Brett Melanson - PhD Candidate in Behavioural Neuroscience.
Carbohydrates have frequently been referred to as an essential source of energy and a common staple in many diets. This is because of their efficient sugar-molecule backbone that is utilised by a variety of cells in the body for energy and their ability to access the brain.
Our bodies have specialised machinery within the cell that can break these sugar molecules down into fundamental components, such as glucose and pyruvate. These fundamental building blocks of carbohydrates are then burned through a series of intracellular cascades to generate adenosine triphosphate (ATP) - the primary source of energy for the majority of cells (Dunn & Grider, 2020). This suggests a heightened dependency on carbohydrates by our bodies to generate energy which allows us to carry out our day-to-day tasks.
Moreover, carbohydrates are typically referred to as ‘fuel for the brain’ as a variety of studies have shown that glucose is efficiently utilised by neurons to fuel action potentials and synaptic transmission between cells in the central and peripheral nervous systems (Dienel, 2019).
These studies, in addition to the physical and psychological effects that can occur when we experience low glucose in the blood (i.e., feeling hangry; Horman et al. 2018) have led us to believe that our body and brain must be dependent on glucose. It is important to note, however, that these effects are typically experienced at dangerously low levels of glucose in the blood which mainly occur in states of disease (e.g., hypoglycemia) or extreme starvation.
Conversely, during brief periods of food restriction, such as in the case of intermittent fasting, the body is well-equipped to maintain normal blood glucose levels as long as other energy resources (fatty acids, amino acids, etc.) are present in the diet/body (e.g., fat stores), since components from these compounds can be used to synthesise glucose (Paoli, 2014). So, a feeling of starvation can have significantly different consequences on the body compared to simply feeling “hungry” during a planned episode of fasting. This will be addressed in detail with evidence supporting the body’s ability to use fat as energy in the absence of glucose.
In the last 20-30 years, there has been a significant increase in diet-related disorders and disease, such as diabetes mellitus, metabolic syndrome, and obesity (World Health Organisation, 2016). In Australia alone, rates of overweight cases and/or obesity have increased in the total population by roughly 15% in the last 15 years, and about 25% of these cases were observed in individuals under the age of 18. Pre-diabetes describes a condition in which blood glucose levels are higher than normal, although not high enough to be diagnosed with type 2 diabetes. Two million Australians have pre-diabetes, a condition which has no signs or symptoms, but puts you at higher risk of developing common lifestyle diseases.
Overconsumption of carbohydrates causes the body to store excess sugar in the form of fat (i.e., lipids), for use at a later time, which never comes to pass. (Mohan et al. 2018)
From an evolutionary standpoint, this is advantageous, as it serves to provide energy for the body during periods of low energy resource availability, such as hibernation during the winter. Unfortunately, us humans are not ones to typically hibernate during the winter, but instead are becoming more frequently known for snacking out on the couch or eating a high-carb meal only to return to our desks for the remainder of the day.
This is a key scenario where high supply/low demand of carbohydrates can lead to weight gain, as the ingested sugar will readily convert to fat if it is not being used up. And, since we tend to incorporate carbohydrates in each of our meals throughout the day, this fat is never given the opportunity to break down and fuel the body with energy.
But what if we can tap into these fat stores to generate energy in the absence of glucose, and directly impede this “sugar-to-fat” process altogether?
Alluding to this, there are studies that have revealed the incredible power of ketogenesis - a gradual, physiological process that facilitates the body’s ability to tap into fat stores during extended periods of low glucose availability to produce energy (Paoli, 2014).
Although this process is primarily responsible for preserving the body’s functions during periods of starvation, many individuals have utilised this knowledge to “hack” into these fat stores simply by changing the way they eat.
Ketogenesis achieved through food and fasting gradually shifts the body to begin relying on fats rather than glucose. One may gradually become fat-adapted and shift the body into a state of ketosis - the breakdown of fatty acids into ketones (Murray et al. 2016). This requires consuming a high fat, low carb (less than 20 g per day; Paoli, 2014) diet over an extended period of time. Keto-adaptation can take 2-3 weeks and the novelty can be stressful if it's not managed properly.
Ultimately, it's a lifestyle change. Use of keto supplements like MCT oil, Esters, Electrolytes and fibre can help with the transition. Continued use can be of benefit for maintenance, or for tactical benefits such as sports performance.
When the body begins to shift its energy resources to utilise fat stores, lipids are broken down into fatty acids, which are subsequently broken down into the energy-efficient lipid metabolites: ketone bodies. Two primary examples of these are acetoacetate and beta-hydroxybutyrate (Koutnik et al. 2019).
Importantly, the body is able to maintain normal glucose levels in the blood, avoiding hypoglycemia, partly by breaking down backbones of fatty acids and converting them into glycerol—this occurs gradually as the body shifts its dependence on ketone bodies for energy (Paoli, 2014). Thus, with a ketogenic diet, one is able to hack into body fat stores, use these stores for energy, and maintain normal glycemic control at the same time.
Learn more about how the keto diet can help mitigate an obesity epidemic.
There is now evidence indicating that ketones actually produce more energy per mole of substrate than glucose. Specifically, the end-product of glycolysis (i.e., cellular process that breaks down glucose) known as pyruvate produces 10 ATP, whereas combustion of a ketone body like beta-hydroxybutyrate produces 13 ATP (Murray et al. 2016). Of course, glucose has been deemed the primary source of energy in the brain, but this is likely due to the inability of fatty acids to cross the blood-brain barrier (Paoli, 2014).
Since ketones are highly efficient energy molecules, and there is evidence that burning ketones instead of glucose preserves carbohydrate stores in muscle (Murray et al., 2016), it would make sense that transitioning the body’s energy dependence from glucose to ketones would prove to be beneficial in the long run, both mentally, and physically.
Image source: https://faseb.onlinelibrary.wiley.com/doi/full/10.1096/fj.201600773R
So, is there evidence to support the idea that ketones are more efficient molecules in tasks of cognitive and physical performance? Let’s dive right into the science to find out.
It is no doubt that carbohydrates have been a popular food item for centuries, but the more we begin to understand ketone bodies and their energy-efficient nature, it seems as though we are accessing an additional dimension of performance enhancing strategies that received little attention in the past.
The use of ketone-generating diets, whether it be intermittent fasting, ketogenic, orlow-calorie meal planning, have become popularised around the world as we begin to understand the advantages ketone bodies have over carbohydrates.
Furthermore, we’re seeing the habitual consumption of the typical quantity of carbohydrates is excessive (not discounting the value of fibre) when compared to the average level of activity. Intake far exceeds energy requirements. The more we know, the better; and, better it seems as if science continues to develop an understanding for the long-term effects of ketogenesis on the body and mind.
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