles of energy balance approach to weight loss is to achieve non-equilibrium, which does not necessarily provide a guideline on the breakdown of macronutrient intake. Due to individual variability in baseline body composition, energy expenditure and substrate utilization, one would need to have some familiarity and/or be in-tune with their own physiological parameters in order to decide the macronutrient breakdown on their own. Even though the principle of the ketogenic diet has been widely explained as a very-low carbohydrate, high fat diet approach, it does not indicate that it does not follow the principle of energy balance. A ketogenic diet can therefore also be a diet that follows the principle of energy balance. It is interesting to note that the study by Johnstone, Horgan, Murison, Bremner, and Lobley (2008) which compared a high-protein, low carbohydrate diet to a high-protein, medium carbohydrate diet, referred to weight loss in both diets as an indicator of negative energy balance. The study by Partsalaki, Karvela, and Spiliotis (2012) looked at the effects of a carbohydrate-restricted diet compared to a calorie-restricted diet because the traditional recommendation for the management of obesity, which is a calorie-restricted diet, seemed to be theoretically based on maintaining negative energy balance. They reported weight loss in both diets, greater for ketogenic diet, even though there was no calorie intake restriction in their ketogenic diet protocol. Evidences cited in the review by Noakes and Windt (2017) also highlighted that a low-carbohydrate, high fat diet is able to control energy balance as well as encourage the intake of high nutrient density foods. With guidelines on the composition of carbohydrate and fat in a ketogenic diet, along with instances of reported weight loss of >10% (Mark et al., 2016), it seems to be the easier and effective approach to adopt. While it might seem straightforward to implement a ketogenic diet, it still might not be suitable for everyone due to individual variability. Nutrition strategies to be fundamentally based on managing energy balance and ensuring high nutrient density is still recommended (Noakes & Windt, 2017).
One way of quantifying physique is with body mass measurements, a full anthropometric profile and somatotyping (Slater et al., 2005). Of the three somatotypes, mesomorphy, which is used to describe muscloskeletal robustness and ectomoprhy, which is used to describe linearity or slenderness (Carter, Carter, & Heath, 1990), both could be classified as a lean physique. Choosing a diet to achieve a lean physique can either be to support the goal of reduction of fat mass or increase fat-free muscle mass.
As both a ketogenic diet and a diet which follows the principle of energy balance can be as effective in weight loss and helping to achieving a lean physique, diet adherence could therefore be a factor in determining their effectiveness in maintaining a lean physique. It has been shown that there is no increased risk of cardiovascular disease with a carbohydrate-restricted, high fat diet in the short term of 12 weeks (Volek et al., 2009) as well as no adverse metabolic effects on the body nor an increase risk of cardiovascular disease from long term (>1 year) adherence to a low-carbohydrate, high-fat diet (Grieb et al., 2008). Multiple studies cited by Noakes and Windt (2017) also found that there is no evidence or epidemiological data to support the theory that intake of saturated fat is the cause of coronary artery disease. With that in mind, both the ketogenic diet and a diet which applies the principle of energy balance would be safe to sustain long term when adopted safely and appropriately. In terms of attrition rate, three studies cited in the review by Noakes and Windt (2017) reported that adherence to low-carbohydrate, high-fat diets were the same as low-fat, high-carbohydrate diets. A systematic review conducted by Hession, Rolland, Kulkarni, Wise, and Broom (2009) highlight a higher attrition rate of low-fat, high carbohydrate diets compared to low-carbohydrate, high diets, across 13 studies with a total of 1222 participants. A ketogenic diet with low carbohydrate intake has also been shown to be able to reduce perceived hunger, leading to a reduced intake of food (Alexandra, Graham, Sandra, David, & Gerald, 2008). Choosing the diet to help sustain a lean physique could then be down to the individual’s motivation to achieve the goal and their adherence to the diet they have chosen.
When quantifying physique by somatyping, it would be interesting to note that the study done by Silventoinen et al. (2020) found that genetics plays a role on the relationship between children’s somatotype and their physical fitness. It might therefore be worth taking into account an individual’s genetic background and inherited physique when deciding, and evaluating the effectiveness of any diet intervention on achieving and sustaining a targeted physique
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