What is ketosis and how does a keto diet work?
The keto diet is picking up speed as one of the go-to diets for losing weight. It works by putting your body into a state of ketosis, which means that you start using fat for energy as opposed to carbs, the body’s usual energy source. By using up fat from the foods you eat, and the fat reserves within the body, the keto diet can improve overall health and help you lose weight. Here, we’ll go through exactly what ketosis is, its associated health benefits and health risks, and how it can help you lose weight in both the long and short-term.
What is ketosis?
The cells in your body use glucose, or sugar, as their main source of fuel. This glucose is stored as glycogen in your liver and muscles and comes from carbohydrates in your diet. When your carb intake is low, your glycogen stores are reduced, which lowers the levels of insulin in your body. This means that fatty acids can be released from the fat stores in your body, which puts your body through ketosis.
When you reach a state of ketosis, it means that your body is producing an increased number of ketones, which are small fuel molecules produced by the liver from fatty acids. These ketone bodies are water-soluble and are comprised of acetoacetate, beta-hydroxybutyrate, and the spontaneous breakdown product, acetone. Your body naturally produces these molecules when it goes through periods of fasting, starvation, prolonged intense exercise, or very low to zero-carbohydrate diets. In some cases, they can even be produced through alcoholism or in untreated type 1 diabetes.
The ketones are then picked up by extrahepatic tissue outside of the liver, where they’re converted into acetyl-CoA, which is a molecule that is involved in metabolising of proteins, carbohydrates, and lipids. This then enters the citric acid cycle where it’s oxidised in the mitochondria and used for energy. Ketone bodies are also used in the brain to make acetyl-CoA into long-chain fatty acids, which are essential for normal brain structure and function.
What is the keto diet?
As your body produces ketones through a lack of carbohydrates, a keto diet contains little to no carbohydrates and high levels of fat and protein.
Types of keto diet
There are a few different types of the ketogenic diet, which are:
- Standard Ketogenic Diet (SKD): This is a low-carb, moderate protein, and high-fat diet. A normal, “balanced” diet is usually comprised of 30% fat, 20% protein, and 50% carbohydrate. An SKD diet contains 75% fat, 20% protein, and only 5% carbs.
- Cyclical Ketogenic Diet (CKD): As the title suggests, this involves going through cycles of ketosis throughout the week. This could include 5 ketogenic days followed by 2 high-carb days every week.
- Targeted Ketogenic Diet (TKD): This diet puts your body into ketosis throughout the day, and allows you to eat carbs to fuel any workouts you do.
- High-protein Ketogenic Diet: This is similar to the SKD, but includes more protein, at a ratio of 60% fat, 35% protein, and 5% carbs.
What to eat on a keto diet
To reach ketosis, you should eat zero carbs, or as few as you can. The general rule is to limit your carbohydrate intake to under 50 grams per day—ideally below 20 grams. The fewer carbs you eat, the quicker you reach ketosis and more effective the diet will be.
The foods you should eat on a keto diet include:
- Fats and oils: Try and get your fat from natural sources. Good examples include coconut oil, olive oil, avocado, and chia seeds.
- Protein: Organic, grass-fed meat is best, and you can reach daily protein intake from poultry, beef, pork, fish, lamb, and egg. While it is difficult to have a vegetarian or vegan keto diet, you can get your protein sources from seitan, tempeh, and tofu.
- Vegetables: Leafy greens such as spinach and kale, as well as veggies grown above the ground, like broccoli and cauliflower, are best for a ketogenic diet.
- Dairy: While dairy is fine to eat as part of a keto diet, it’s best to go full-fat. Hard cheese, full-fat cream, and butter are the most common forms, while things like full-fat coconut milk and creams can also be used.
- Nuts and seeds: These are an excellent source of healthy fats, with some of the best options being sunflower seeds, pumpkin seeds, macadamias, walnuts, and almonds.
The foods you should avoid on a keto diet include:
- Fruit: While berries are okay to eat in moderation, you should avoid other fruit.
- Grains and starches: These are high in carbohydrates, so avoid things like wheat, rice, rye, oats, corn, quinoa, and everything similar. This includes grain products, like cereal, bread, and pasta.
- Root vegetables: Veggies that grow beneath the ground are high in carbs, so avoid things like potatoes, carrots, parsnips, turnips, and beets.
- Legumes: Legumes tend to be high in starch, so you should avoid them. Foods that fall into this bracket include chickpeas, peas, lentils, and beans.
- Sugar: Avoiding sugar can help you reach a state of ketosis, as your body won’t be relying on sugars as a fuel source. This includes natural sugars such as honey, maple syrup, and agave.
What are the health benefits of a keto diet?
Because the keto diet uses ketones as a fuel source, your body has to rely on its fat sources for energy. This lowers the level of insulin—the hormone that stores fat—which increases the level of fat burning. The level of weight loss may seem drastic at first, however, this is a result of lost water weight as you’re cutting down on carbs in your diet. The carbohydrates you eat and that are stored in your body retain water, so this initial weight loss is simply getting rid of this.
As you are cutting out carbohydrates from your diet, you can find yourself loading up on whole foods and healthy fats, which provide a much steadier supply of energy and leave you feeling fuller for longer. This eliminates sugar highs and crashes, as well as any hunger pangs between meals. Research has suggested that a ketogenic diet can suppress hunger, making it easier to lose weight and keep it off.
When your body reaches ketosis, it can increase the numbers of high-density lipoproteins, which are known as HDL. This is a molecule that transports cholesterol around the body and collects the cholesterol not being used by cells to bring back to the liver to be destroyed. This stops arteries from getting clogged, maintaining a healthy heart, and gives HDL the nickname of “the good cholesterol”.
A low-carb diet can also increase the size of low-density lipoprotein (LDL) molecules—another cholesterol transporter—while reducing the concentration. Larger LDL molecules are considered healthier for the heart, as they can carry more cholesterol around your body than smaller sized molecules. But LDL is known as “the bad cholesterol”, as there is a strong correlation between a high number of LDL molecules and the risk of cardiovascular disease. A state of ketosis can both decrease the numbers of LDL cholesterol and increase the size of the molecules, reducing the risk of a heart attack.
Improved mental performance and increased energy
Ketosis provides a steady flow of ketones to the brain, as opposed to a sharp increase in energy which happens when your body relies on carbohydrates for energy. When in a state of ketosis, the brain doesn’t rely on dietary carbs and is instead fueled by ketones, allowing you to avoid sugar highs and crashes, and even improving focus and concentration.
Similarly, a steady flow of ketones to fuel your body means that your endurance is increased. A supply of carbohydrates is only worth a couple of hours of intense exercise, whereas fat equates to significantly more than this. The keto diet focuses on the fat stored around your body, encouraging weight loss while providing enough energy to keep you going during training and competitive sports.
Are keto diets safe?
As with all diets, there are health risks if not approached sensibly. Because you’re making such a drastic and sudden change to your eating habits, it can take some time for your body to adapt. Many people experience flu-like symptoms, which can range from headaches and fatigue to constipation, cramps, and heart palpitations. This is such a common side effect that it has been nicknamed the “keto flu”. However, these symptoms are generally the result of dehydration, which happens as you suddenly shed water weight. Ensuring you drink enough water and salt can combat the severity of these symptoms.
Other potential risks of adopting the keto diet include developing kidney stones, decreased bone mineral density, suffering gastrointestinal distress, and even becoming deficient in vitamins and minerals. Because of the high-fat nature of the diet, it’s also much easier to increase your intake of the unhealthy trans and saturated fats. It’s important to keep an eye on the source of all your fat sources while on the keto diet.
Keto diets when diabetic
If you’re diabetic, it is possible for you to take on a keto diet, but you should keep an even closer eye on your blood sugar levels, especially at the start of the diet. Always consult your doctor before making any decisions on this.
Studies have shown that cutting carbs lowers blood sugar and insulin levels. One study of people suffering from type 2 diabetes found that 95% of participants reduced or eliminated their insulin medication within six months of following a ketogenic diet. In some cases, a ketogenic diet can even reverse the severity of type-2 diabetes.
If you have type-1 diabetes, you may find that a ketogenic diet halts the progression of it getting any worse, and reduces your need for insulin. However, it’s very unlikely that your diabetes will ever be reversed. In cases where patients are able to continue to produce at least some insulin, it can be possible for them to completely come off insulin medication, with the help of ketogenic diet management and under the advice of a healthcare professional.
Keto diets while pregnant
Some healthcare professionals may advise against starting or maintaining a ketogenic diet through pregnancy. However, there are specialists who agree that it’s completely safe to eat a keto diet while pregnant, provided that you were already on the diet before falling pregnant. It’s best to start a keto diet at least 3 months before trying to conceive, so your body has already adapted to the fat changes by the time you fall pregnant.
According to Dr Michael Fox, fertility specialist at the Jacksonville Center for Reproductive Medicine, regular snacking on keto-approved foods can decrease the rates of miscarriage, preeclampsia, gestational diabetes, and morning sickness. He explains: “Nausea is a reactive hypoglycemic reaction to the dramatically increased insulin resistance caused by pregnancy hormones.”
Keto diets while breastfeeding
While a ketogenic diet is fine throughout pregnancy, you should avoid eating a low-carb diet while breastfeeding. This is because you can lose up to 30 grams of sugar a day via the milk, which you will need to replenish in your own body to avoid the risk of slipping into ketoacidosis. Even though this is extremely rare, it could be fatal if your body is not getting enough sugar.
Ketoacidosis, or diabetic ketoacidosis (DKA), is a complication that can arise from type 1 diabetes. It happens when there are dangerously high levels of ketones and blood sugar, which then makes your blood too acidic, damaging the normal functioning of your organs. It’s almost impossible to develop ketoacidosis if you’re a healthy person on the keto diet, as there is only potential for it happening if you go without any food for several days. Your body can go into a state of ketoacidosis once your blood ketone levels increase above 3.0mmol/L. For a normal state of ketosis, your blood ketone levels should read between 0.6-1.5mmol/L.
Symptoms of ketoacidosis can appear quickly and include:
- Sudden need to urinate
- Extreme sudden thirst
- High blood sugar levels
- High levels of ketones in your urine
- Feeling nauseous or vomiting
- Abdominal pains and cramps
- Extremely bad breath
- Rapid breathing
- Extreme and sudden dry mouth and skin
Ketoacidosis is considered a medical emergency, so if you think you’re experiencing it, you should call your local emergency services immediately.
How do I know if my body is in ketosis?
The best way to tell if your body is in a state of ketosis is to check your urine, blood, or breath. You can buy home kits online that allow you to test these things, and what level of ketosis you’re in. This can also help you keep track of the ketones in your body, and if you do wind up slipping out of the normal state of ketosis, you can adjust your diet yourself. Testing your ketones at home can also help you notice any irregularities before you notice any physical changes.
But there are symptoms you experience when your body first starts producing more ketones than you’re used to. These are similar to ketoacidosis but are just a sign that your body is adjusting to the initial increase in ketones. You’ll be able to distinguish the difference between the symptoms once you’re in ketosis.
Some common symptoms of ketosis are:
- Dry mouth and increased thirst
- Increased urination
- “Keto breath” – this is due to the acetone leaving your body via your breath. Your breath can range in smells, from fruity, to similar to nail polish remover.
- Reduced hunger
- Increased energy and focus
These symptoms, aside from reduced hunger and increased energy, are only temporary and will decrease as your body gets used to being in ketosis.
Will I lose muscle on a keto diet?
There are misconceptions about muscle on the keto diet, mainly that you need carbohydrates to produce them. This isn’t the case—the only things you need to build muscle are sufficient protein, a calorie surplus, and the right training.
Carbohydrates are good for building muscle, as they restore glycogen in the muscle. Training with carbohydrates means that you’re adding more mass to your weight, but only because you’re gaining fat. This is why many bodybuilders “cut” to shed body fat for a lean physique.
However, a keto diet gives you the same energy needed to build muscle, and a low-carb diet can help to prevent muscle breakdown by providing an adrenergic stimulus to your body. This is because when blood sugars are low, your body releases adrenaline which stops muscle proteins from being broken down.
Building muscle on a ketogenic diet increases the lean mass you put on, without the extra fat—as long as you eat the right amount of protein.