THE KETOGENIC DIET​: A SCIENTIFIC REVIEW ON ITS EFFICACY AND SAFETY​

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According to the US Department of Labor, the demand for personal trainers is expected to increase faster than the average for all occupations (US Department of Labor, 2018). This increasing demand for personal trainers is in large part due to the escalation of obesity, diabetes, and various chronic diseases. Chronic disease has become the leading cause of death and disability in the United States, accounting for 70% of the deaths (Clark, Lucett, & Sutton, 2014). The number one killer in America being heart disease claims an average of 635,000 lives per year (CDC, 2017). Of America’s 15 leading causes of death, 14 out of 15 can be prevented, treated, and/or even cured simply by altering one’s daily lifestyle choices (Greger, 2012). With this in mind, it is the role of a personal trainer to advocate for these healthier lifestyle choices and inform clients about potential threats to their health and well-being as it pertains to the trainer’s scope of practice.

As a personal trainer, the ketogenic diet comes up a lot in conversation. The following review of the keto diet is in regards to its efficacy and safety. In order to be a competent trainer, it is my opinion that diets which appear to be fad in nature should be thoroughly investigated before the promotion of that diet ensues. The objective of this entry is to determine whether the keto diet should or should not be actively promoted. It is also important to note that, as with any major changes in diet, one should consult with a physician or dietitian to closely monitor any biochemical variation after starting the regimen (Harvard, 2018).

WHAT IS THE KETO DIET?

Browse anything fitness and it won't be long before you hear someone talking about “keto.” It seems to be all of the rage these days. With promises of rapid weight loss, many people have taken up the diet as a means to reduce some extra poundage. But, what exactly is the keto diet and how does it work?

The Ketogenic Diet, or more commonly referred to as the keto diet, is a diet in which one consumes high amounts of fat and low amounts of carbohydrates in order to enter a state of ketosis (Gustin, n.d.; Harvard, 2018). Typically, the main source of energy for all cells in the body is glucose. The brain demands the most glucose in steady supply since it cannot store the simple sugar (Harvard, 2018). When one is in a fasting state or consuming very little carbs, the body first pulls stored glucose from the liver and temporarily breaks down muscle to release glucose. If this continues for 3-4 days and stored glucose is completely depleted, blood levels of a hormone called insulin decrease, and the body begins to use fat as its primary fuel. The liver produces ketone bodies from fat, which can be used in the absence of glucose (Harvard, 2018; Paoli, Rubini, Volek, & Grimaldi, 2013). When the ketone bodies accumulate in the blood, this is called ketosis (Harvard, 2018).

Unlike the infamous Atkins or South Beach low carb diets, the keto diet is not particularly high in protein. The protein requirement for the ketogenic diet is right in line with the Recommended Daily Allowance and the Acceptable Macronutrient Distribution Range, which is approximately 10% to 35% of one's total calories consumed (Clark et al., 2014; Harvard, 2018). Fat is the cornerstone of the keto diet (Gustin, n.d.) While there are different macro ratio expressions for the diet depending on how strict one is attempting to be, the macro ratios usually range from 70%-80% of calories from fat, 5%-10% of calories from carbohydrates, and 15% to 25% of calories from protein (Estrada, 2018; Gustin, n.d.; Harvard, 2018)

KETO EFFICACY

Weight Loss

When it comes to short-term weight loss, there is an ample amount of evidence to support the use of low carb diets (Bueno, De Melo, De Oliveira, & Da Rocha Ataide, 2013; Paoli et al., 2013). Some studies have even shown that an ad libitum (eat as much and as often as desired) low carb, high protein diet can yield a greater amount of weight loss when comparing it to other diets (Brehm, Seeley, Daniels, & D’alessio, 2003; Paoli et al., 2013). While some might say that this phenomenon is due to an increase in energy expenditure, there has been no direct experimental evidence to support this intriguing hypothesis. On the contrary, a recent study reported that there were no changes in energy expenditure associated with a very low carbohydrate keto diet (Paoli, Grimaldi, Bianco, Lodi, Cenci, & Parmagnani, 2012; Paoli et al., 2013) According to researchers, the weight loss experienced can be attributed to a decrease in calorie consumption due to three agreeable factors (Astrup, Larsen, & Harper, 2004; Harvard, 2018; Johnstone, Horgan, Murison, Bremner, & Lobley, 2008; Paoli et al., 2013):

• Protein and fat have higher satiating effects.

• Ketone bodies have an appetite surpassing nature.

• Appetite stimulating hormones, such as insulin, decrease.

It’s also important to note that when comparing the ketogenic diet to other low carb diets there is no significant difference in weight loss amongst the groups (Johnston, Tjonn, Swan, White, Hutchins, & Sears, 2006). Furthermore, studies that have investigated the diet in a long-term setting have found that there is either no significant difference between the ketogenic diet and conventional weight loss strategies or they have found that the keto diet falls just short in terms of weight loss and mood state (Brinkworth, Buckley, Noakes, Clifton, & Wilson, 2009; Stern, Iqbal, Seshadri, Chicano, Daily, McGrory, & Samaha, 2004; Wycherley, Brinkworth, Keogh, Noakes, Buckley, & Clifton, 2010).

Additional Keto Benefit Claims

Additional benefits proposed by the ketogenic diet include improvements in neurological conditions such as epilepsy, an increase in cognitive ability in healthy individuals, and an improved physical performance in athletes (Gustin, n.d.).

Neurological Conditions

In the case of neurological conditions such as epilepsy, Alzheimer’s, Parkinson’s, and brain trauma, the ketogenic diet is showing to perhaps be a promising treatment (Paoli et al., 2013). One contributing factor that may aid in these scenarios is the elevated levels of β-hydroxybutyrate, one of the three primary ketone bodies found during ketosis (Masino & Rho, 2012; Reger, Henderson, Hale, Cholerton, Baker, Watson, & Craft, 2004; Ross, Swaiman, Torres, & Hansen, 1985). This particular ketone body has been shown to protect the neurons in those who suffer from Alzheimer’s and Parkinson’s disease (Kashiwaya, Takeshima, Mori, Nakashima, Clarke, and Veech, 2000; Rho & Stafstrom, 2012). Although encouraging data has been collected, “at the present time the real clinical benefits of ketogenic diets in most neurological diseases remain largely speculative and uncertain, with the significant exception of its use in the treatment of convulsion diseases” (Paoli et al., 2013).

Cognitive Improvement

It appears that the advantageous effects of the ketogenic diet in individuals with neurological pathologies have led many healthy humans to believe that there are cognitive benefits under normal circumstances. In reality, the research is substantially lacking (Metzelaar, 2018). The studies that do exist on the matter often show that a keto diet is not efficacious at all in regards to cognitive improvements. Delving further into the research, some studies have contrastingly shown that the ketogenic diet decreases cognitive function, with one study even going as far as to state that “a high-fat, diet is detrimental to the heart and the brain in healthy subjects” (Holloway, Cochlin, Emmanuel, Murray, Codreanu, Edwards, & Lambert, 2011; Murray, Knight, Cochlin, McAleese, Deacon, Rawlins, & Clarke, 2009; Zhang, Mckeown, Muldoon, & Tang, 2006).

Increase Physical Performance

When it comes to improved physical performance, the evidence appears to be more ubiquitous and the efficacy slightly better supported than the previous assertion. With that said, there are limits to a ketogenic diet’s effectiveness on performance. Since the ketogenic diet greatly reduces the amount of glucose, and thus glycogen, in the body, anaerobic performance is limited (Phinney, 2004; Zajac, Poprzecki, Maszczyk, Czuba, Michalczyk, & Zydek, 2014). Anaerobic performance includes activities which use anaerobic glycolysis as a means to produce energy. Most gym workouts fall into this category (Clark et al., 2014). Anaerobic activity is short-lived, usually lasting approximately 30 to 50 seconds, due to the production of lactic acid (Clark et al., 2014; ISSA 2018). On the other hand, the ketogenic diet has exhibited positive correlations in regards to endurance training. This is because endurance is largely dependent on the oxidative system. This is the system in which fat can be broken. The first step in the oxidation of fat is a process referred to as β-oxidation. During β-oxidation, triglycerides are broken down into smaller subunits called free fatty acids (FFAs). The purpose of this process is to convert FFAs into acyl-CoA molecules, which are then available to enter the Krebs cycle and ultimately lead to the production of ATP, or energy (Clark et al., 2014). Since fat is the cornerstone of the ketogenic diet, endurance activities benefit significantly due to their ability to exploit the oxidative system (Cox, Kirk, Ashmore, Willerton, Evans, Smith, & King, 2016; Gustin, n.d.; Rhyu & Cho, 2014; Zajac et al., 2014).

KETO SAFETY

When it comes to the safety of a particular diet, it is important to note that anecdotal evidence holds no merit. For every individual who has said wonders about a particular diet, there has been a counterpoint story of someone who has derailed their health because of that same diet. This can also be said about the ketogenic diet. The following is not a collection of anecdotes but rather an analysis of the scientific literature over certain adverse reactions attributed to the ketogenic diet. In order to determine the suggestibility of a diet, it is essential to explore the possible dangers of that diet as to provide one’s clients with the highest degree of service and to avoid potential complications as it pertains to the trainer’s scope of practice.

Kidney Stones

Kidney stones appeared to be a small but notable occurrence amongst studies involving the ketogenic diet. Most of the studies that recorded kidney stone occurrences were found in epileptic children (Denke, 2001; Harvard, 2018; Sampath, Kossoff, Furth, Pyzik, & Vining, 2007). This was due to the presence of hypercalciuria. Oral potassium citrate was provided as an intervention to the children and acted as a preventative measure (Sampath, 2007). Other methods of reducing the chance of kidney stones on the ketogenic diet include staying well-hydrated and magnesium (Phinney, n.d.).

Impaired Concentration, Cognition, and Mood

Ironically, the ketogenic diet’s efficacy in the realm of desirable cognitive improvements not only fails but produces a contrasting effect. Diets that are low in carbohydrates and high in fat, especially trans fat and saturated fat, adversely affect cognition (Parrott, & Greenwood, 2007). In rats, the ketogenic diet has demonstrated deleterious effects in learning and memory (Murray et al., 2009; Winocur & Greenwood, 2005). Translating these experimental methods over to humans, researchers found similar results. Cognitive tests showed impaired attention, mood, reaction time, and a deterioration of cognitive functions that require higher order mental processing and flexibility in healthy humans (Brinkworth et al., 2009; Holloway et al., 2011; Edwards, Murray, Holloway, Carter, Kemp, Codreanu, & Clarke, 2011; Wing, Vazquez, & Ryan, 1995). If improved cognition is the objective, researchers advise that a diet with less fat, saturated fat and cholesterol, and more carbohydrates, fiber, vitamins (especially folate, vitamins C and E, and beta-carotene), and minerals (iron and zinc) should be followed not only to improve general health but to also improve cognitive function (Ortega, Requejo, Andrés, López-Sobaler, Quintas, Redondo, & Rivas, 1997).

Nutrient Deficiency and Disordered Mineral Metabolism

It’s important to note that there is not a single diet that can be prescribed to eliminate the risk of nutritional deficiencies. All diets that lack a variety of foods can lead to an inadequate intake of essential vitamins and minerals. Regardless of the person or particular diet, it is advisable to receive annual screenings to thwart any deficiencies that may arise from the ingestion of routine foods. With that said, the following are nutritional deficiencies that seem to emerge the most in the ketogenic diet: thiamine (Hoyt & Billson, 1979), vitamin D and calcium (Kang et al., 2004), selenium (Bergqvist, Chee, Lutchka, Rychik, & Stallings, 2003), and vitamin C (Willmott & Bryan, 2008).

Osteopenia and Osteoporosis

Bone complications are another concern that ketogenic dieters may want to make note of. Demineralization of bones occurred in a number of studies surrounding epileptic patients (Bergqvist, Schall, Stallings, & Zemel, 2008; Freeman, Veggiotti, Lanzi, Tagliabue, & Perucca, 2006; Kang et al., 2004). One study even found that osteopenia could be found in patients after the first 4 weeks of implementing the ketogenic diet. Additional doses of calcium and vitamin D can prevent the progression of osteopenia and osteoporosis while on the ketogenic diet (Kang et al., 2004).

Disturbances in Heart Health

Being the leading cause of death in the United States, extra emphasis should be placed on reducing the number of risk factors associated with heart disease. While some may believe that dietary cholesterol and saturated fat do not elevate levels of cholesterol in the body, the fact of the matter is that this is just simply not true (Clarke, Frost, Collins, Appleby, & Peto, 1997; Sacks, Donner, Castelli, Gronemeyer, Pletka, Margolius, & Kass, 1981). The mechanisms by which high cholesterol causes and furthers the development of heart disease have been well documented (American Heart Association, 2016; CDC, 2015; National Institute of Health, 2017).

Cholesterol effects heart and artery disease by first initiating with an injury. Major contributors to arterial injury are free radicals. These unstable particles pull electrons from the lining of the artery wall and cause damage. Oxidized LDL, also known as bad cholesterol, is one of these reactive particles that is a well-established cause. In fact, the higher your LDL, the more likely it is to oxidize and cause damage (Rong, Rangaswamy, Shen, Dave, Chang, Peterson, Sevanian, 1998). In the absence of LDL the injury would heal as normal but, following this injury, white blood cells build up around the damaged area and consume passing-by cholesterol. The white blood cells that engulf the cholesterol are known as foam cells and they become grossly engorged due to little negative feedback of uptake. The overfeeding leads to a diminished capacity to migrate, which results in further progression of the disease. The final step in this lethal line up is a rupture or thrombosis. Thrombosis is the main cause of heart attack death. “Dying macrophages release their lipid content and tissue factor, leading to the formation of a pro-thrombotic necrotic core, a key component of unstable plaques that contributes to their rupture and the ensuing intravascular blood clot that underlies myocardial infarction and stroke” (Moore, Sheedy, & Fisher, 2013).

In regards to the ketogenic diet, there is no denying that it increases LDL (Bueno, 2013). Knowing the process by which heart and artery disease occurs, it would only make sense for the ketogenic diet to show an increased risk of cardiovascular disease and it does. Several studies ranging from population studies to diabetes studies to epilepsy studies to metabolic studies to weightless studies to children studies and more all show an increased risk of coronary heart disease, cardiovascular disease, and hypercholesterolemia (Coppola, Natale, Torino, Capasso, D’Aniello, Pironti, & Verrotti, 2014; Kang, Chung, Kim, D., & Kim, H.,2004; Lagiou, Sandin, Lof, Trichopoulos, Adami, & Weiderpass, 2012; Sirven, Whedon, Caplan, Liporace, Glosser, O’dwyer, & Sperling, 1999; Snell-Bergeon, Chartier-Logan, Maahs, Ogden, Hokanson, Kinney, & Rewers, 2009; Yancy, Olsen, Guyton, Bakst, & Westman, 2004).

Increase in All-Cause Mortality

Probably the most disturbing association found to be connected with the ketogenic diet is all-cause mortality. In 2013, a group of researchers aimed to identify how low-carbs diets could help a worldwide epidemic of obesity and cardiovascular disease. The team included 17 studies for a systematic review, followed by a meta-analysis using pertinent data. The studies were comprised of population sample sizes ranging from 647 to 129,716. The researchers found that low carbohydrate diets were linked to a significantly higher risk of all-cause mortality (Noto, Goto, Tsujimoto, & Noda, 2013). Furthermore, a 2014 follow up study to two different long-term studies found that greater adherence to a low carbohydrate diet high in animal sources of fat and protein was associated with higher all-cause mortality as well (Li, Flint, Pai, Forman, Hu, Willett, & Rimm, 2014). In a completely different study, researchers found that a median intake of 14% animal protein was sufficient enough to significantly increase the risk of all-cause mortality (Song, Fung, Hu, Willett, Longo, Chan, & Giovannucci,2016).

Additional Concerns (Diabetes)

The previous pathologies associated with the ketogenic diet were some of the more significant complications found. As research continues to grow a better understanding of the diet and its safety will come to light. Unfortunately, the trends in science are not looking up for this low carb, high-fat diet. Many have recommended the diet to diabetes patients thinking that the low levels of glucose will improve their circumstances. This, however, may not be much of a cure for the disease but rather a treatment for its symptoms. In August 2018, researchers found evidence that a ketogenic diet caused selective hepatic insulin resistance in mice (Grandl, Straub, Rudigier, Arnold, Wueest, Konrad, & Wolfrum, 2018). Hepatic insulin resistance is the impaired suppression of glucose production by insulin in hepatocytes that can lead to hyperglycemia (Meshkani & Adeli, 2009). This hepatic insulin resistance lead to the ketogenic diet group having notably worse signs of blood glucose control than the counterpart group who consumed a high carb, high-fat diet (Grandl, 2018). Prior to this, a team of researchers established that chronic high-fat diets can lead to the apoptosis (cell death) of β-cells in the pancreas (cells that release insulin), which can lead to hyperglycemia. The loss of β-cell mass by apoptosis contributed to the progressive β-cell failure in Type 2 Diabetes (Cunha, Igoillo-Esteve, Gurzov, Germano, Naamane, Marhfour, & Marselli, 2012).

Conclusion

As stated earlier, it is the role of a personal trainer to advocate for healthier lifestyle choices and inform clients about potential threats to their health and well-being. While the ketogenic diet may appear to be advantageous for an initial jumpstart to weight loss, it raises a considerable amount of concern for safety. Chronic disease is the leading cause of death in the nation and the ketogenic diet has only thoroughly demonstrated its ability to treat one affliction that doesn’t make it anywhere near the list of America’s 15 deadliest diseases. On the other hand, it has been positively correlated with three of our top 10 killers including heart disease, stroke, and diabetes. One who partakes in the ketogenic diet, or any other low-carb diet for that matter, should participate in health screenings regularly. Without having the resources or credentials to continuously check biomarkers for health, it would seem negligent to actively promote a diet that can lead to impaired cognition, bone complications, heart disease, all-cause mortality, diabetes, and more.

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