Shaun Ward MSc ANutr
What Is The Ketogenic Diet?
The ketogenic diet, also known as ‘keto’ or ‘ketosis diet’ is a popularized diet that is mainly known for its ability to assist with weight loss. Other speculated benefits of the keto diet are improved health, disease prevention, as well as neurological advantages.
The basis of the ketogenic diet is very simple; very low-carbohydrate, moderate-protein and high-fat. Although individual variances in dietary intake are common, the general trend seems to be a diet consisting of 70-80% fat, 10-20% protein and <10% carbohydrates.
However, it is noted that the diet does not state any desired ratio of macronutrients, or calorie requirement, although it is recommended to consistently consume less than 50 grams of carbohydrates per day.
This is achieved by significantly reducing the intake of foods that contain significant amounts of carbohydrates, while completely removing all forms of processed carbohydrates.
In turn, this leads to the dietary removal of sugar, grains, cereals, starches, and most sauces. Less obvious foods to eliminate are beans, legumes, and most fruits.
Instead, all meals on a ketogenic diet are primarily based around meat, fish, eggs, butter, cheese, nuts, oils, avocados, low-carbohydrate vegetables, herbs and spices.
How Does The Ketogenic Diet Work?
The aim of the keto diet is to induce ketosis - a point where the body switches its primary energy source from glucose to ketones.
Glucose is typically the most used energy source on any diet that contains even a modest amount of carbohydrates. However, in a state of carbohydrate deprivation, and subsequently glucose deprivation, ketone production will be upregulated to be used as an alternative fuel.
Advocates of the keto diet argue that ketones are the natural and desired fuel source in the body, despite glucose being favored over ketones for energy production if both sources are abundant.
The proposed physiological benefit to the keto diet is that by significantly reducing glucose availability, and therefore insulin production, individuals will be able to more efficiently use stored body fat as a fuel source.
The increased utilization of stored body fat for fuel has led to many hypotheses about the keto diet’s benefits for not only fat loss, but also the prevention, or even reversal, of diseases such as diabetes, cardiovascular disease, and cancer.
What Are Ketones?
Ketones are molecules that are produced by the liver from fatty acids. Ketones are a crucial ‘backup’ energy source during times of starvation, especially important back in hunter-gatherer times, when food (carbohydrates in particular) were temporarily unavailable.
After ketone bodies have been produced, they are similarly, yet more inefficiently, metabolized in a similar fashion to glucose; transported to cells, entering energy-producing metabolic cycles, and then oxidized for energy.
Is The Ketogenic Diet Useful For Weight Loss?
Weight loss is dependent on an individual maintaining a negative energy balance for an extended period; consuming less energy (calories) from food than they are expending per day through normal physiological functioning and activity.
As demonstrated in scientific research, any form of dietary restriction will inevitably lead to indirect reductions in energy intake, and therefore body weight, if the user manages to successfully continue this restriction.
Weight Loss Studies
The keto diet is a valuable method in which to create an energy deficit. After all, it is logical to assume that the abstinence of one of only three energy-containing nutrients (protein, carbohydrates, and fat) is bound to cause a dramatic change to one’s overall caloric intake.
Following this, it is no surprise that multiple studies analyzing the effects of have consistently demonstrated its results for weight loss:
- Participants showed an average 2lbs loss after 3 months on a keto diet .
- Participants showed an average 8lbs loss after 6 months on a keto diet .
- Participants showed an average 7lbs loss after 24 weeks on a keto diet .
- Participants showed an average 10lbs loss after 10 weeks on a modified program .
- Participants showed an average 2lbs loss after 6 weeks on a keto diet .
However, it is important to note that the physiological reasons that underpin this weight reduction are not because of the explanations offered by most keto diet advocates.
Common ketogenic reasoning for fat loss is based upon lowering insulin production – a hormone partially responsible for fat utilization - as carbohydrate intake primarily dictates increases in insulin.
Supposedly, this lower circulation of insulin will lead to more body fat being utilized for energy production. This has been termed a “metabolic advantage” which favors a greater utilization of body fat, as opposed to glucose or glycogen (stored carbohydrates), during times of energy deprivation.
Despite this, studies comparing the composition of weight loss of a ketogenic diet versus a carbohydrate-rich diet find undetectable differences in weight loss if calorie intake is similar .
In addition, provided an energy deficit is apparent, differences in insulin secretion between diets are not associated with the extent of weight loss.
It is speculated that the increased thermic effect (energy needed to digest and absorb nutrients) of carbohydrates in comparison to dietary fat may counteract any potential “metabolic advantage” of keeping insulin production low and stable. This is also evidenced in a meta-analysis of controlled feeding studies that showed the significantly greater energy expenditure of lower fat diet plans .
Not to mention that ketogenic diets still have considerable fluctuations in insulin levels from protein intake, which has shown to raise insulin levels to a similar extent than is shown with carbohydrates.
Overall, although the theoretical underpinning of the “metabolic advantage” has arisen scientific experiments to explore this topic, it has not been found to be quantitatively meaningful.
Instead, weight loss is primarily determined by the number of calories ingested, and the resultant energy deficit, as opposed to varying proportions of carbohydrates and fat in the diet.
It Can Help Control Your Appetite
The keto diet may have an advantage over other diet plans in suppressing hunger.
Specifically, ketogenic or low carbohydrate diet plans can increase the production of a hormone called leptin (relative to other diet plans), while decreasing the production of a hormone called ghrelin.
Leptin is a hormone predominantly made by fat cells that helps to regulate energy balance by inhibiting hunger. Conversely, ghrelin is a hormone that is primarily released by the stomach that stimulates appetite, increases food intake and promotes fat storage.
Although data is inconclusive, the actions of these hormones during a ketogenic diet appear to reduce the subjective feelings of hunger throughout weight loss trials to a greater extent than isocaloric non-ketogenic diet plans.
The significance of leptin and ghrelin is crucial when looking at the long-term success of a diet, as it has been demonstrated that weight loss causes changes to appetite-regulating hormones that facilitate weight regain and a return to energy homeostasis.
In turn, the hunger response to weight loss nullifies the success of many dietary approaches in the long-term. This may potentially be avoided with a ketogenic approach.
Weight Loss Vs Fat Loss?
It should be noted that in some studies comparing the weight loss of low-carbohydrate diet plans versus low-fat diet plans (i.e. keto diet programs), weight loss can often be more dramatic in the low-carbohydrate group, especially if the study duration is short (<4 weeks). At first glance this may seem beneficial, although it is essential to differentiate weight loss versus fat loss.
As carbohydrates are necessary in order to store glycogen in muscle tissue, and glycogen is attached to water molecules, a diet such as keto that depletes glycogen stores will also reduce body water content.
This occurrence can happen within a few days of switching to a ketogenic diet, and can easily be mistaken for a sudden drop in body fat if an individual is only referring to the scale to track changes in body composition.
It is key to focus on fat loss when analyzing studies that assess the differences in body composition from either diet, as only considering weight loss will lead to unjust conclusions that do not account for the initial losses in water weight from a low carbohydrate approach.
This is also a key reason why weight seems to be more easily regained on a low carbohydrate diet when carbohydrates are reintroduced (known as “water weight rebound”).
Keto Diet Meal Plan Example
Below we've broken down a typical meal plan for somebody following a keto diet:
- Breakfast: 4 ounces ground beef, mixed with spices, onion, low-carb vegetables, fried in butter or olive oil. Unsweetened herbal tea or coffee with heavy cream.
- Lunch: 4 ounces baked fish with butter sauce. 1 cup cauliflower chopped and sautéed in butter or olive oil. 1 cup salad greens sprinkled with cheese, with a tablespoon of full fat dressing.
- Dinner: 6 ounces pulled pork. 2 cups cabbage in butter. salad greens with high fat dressing
The Potential Benefits Of The Keto Diet
Other than being useful for weight loss, the keto diet can have multiple other positive impacts on your health. Below we've listed the other benefits that are proven by science:
There is also mounting experimental evidence for the keto diet’s broad neuroprotective properties, and data has emerged that supports its use in multiple neurological disease states .
Although the mechanisms of action are unclear, the high dietary fat intake subsequently increases consumption of specific polyunsaturated fatty acids such as EPA and DHA. These fatty acids help regulate brain excitability, reduce inflammation, and decrease the production of reactive oxygen species and cell death rates.
In fact, ketone bodies themselves possess neuroprotective properties by reducing the permeability of mitochondrial membranes, which allows antioxidants to remain in the cell and neutralize any threatening substances .
It is theorized that these are some of the key reasons why the ketogenic is now a well-accepted treatment for helping epileptic patients. Other promising research is available showing its treatment effect in Alzheimer’s and Parkinson’s disease by reducing neuroinflammation .
Elimination of Sugar
A key contributor to the health benefits of a ketogenic diet are because of the removal of sugar.
Although sugar may not necessarily have damaging effects in moderate quantities, the avoidance of its intake can only be praised when reviewing the efficacy of a diet.
Mechanistic studies convey that the metabolism of sugar, specifically fructose, generates substrate for de novo lipogenesis (synthesis of fatty acids from carbohydrate) that may lead to the excess accumulation of fat in the liver .
Frequent sugar intake has also shown to increase biomarkers of chronic inflammation by causing recurrent hyperglycaemic responses and elevated levels of free fatty acids, both of which result in an overproduction of free radicals that may induce vascular damage .
This physiological mechanism may be the reason why epidemiological studies suggests that an overconsumption of sugar increases the risk factors for cardiovascular disease and metabolic syndrome.
Are The Health Benefits Only Because It Helps You Lose Weight?
Despite the health benefits of a ketogenic diet, the beneficial components are mainly as an indirect result of its ability to reduce body weight. This is since the majority of health benefits seen by any diet can be explained simply by weight loss, as body weight is the largest influencer of nearly all health-related biomarkers.
As such, it is hard to assess the isolated health effects of the other components of a keto diet (reduced sugar intake, removal of processed foods etc) when weight loss is having such a large underlying effect during scientific studies.
This creates difficulty in forming a reasonable judgement on any diets impact on overall health outside of weight reduction.
To make a reasonable assessment, the individual aspects of the ketogenic diet (high fat, high cholesterol) need to be individually assessed outside of ketogenic studies where weight loss is not a deterring issue.
Are There Any Risks Associated With Following A Keto Diet?
While there are a whole host of excellent health benefits, but it's not without its flaws. Below we've listed the main health concerns of following a keto diet:
High Intakes of Saturated Fat
Due to the very high amount of dietary fat present in a ketogenic diet, this will likely cause a very high intake of saturated fat – unless the individual purposely focuses on consuming mainly vegetable-based fat sources rather than animal sources.
A diet high in saturated fat has the ability to raise blood cholesterol by reducing the number of LDL-cholesterol receptors in the body, as well as increasing the rate of LDL-cholesterol oxidation (causing inflammation) and arterial plaque formation .
In fact, studies that replace saturated fat intake with the same caloric intake from complex carbohydrates, monounsaturated fat, polyunsaturated fat, and even sugar, find a significantly reduced risk of all types of cardiovascular disease including coronary heart disease and ischemic strokes .
To add to this, saturated fat has direct implications for reducing the capacity and function of beta cells (that produce insulin) which can hypothetically increase the development of type 2 diabetes by affecting insulin production and glucose disposal.
High Intakes of Dietary Cholesterol
Despite cholesterols necessity for cell production, nerve insulation, and maintaining hormonal balance, our bodies have evolved to produce the right amount of cholesterol from other substances when needed. As such, we have no requirement for exogenous dietary cholesterol.
Excess dietary cholesterol can lead to an abundance of the molecule in the blood, potentially creating an accumulation of cholesterol on the artery walls which may affect blood and oxygen flow.
Too much dietary cholesterol intake is also associated with elevated blood cholesterol levels, with the degree of increase gradually lowering as blood cholesterol levels rise from added dietary cholesterol intake .
Excess dietary cholesterol also facilitates fatty deposit build-up on blood vessel walls by the uptake of modified LDL-cholesterol particles, inducing the development of large plaques which are vulnerable to rupture and create arterial blockages .
Is The Avoidance of Carbohydrates Worth It?
A great question to ask when considering the ketogenic diet is what unique benefit does the keto diet offer that warrants the unnecessary restriction of carbohydrates?
After all, as much as the removal of processed sugar is certainly a key benefit to the keto diet, the avoidance of healthy food groups such as beans, legumes, fruits and grains is not justified by any reasonable evidence.
This is especially important when considering the avoidance of these foods makes it harder to access essential nutrients such as magnesium, copper, phosphorus, zinc, phytonutrients, vitamin C, and antioxidants.
Protective substances, although non-essential, such as lignans, phytic acid, saponins, phytosterols and phenolic compounds are also only found in some of these products such as wholegrains.
Is The Ketogenic Diet Suitable For Athletes?
All sporting activity which revolves around strength, speed or endurance will ultimately be heavily reliant on glycogen and glucose availability for maximum performance.
In fact, carbohydrate availability is arguably the key determinant to how well an athlete can perform in their named discipline on any given day.
A lack of carbohydrate stores (glycogen) in the muscle is the major trigger for the onset of fatigue and a reduced power output. This is due to carbohydrate stores being located very close to the mitochondria (energy-producing organelle) and are therefore a fast and efficient preferential source of energy that can support high-energy demands during intense activity.
When carbohydrate stores diminish, such as on a ketogenic diet, fuel utilization turns to fat stores which are more inefficiently used as an energy source and can only support lower level intensities of exercise, hence performance measures significantly decline at this point.
However, there are two potential positives to a ketogenic diet for athletic performance. 1) low carbohydrate protocols are able to further increase endurance training adaptations during low-moderate intensity training sessions, and 2) the ability to reduce body fat can improve one’s strength-to-weight ratio.
The improved endurance training adaptations would appear to be as a result of a heightened ability to oxidize fat at a given exercise intensity, which allows an athlete to spare muscle glycogen for use later in exercise when exercise intensity increases, thus delaying the onset of fatigue.
In other words, it allows for a more efficient usage of energy sources at certain exercise intensities that conserve the ability to perform well later in exercise.
On the contrary, the issue becomes that the longer an athlete remains on a severely carbohydrate restricted diet, the more inefficient they become at utilizing carbohydrate stores when needed. This is due to a downregulation of regulatory proteins involved in carbohydrate metabolism when dietary carbohydrate is restricted for long periods.
For this reason, the ketogenic diet is not a good protocol for any athlete who takes part in high-intensity activity that relies on carbohydrate intake. As the keto diet decreases the ability to use carbohydrates, it is also not an ideal diet for endurance athletes, despite some benefits to enhancing training adaptations.
The Bottom Line: A Highly Beneficial Diet Plan
The ketogenic diet is a very low-carbohydrate, moderate-protein and high-fat; 70-80% fat, 10-20% protein and <10% carbohydrates.
The keto diet is a highly effective way to limit your daily caloric intake, and lose weight overall - this is due to it heavily restricting your carbohydrate intake.
Evidence has shown the keto diet can improve triglycerides, cholesterol, and blood glucose profiles. The keto diet also has a unique neuroprotective benefit and is used in outpatient settings to treat epileptic patients.
However, the nature of diet likely causes a high intake of saturated fat and dietary cholesterol that could increase inflammation and lead to atherosclerosis.
The keto diet is also not ideal for athletes or anyone looking to train at high-intensities due to the removal of carbohydrates which are critical to performance.