How was the Ketogenic Diet developed?
The Ketogenic Diet was developed in 1924 by Dr. Russell Wilder at the Mayo Clinic as a treatment for childhood epilepsy. It was later replaced by new medications to control seizures in the 1940s. It has become more popular in the past two decades as interest in diet therapies has grown and become more accepted (1). It has since been used to prevent and treat a variety of conditions:
· High blood pressure
· Heart disease
· Type 2 Diabetes
· Alzheimer’s Disease
· Parkinson’s Disease
· Certain types of cancer
What is the Ketogenic Diet?
The Ketogenic Diet is a diet low in carbohydrates, high in fats and moderate in proteins. It is different than the Atkins diet or other low-carb diets because it replaces carbs with fat, instead of just eliminating carbs. By reducing carb intake, you reduce your body’s reliance on carbs for creating energy. Instead, your body goes into a state of ketosis, where your liver turns fat into molecules called ketones. Ketones are high energy molecules that your brain can use for energy. Your other cells start using fat for energy. Typically, the Ketogenic Diet recommends no more than 5% of your diet come from carbohydrates per day (~20-50g) with no calorie restriction.
But isn’t fat bad for you?
In the 1980s, low fat diets were introduced as a way for you to lose weight and improve your health. It was thought that fat made you fat and high cholesterol was caused by eating too much cholesterol. As a result, many low-fat diets and products were created and recommended by health professionals and public health agencies. The general recommendation was to reduce fat intake to no more than 30% of your daily calorie intake.
Low-fat products that are marketed as “diet” or “light” still draw the attention of many consumers who think they are making a healthy choice. They may actually do more harm than good though. These products are typically full of sugar, salt and artificial flavouring which can all have negative health impacts. One of the main jobs of fat in our diet is to give flavour to our food. It gives our brain the signal that something tastes good and this is because we need fat in our diet to survive. We need fat to control our body temperature, absorb fat-soluble vitamins, create hormones, produce energy, protect our organs and provide the building blocks for our tissues. Our body needs fat to function and so we have evolved to consume fat in our diets. When we remove fat from food, we need to replace it with something else that tastes good in order for us to want to eat it. This is where harmful additives are used to replace the fat our body needs.
In the past two decades, a great deal of research has been done on the different types of fats and their health implications. Initially, we found that mono- and polyunsaturated fats were good and trans and saturated fats were bad. This was the basis for whole foods diets that focused on Omega 3 content, such as the Mediterranean Diet. It was found that nuts and seeds, olive oils, avocadoes and fish contained “the good fats” and could reduce our risk of heart disease and inflammatory conditions. It was also recommended that we reduce our intake of other animal products which were high in saturated fats, particularly red meats. As our knowledge of nutrition and its effects on the body have progressed, it has been found that there is no significant difference between the type of fat you eat and health outcomes (29, 30, 31).
The exception to this is trans fats. Trans fats are found in manufactured products and are not naturally present in our environment. They are created by the hydrogenation of oils which turns liquid oils into solids. This increases the shelf life and flavour profile of foods. They are typically found in shortenings and margarines, crackers, cookies and other packaged foods as well as fried foods. These have been shown to have a negative impact on cardiovascular health and consumption has been correlated with heart attack, stroke, heart disease and early death (32).
Avoiding fat is not the answer. Eating whole foods that naturally contain fat is essential to our overall health and well-being. Choosing a variety of foods allows us to consume many nutrients our body requires, including fats.
But what about cholesterol?
One of the other criticisms of the Ketogenic Diet is that it increases cholesterol levels. High cholesterol has been linked to cardiovascular diseases such as heart disease and stroke. We now know that the type of cholesterol and how it acts in the body is actually more important than cholesterol itself.
Cholesterol is a fat-like substance made by your liver. It is also found in foods you eat and is absorbed through your digestive system. It is packaged into particles called lipoproteins that carry cholesterol in the body. There are two types of lipoproteins, high-density lipoprotein (HDL) and low-density lipoprotein (LDL). LDL delivers cholesterol to the cells that use it to create hormones, bile and vitamin D. If your body has more LDL than it needs, it can build up in the walls of your blood vessels to form plaques. As this plaque builds up, the blood vessel becomes narrower which restricts blood flow. This is why LDL cholesterol is linked to heart disease and stroke and why it is known as “the bad cholesterol”. HDL removes cholesterol from your cells and plaques that have formed and takes it back to the liver to be excreted. This is why HDL is known as “the good cholesterol” and benefits your cardiovascular system. The rise in cholesterol on a Ketogenic Diet is usually due to an increase in HDL cholesterol (36, 37) which is actually a good thing.
What are carbs and why should we cut them out?
Carbohydrates are found in starches, grains and sugars such as bread, flour, rice, pasta, beans, potatoes, cereals, fruit and processed sugars. Our bodies break down carbs into glucose molecules that our cells can use for energy. Because we are good at processing carbs, we turn them into glucose very quickly. This causes a spike in blood sugar and this triggers the release of insulin from the pancreas. Insulin is a hormone that acts as a signaling messenger in the body. Insulin allows your cells to take in glucose from the bloodstream to use within the cell. We are also able to store extra glucose as glycogen in the liver and muscles, or as fat in the rest of the body. When insulin is released in large amounts over an extended period of time your cells can become resistant to the signal. This means your body needs a higher level of insulin to move glucose into its cells. At some point, your body cannot maintain these high levels of insulin so glucose builds up in the bloodstream. This is how insulin resistance is related to prediabetes, metabolic syndrome and Type 2 diabetes (2). Poor blood sugar control and obesity are related to many other chronic illnesses such as heart disease, stroke, cancer, high blood pressure and high cholesterol. It is becoming clear that carbs and sugars have a negative impact on our health. Replacing carbs with fat is what the Ketogenic Diet is based on.
What makes the Ketogenic Diet work?
Normally your cells use glucose as their main source of energy. Glucose is a sugar molecule that comes from breaking down carbohydrates and other foods. Our bodies are very good at breaking down carbs into glucose which provides fuel for your cells and systems. If we have more than we need, glucose becomes stored as glycogen in the liver or muscles or as fat. When carbohydrates are not available, glucose and glycogen stores are depleted and the body starts to make compounds called ketones. Ketones are made by the liver by breaking down fat. By restricting your intake of carbs, your body is forced to use ketones for energy and therefore burn fat. The ketogenic diet is based on this natural metabolic process which is called ketosis.
It takes 3-7 days to use up your stored glucose and glycogen and enter ketosis. Ketones are eliminated by the kidneys and excreted in the urine. You can test the ketone concentration in your urine using ketone test strips. This will tell you if you’ve entered ketosis. Another way to tell if you’re in ketosis is by a strong fruity smell in your breath and urine. Some people also notice improvements in mood, brain function and sleep and a decreased appetite.
The Ketogenic Diet is meant to starve your body of carbohydrates to force it into a state of ketosis. It is not meant to restrict calories, fats or proteins. The idea is to shift your metabolism from burning carbohydrates and glucose as its main fuel to burning fat and ketones for energy. This is done by providing it with lots of fats and reducing carb and sugar intake.
What to expect on the Ketogenic Diet
At the beginning, the Ketogenic Diet can be difficult. Your body has been processing carbs as its main fuel source for a long time and you are asking it to suddenly switch to fats. This takes time. It takes a few days for your body to use up its glucose and glycogen stores. Once glycogen is used up, your liver will start making ketone bodies and you will enter ketosis.
What is the Keto Flu?
When first starting a Ketogenic Diet, many people experience “The Keto Flu”. They report fatigue, headaches, cough, runny nose, nausea, irritability and generally not feeling well. This is not a real illness and it is not contagious. Your body is going through withdrawal from sugar and the carbs that act like sugar in the body. It has been suggested that sugar acts similar to drugs in the brain (3). This makes sugar and carbs similarly addictive and your body needs to readjust to not having them. Everyone is different but it usually take 2-7 days to enter ketosis. This doesn’t mean you have adapted to burning fat for fuel yet. It takes a bit longer to become “keto-adapted”. Your body needs to build up its fat converting enzymes and get used to digesting more fat than it did before. Once you have adapted, you will be able to eat more carbs without reverting to them as your main fuel source.
Keto Flu is also caused by electrolyte imbalances. Electrolytes are the substances that allow electrical conduction and energy exchange within the body. These include sodium, potassium, chloride and many others. They are necessary for most metabolic processes. Reducing sugar and salt intake changes our electrolyte balance and this can contribute to many symptoms of Keto Flu. Reducing insulin levels also changes how your kidneys regulate sodium (4). Dehydration can also create electrolyte imbalances. As your body starts to burn fat, water moves into your cells to take its place. This is why many people experience water retention when entering ketosis. Drinking more water can help prevent dehydration from this change in water storage but it can also contribute to electrolyte imbalances because you will excrete more electrolytes when you are urinating more. Other symptoms that might occur during the initial phases of ketosis include muscle cramps, constipation, heart palpitations and reduced physical performance. Ensuring you are taking in electrolytes and drinking lots of water will help prevent the Keto Flu. Fruits, vegetables, nuts and seeds are high in electrolytes and are encouraged on a Ketogenic Diet. Coconut water and broth are other options to improve your electrolyte balance and keep you hydrated.
How do you know when you’re in ketosis?
There are several signs that you have shifted from processing carbs for fuel into the ketosis phase. You will see increased urination because ketones are a natural diuretic. Ketones are excreted in urine and at the beginning your body isn’t used to the high levels of ketones circulating in the blood. This increased urination can lead to dry mouth, increased thirst and potentially dehydration so it’s important to drink lots of water to maintain your electrolyte balance and prevent water retention. Ketones also have a distinct smell which can translate into bad breath. Acetone is one of the ketone bodies that is excreted in saliva and smells like rotting fruit or nail polish remover. These symptoms typically resolve quickly and are not present long term.
The adjustment period to the Ketogenic Diet is temporary but everyone experiences it differently. Once your body is used to burning fat and ketones as fuel, many people start to feel better. Common changes people experience include:
· Fat loss
· More consistent energy levels
· Improved mental clarity and focus
· Reduced appetite
· Feeling fuller longer after meals
· Increased exercise endurance
· Fewer sugar and carb cravings
Who might benefit from the Ketogenic Diet?
There are many conditions that might benefit from a Ketogenic Diet!
- Weight Loss
- Type 2 Diabetes
- Polycystic Ovary Syndrome (PCOS)
- Cardiovascular Disease
- Neurodegenerative diseases
- Athletic Performance
It makes sense that using fat as fuel should promote weight loss, especially in people who have excess fat to lose. The Ketogenic Diet has been shown to promote weight loss more than low-fat diets in obese people (5), adolescents (6), women (7) and men (8).
Low-carb diets have also been shown to reduce hunger compared to low-fat diets (9). This is likely because of the higher protein and fat content and this may make losing weight less challenging and more successful long-term. Fat and protein slow the digestion of food and let you feel fuller longer. Carbs are also more likely to cause blood sugar spikes and drops. This instability is thought to cause cravings, especially for sugar, and increase how often and how much you eat during the day.
Weight loss may be further increased if the fat intake is high in Omega 3 content and red wine in accordance with the Mediterranean Diet (10).
A common trend is that weight loss is most pronounced in the first 6 months on a Ketogenic Diet and becomes less significant past 1 year (11). Fat loss may also be more substantial in men than women but specifically targets abdominal fat (8), which is what might make it so effective for health.
Why is losing abdominal fat so important?
Abdominal fat in particular has been linked to chronic diseases including heart disease (12), diabetes (13) and high blood pressure (13). Abdominal fat, or central obesity, also makes insulin resistance more likely.
Fat held in the abdomen is hormonally active and makes hormones called adipokines that are thought to reduce the body’s tolerance to glucose. Abdominal fat also releases hormones called resistins which further contribute to insulin resistance. The Ketogenic Diet helps control blood sugar levels and reduce abdominal fat which means it is likely helpful for Type 2 diabetes and other conditions related to abdominal obesity.
The Ketogenic Diet also shows more improvement in blood triglycerides, insulin sensitivity, blood sugar control and insulin levels (14) in obese individuals compared to low-fat diets. This may be important for those with Type 2 Diabetes.
When your body senses an increase in blood sugar it releases insulin. Insulin allows your cells to absorb glucose and use it within the cell for energy. When your body is secreting lots of insulin for a long time, the receptors on your cells stop recognizing it. This is called insulin resistance, and is seen in Type 2 Diabetes. The Ketogenic Diet has been shown to improve insulin sensitivity by up to 75% in a small group of people in only 14 days! (15) The Ketogenic Diet has also been shown to improve HbA1c levels (a measure of long-term blood sugar control) better than low-glycemic diets (16) and was shown to allow reduction in diabetic medications (17) as well.
Polycystic Ovary Syndrome (PCOS) also causes insulin resistance and many women experience abdominal obesity and elevated insulin levels. Low-carb ketogenic diets have been shown to improve hormone regulation, promote weight loss, regulate insulin levels and improve fertility (18) in women with PCOS.
The Ketogenic Diet has been shown to decrease total and LDL cholesterol (19) while increasing HDL cholesterol (20). It also improves blood pressure, reduces blood triglycerides and promotes abdominal fat loss (21) which have all been linked to heart attack and stroke.
The Ketogenic Diet is also thought to be effective in reducing difficult-to-control seizures in children (22). This is what it was originally developed for but was later replaced with medications (1). It has become more popular recently as parents are looking for less invasive long-term treatments for their children.
The Ketogenic Diet may also be helpful in controlling tumour growth in some cancer patients (23). This might be because tumours are able to use glucose but not ketones and the body being able to use both. Essentially it starves the tumour while feeding the rest of the body.
Low-carb diets may also be protective to the brain and improve neuron function. Many people on a Ketogenic Diet experience increased mental clarity and focus. This may be useful in the treatment of Alzheimer’s (24) and Parkinson’s disease (25).
The Ketogenic Diet may also be beneficial for some athletes. There may be a small drop in athletic performance as your body shifts from burning carbs to fat for energy. Long term results show increased aerobic endurance and maintenance of muscle mass in high-performance endurance athletes including cyclists (26) and gymnasts (27). These athletes adapt to store and burn fat as a primary energy source and limit the use of carbohydrates for fuel (28). The exception to this is athletes requiring quick bursts of energy such as shot-putters, sprinters or jumpers. Turning fat into energy takes much longer than carbs. Athletes who need quick bursts of energy may benefit from increased carb intake surrounding exercise that involves these explosive movements.
What can you eat on the Ketogenic Diet?
The Ketogenic Diet is ultimately a low-carb diet so carbs and sugars are basically eliminated:
· Starches – pasta, bread, cereals, bagels, flour, wraps, bagels and baked goods
· Grains – corn, rice, quinoa, oats, millet, amaranth, spelt and barley
· Sugars – fruit juices, chocolate, candies, pastries, ice cream, etc
· Fruit except for small portions of berries
· Beans and legumes – peas, lentils, chickpeas, beans
· Root vegetables – potatoes, sweet potatoes, carrots, parsnips, turnips, beets, rutabaga
Many commercial products are also high in sugars and carbs:
· Low-fat, fat-free or diet products – Many products replace fat with sugar, artificial flavours and salt
· Condiments and sauces – Many contain sugars, wheat, corn and other carbs
· Alcohol – Because of the fermentation process, alcohols have high sugar content
· Sugar-free foods or artificial sweeteners – Many of these contain sugar alcohols (ending in -ose or -ol) which act like sugar in the body and can disrupt ketosis
· Milk products – regular milk, skim milk and sweetened yogurts contain lots of sugar
It is also important to limit unhealthy fats:
· Commercial products like mayonnaise, margarine and other spreads
· Trans fats found in packaged and processed foods
· Vegetable oils including sunflower, safflower, soybean, canola, corn and grapeseed oils
So what can I eat then??
Although the Ketogenic Diet may seem restrictive there are still many options available:
· Meat – chicken, turkey, pork, beef, ham, sausage, bacon, steak, lamb, duck
· Fish – salmon, trout, tuna, mackerel, anchovies, herring, sardines
· Eggs – look for pastured, free-range or Omega-3 whole eggs when possible
· Butter and cream – look for grass-fed when possible to increase your Omega-3 intake (link to Paleo)
· Full-fat dairy – sour cream, heavy cream, unsweetened yogurt, unsweetened almond milk, coconut milk
· Cheese – unprocessed hard cheeses including cheddar, goat, cream, mozzarella
· Nuts – almonds, walnuts, cashews, peanuts, Brazil nuts, macadamias, pecans
· Seeds – pumpkin, sunflower, chia, hemp, sesame, flax
· Healthy oils – extra virgin olive oil, coconut, avocado
· Low carb vegetables – asparagus, mushrooms, broccoli, cucumber, lettuce, onions, peppers, cauliflower, tomatoes, zucchini, Brussels sprouts, spinach, kale
· Herbs and spices – garlic, salt, pepper, oregano, basil, cumin, turmeric, ginger, cinnamon
· Coffee and tea
· Broths – beef, chicken, bone
· Fermented foods – pickles, sauerkraut, kombucha, kefir, miso, kimchi
What are the different types of Ketogenic Diets?
The Standard Ketogenic Diet suggests very low carbohydrate intake along with moderate protein and high fat consumption. It recommends 75% of your calories come from fat with 20% from protein and 5% from carbs. This is the type of Ketogenic Diet most studies are based on and the type that is most often recommended for general health and long-term disease prevention.
The Cyclical Ketogenic Diet is similar to the standard version but allows periods of high carb intake. For instance, you might eat 5 consecutive days according to the Ketogenic Diet followed by 1-2 days of high carb intake. The Targeted Ketogenic Diet is even more specific, where high carb intake is added around workouts. These variations are typically used by bodybuilders and high-performance athletes. Increased carb intake may be especially helpful surrounding exercise that involves explosive movements. Turning fat into energy takes much longer than carbs. Athletes who need quick bursts of energy may benefit from these types of diets.
The High-protein Ketogenic Diet also restricts carbohydrates but places more of an emphasis on protein intake. It recommends 60% fat, 35% protein and 5% carbs. Too much protein can prevent or halt ketosis but too little can cause muscle wasting and hunger. Finding the right balance of protein may be helpful for some individuals.
What are the risks of the Ketogenic Diet?
As with any diet, there are risks involved, and you should talk to your healthcare professional if you have concerns. Although there are risks with the Ketogenic Diet in some populations, no adverse effects have been reported in studies with a variety of participants (33). The Ketogenic Diet is typically safe for most people without major health concerns. If you are unsure, talk to a doctor, nutritionist, dietician or naturopath before starting the diet.
Ketoacidosis occurs when blood sugar drops too low for too long and ketone levels become too high. Ketones are acidic in nature. When they build up too much in the blood becomes acidic and pH levels drop. pH is a measure of acidity and your body needs to maintain a normal acidity level to survive. Ketoacidosis is usually seen in Type I diabetics and can be life-threatening. It is also seen with excessive alcohol consumption and starvation. It is a rare side effect of the Ketogenic Diet but it is possible.
Interaction with medications
You also need to be cautious if you are taking medications, especially for diabetes. Certain medications lower your blood sugar levels and so does the Ketogenic Diet. If you are taking medications that affect your blood sugar levels, they may drop too low while on the Ketogenic Diet. This can lead to symptoms of hypoglycemia such as sweating, shakiness, weakness, nervousness, extreme hunger, nausea, dizziness, headache, blurred vision and fast heartbeat.
Medications that affect your liver function may also cause issues on the Ketogenic Diet. Your liver is what turns fat into ketones. If your liver is not functioning well, ketosis may not occur like it’s supposed to. This can lead to serious complications because your body will not be able to create fuel for itself. If you are taking medications you should talk to your healthcare provider before starting a Ketogenic Diet.
Pregnancy and breastfeeding
If you are pregnant or breastfeeding, the Ketogenic Diet may not be for you. Both pregnancy and breastfeeding require massive amounts of energy so you may need to add more calories to your daily intake. Changing how your body produces energy during these periods may have negative effects on you or the baby. It is best to wait until after to start any kind of lifestyle overhaul. You may need to add an extra carbs from fruit when breastfeeding to ensure your body has the resources to produce milk. You should always consult with a healthcare professional before making changes during pregnancy or breastfeeding.
Negative side effects
Some people experience adverse reactions to the Ketogenic Diet but most are temporary:
· Hair loss can occur at the beginning of the Ketogenic Diet and may be a sign of nutrient deficiency. Make sure you are not restricting calories too much and are eating a variety of foods and adequate protein.
· Indigestion and heartburn are also common when you first start eating a high-fat diet. This usually resolves on its own as your body gets used to digesting more fat.
· Itchy skin, also known as the “Keto Rash” has been reported when starting a Ketogenic Diet. This is thought to be due to ketones being secreted in sweat but there are no studies investigating this yet. Reducing the amount of time your skin is exposed to sweat by showering after activity or wearing clothes that absorb or wick sweat from your skin may be helpful.
It was initially thought that low fat diets would be helpful for people with gallbladder disease or gallstones. Your liver and gallbladder work together to digest the fat you eat by creating and storing bile. Gallstones form when the liver and gallbladder aren’t working well. Small crystals form in the gallbladder and turn bile and cholesterol into gallstones. These usually cause abdominal pain when they try to move out of the gallbladder and get stuck in the ducts that lead to the digestive system. In theory, it makes sense to limit your fat intake if the organs that break down fat already aren’t working well but this may not be the case. Eating a low-fat diet may increase gallstone formation (34) and higher fat diets may actually be helpful for gallstones (35). When you eat more fat, your gallbladder has to empty more often to release bile into the digestive system. This increased bile flow may leave less time for stones to form.
People who have had their gallbladders removed are still able to eat on a Ketogenic Diet. They may not be able to digest fat as well because they are unable to store bile in the gallbladder. The liver will still be able to produce bile but it may not be enough to digest the amount of fat they are eating. These people may notice fatty stools which float and are bulky, pale, oily, foul-smelling and difficult to flush. Gradually increasing the amount of fat you consume may help your body adjust.
Tips for Success on the Ketogenic Diet
Drink lots of water – Ketones are naturally dehydrating since they are excreted by the kidneys. It is important to drink lots of water to prevent the electrolyte imbalances, muscle cramps, constipation and fatigue that some people experience when starting a Ketogenic Diet.
Clear out your kitchen – Carbs and sugars will likely be found in many foods that you use to eat before starting a Ketogenic Diet. Shifting away from a carb-based diet can be difficult and many people crave carbs and sugar at the beginning. Removing these foods from your house will make giving into these cravings less tempting.
Support – Enlist the help of friends, family members and coworkers to help make you successful. Telling others about your goals helps keep you accountable and will increase your rate of success. Having a non-judgmental support system will help you stay on track.
Read ingredients labels – The more processed foods you can avoid the better, but it is important to read ingredients labels when they are available. Look for hidden sources of sugars and carbs as they may not always be obvious. You should also take note of the serving size if you’re looking at carb content since it can be misleading and you may be consuming more carbs than you realize.
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