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In a world of fast food and fast results, most people don’t want to wait to shed the pounds they seem to pack on so effortlessly during the holiday season. But while an easycome, easy go approach may in other arenas, well-planned health regimens need to be implemented long-term.

Fad diets encourage quick, and seemingly easy weight loss via calorie restriction in general, and carbohydrate restriction in particular. Because glucose is the principal energy source used by the body to fuel us at the cellular level, and the brain relies chiefly on glucose for energy, low-carbohydrate diets are detrimental to health long-term and can cause the body to readjust by slowing the metabolism. Moreover, these diets are not sustainable long-term, and often result in binge relapses, causing the weight to return.

A new trend in the industry is the ketosis diet, which is a high-protein, high-fat, and low-carb diet that forces the body into a state of ketosis, or relying on ketone bodies rather than glucose as a fuel source. While staunch proponents of the diet tote their “ripped and shredded” look as proof that the sugar-shunning ketosis diet is healthy long term and is a viable way to get fit, they disregard the fact that the body needs to maintain certain blood glucose levels in order to survive.

Here are three reasons to avoid the ketosis diet:

1) You Will Damage Your Metabolism.

When the body adapts to periods of long starvation and has depleted its glycogen stores (which is how our body preserves glucose) through the process known as gluconeogenesis, the body switches to a ketogenic pathway in order to preserve muscle tissues from breaking down for glucose conversion. This results in the body running on the breakdown of fatty acids, and an overabundance of acetyl-CoA in cells because unlike amino acids, fatty acids cannot be converted into glucose. Organs such as the brain learn to thrive on ketone bodies as an anti-starvation mechanism.

Keep in mind that there is no way to “trick” Mother Nature. The body adapts to a low-carb diet by producing fewer carbohydrase enzymes to break down carbs and releasing lower amounts of insulin into the bloodstream to take up glucose. In a nutshell, the metabolism suffers. Coming off of the ketosis diet will require some time and effort for the body to readjust and rebuild its metabolism. On the other hand, the body can easily adjust to greater carbohydrate intake, which is why high-carb (at least 50% of caloric intake), and not low-carb diets are recommended by doctors for long-term health—contrary to the “fad diet” plans and products pushed by the diet industry, which will not give lasting results.

2) Long-Term Lifestyle Changes Involve Eating Adequate Amounts of Healthy Carbohydrates.

In order to improve your health with lasting results that are easy to maintain, you must adequately fuel your body with healthy carbohydrates […]

Low calorie, low carb diets are dangerous for long-term health because the body depends on carbohydrates, particularly the sugar glucose, to fuel the chemical reactions in the body through the process of cellular respiration.

Cellular respiration is basically the opposite of photosynthesis. It is a reaction wherein sugar and oxygen are converted into carbon dioxide and water:

C6H12O6 + 6O2 → 6H2O + 6CO2

With the breakdown of glucose, cells generate ATP, which is the “energy currency” molecule that cells rely on. On a diet that is low in carbs, our body will not receive the fuel it needs to function, and if the diet is low in cals, it will also not receive enough nutrients to convert into glucose and will start breaking down fat and muscle tissue in the body, leading to weight loss

3) You Will Go Crazy

Alright, so you lost some weight. Sweet, right?

Not really. Although this may seem desirable at first, because the body isn’t getting an adequate supply of glucose, the brain, which runs exclusively on glucose, will not be able to function properly and you will feel tired, depressed, and for lack of a better word, crazy. In fact, our brain and nerve cells, which weigh a little over a kilogram, consume about half of the total glucose we use every day.[1] The brain cannot use fat for fuel because fatty acids cannot cross the blood-brain barrier. Moreover, deprivation diets are unsustainable, and eventually the dieter will return to their old eating patterns and their old weight.

Simply put, low carb diets are starvation diets.

There are three major steps in cellular respiration: glycolysis, the citric acid cycle, and the electron transport chain. When the cells break down glucose through the process of glycolysis, two pyruvate molecules are produced. These pyruvate molecules can either be built back into glucose, or converted into acetyl CoA molecules to enter the citric acid cycle in the mitochondrial matrices of our cells. The citric acid cycle yields ATP and carbon dioxide, and produces compounds that will release their hydrogen atoms into the electron transport chain. The electron transport chain of the inner mitochondrial membrane then uses the electrons from the hydrogens to combine with oxygen and produce water, meanwhile pumping the protons out into the intermembrane space to make a gradient that will be used to power the synthesis of ATP. This is why glucose is so important.

There are two major dieting trends in the fitness industry at the moment: the Paleo diet, and the ketogenic diet. They are both low carb, high protein diets. 

The ketogenic diet is a high protein, high fat, and low carb diet that forces the body into a state of ketosis, or relying on ketone bodies rather than glucose as a fuel source. While carb-phobic, bacon-and-egg breakfast lovers swear by it religiously, toting their “ripped and shredded” look as proof that the sugar-shunning ketosis diet is healthy long term and is a viable way to get fit, most people don’t fully understand what it means scientifically when the body goes into ketosis.

The body needs to maintain a certain concentration of glucose in the blood in order to survive. After a couple of days of dietary glucose deprivation, the body will also have rid itself of glycogen—the storage form of glucose in the liver, which is used during periods of starvation. Once the glycogen is gone, the body begins gluconeogenesis: making glucose from amino acids, i.e. breaking down muscle tissue. The body cannot rely on gluconeogenesis forever, because this would result in muscle atrophy, but it also cannot convert fat into glucose. During the first few days of fasting, a person will experience dramatic weight loss due to glycogen and protein loss, loss of body fluids, and loss of import minerals.

You may be wondering, why can’t the body just run on fat? Only the glycerol portion (5% by mass) of the triglyceride (fat) molecule can be converted into glucose. Fatty acids cannot be converted into glucose. The breakdown of fat tissues, called fatty acid oxidation, produces acetyl CoA. Acetyl CoA can enter the the citric acid cycle to generate ATP, but it cannot be converted into glucose because the conversion of pyruvate into acetyl CoA is irreversible. After a few days of glucose starvation, acetyl CoA builds up in our cells and ATP generation through the electron transport chain starts to slow. Once this happens, the body will switch from the glucogenic to the ketogenic pathway, by converting acetyl CoA to ketone bodies in the liver. The ketones will then enter the bloodstream and be used in place of glucose. The brain eventually adapts to running on these ketone bodies, which have the solubility to cross the blood-brain barrier so that protein can be conserved. Because there are many areas of the brain that still rely exclusively on glucose, the body continues to sacrifice protein, at a slower rate, even when dietary protein intake is high. Once the body switches from relying primarily on gluconeogenesis to relying on ketone bodies for fuel, the body has achieved a state of ketosis.[2] Symptoms of ketosis include a smaller appetite, fruity “acetone” breath, and acidic urine.

The body needs at least 50–100 g of carbs a day to keep away from ketosis and the brain needs at least 130 g for optimal function. When ketosis kicks in, fasting hormones slow the metabolism and heart rate, body temperature lowers, and disease susceptibility increases. Other side effects include nausea, fatigue, and constipation. The lower production of the hormone insulin is also problematic because insulin is what encourages body cells to intake glucose, and without sufficient insulin, blood glucose remains high. If a person on a ketogenic diet ever does indulge in carbs, blood glucose levels will rise and there won’t be enough insulin to induce the cells to absorb the sugar. Ongoing high blood sugar can lead to health issues. When the dieter returns to eating well-balanced meals that provide adequate nutrition through carbs, fat, protein, vitamins, and minerals, the body will retain these nutrients and the weight will return, often higher than the initial amount. Scariest of all, eventually, ketosis can even lead to impaired vision and organ failure.

Eating high amounts of saturated fat is not recommended because saturated fat is bad for heart health. It promotes blood clotting and increases LDL (low density lipoprotein) blood cholesterol while lowering HDL (high density lipoprotein) levels.[3]

What exactly is meant by LDL and HDL cholesterol? The liver, the major site of lipid synthesis in the body, makes cholesterol and fatty acids. Lipids made in the liver and chylomicron remnants are packaged together as VLDL (very low density lipoproteins) for bodily use. VLDL compounds are mostly triglycerides, but as they move throughout the body and cells intake the triglycerides, the VLDL compounds become LDL compounds, also known as “bad cholesterol.” LDL contains few triglycerides but has a high cholesterol ratio. The liver also makes HDL or “good cholesterol.” These compounds contain low cholesterol and a greater amount of protein. They are made to collect extra cholesterol and return it to the liver for recycling.[4]

Paleo Leap, LLC claims that high dietary cholesterol is a good thing,[5] this couldn’t be further from the truth. LDL blood cholesterol accumulates in the arteries, contributing to plaque (an accumulation of fatty deposits, smooth muscle cells, and fibrous connective tissue along artery walls), raising blood pressure and restricting blood flow, and thus causing cardiovascular disease. In fact, blood cholesterol level is used as a predictor of a heart attack or stroke. According to a final report by the National Cholesterol Education Program, a 1% increase in dietary saturated fatty acids may cause a 2% increase in LDL cholesterol and a 2% increase in heart disease risk. Conversely, a 1% decrease in saturated fats may cause a 2% decrease in LDL cholesterol levels and heart disease risk.[6]

While our bodies do need cholesterol, a crucial component of cell membranes, we cannot simply “eat” LDL or HDL cholesterol; our liver synthesizes the cholesterol we need. The liver makes about 600 mg of cholesterol a day, and it is recommended that dietary intakes do not exceed 300 mg. (As a point of reference, the amount of cholesterol in one egg alone is over 200 mg.) Therefore, adding high amounts of cholesterol to the diet is detrimental to health and can even be deadly. However, there are things that we can do to encourage HDL levels, such as eating foods high in soluble fibre, such as oats. These fibres bind to bile acids, forcing the liver to break down cholesterol to synthesize more bile. Grains, fruits, and vegetables are healthy sources of carbohydrates and contain ample fibre.

The Paleo Diet also encourages eating large amounts of protein, as we would if we were part of a non-industrialized, “hunter” society with a much lower life expectancy. A high protein diet is also promoted by people following the ketogenic diet, and is viewed as healthy by many people in the diet and fitness industries in general. These industries spread the belief that it is impossible to overindulge in high-protein foods because the body does not store excess protein the way that it stores fat, but this is misleading. The body does not directly take protein into the body. When protein is digested, it is broken down into its amino acid components for uptake into our cells, which then make the proteins that they need accordingly. Eating excess amounts of protein will cause a surplus of amino acids in the blood, which are deaminated (their amino groups are removed) and converted into fatty acids or glucose. It is not true that protein builds only muscle and not fat. It is energetically inefficient to convert carbs and protein into fat and much easier to convert excess calories into fat when those calories have come from fat, but any surplus of food—whether protein, fat, or even carbohydrate—will cause you to gain fat.

However, eating a high protein diet has consequences much more dire than weight gain. Deamination of amino acids produces ammonia, which is toxic to the body. To combat high ammonia in the bloodstream, the liver combines ammonia and carbon dioxide into urea for excretion via the kidneys. Eating a high protein diet, especially without drinking large amounts of water, can cause dehydration and is rough on the kidneys. Additionally, too much protein can encourage calcium excretion and cause osteoporosis. High protein diets have also indirectly been linked to heart disease and colon cancer, because these diets tend to be high in animal protein, fat, and cholesterol.[7]

Proponents of ketosis aim for less than 50 g of carbohydrate per day, often eating as little as 10 or 15 g (the amount in a few leaves of spinach). Paleo proponents eat 100–150 g carb for maintenance and less than 50 g for accelerated fat loss.

Both the ketogenic and Paleo diets are pseudoscientific and based on faulty logic; they are dangerously high in fat, cholesterol, and protein, and are much too low in carbohydrates. There is no universe on the material plane of existence in which bacon and eggs constitute a healthy breakfast; it is just not true.

Carbs are good. Because maintaining blood glucose levels is critical to life, the body readily adjusts to using glucose frugally when it is scarce and abundantly when there is a steady supply. Glucose oxidation adjusts to dietary intake of carbohydrates. Although excess glucose can be converted to fat, fat conversion is minimal and, even then, occurs only after glycogen stores have been filled.[8]

A diet consisting of generous portions of complex carbs, a moderate amount of protein, and a low to moderate amount of healthy fats is the most optimal for health.



Whitney E., Rolfes S., Hammond, G., & Piché L. (2013). Understand Nutrition: First Canadian Edition. Nelson.

[1] Whitney et al., 104, 226 – 228.

[2] “How Does the Body Adapt to Starvation?” Khanacademymedicine.

[3] Whitney et al., 147

[4] Whitney et al., 142 – 143


[6] Whitney et al., 164;

[7] Whitney et al., 224, 184 – 191.

[8] Whitney et al., 224.

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