The Ketogenic Diet: What is it, How does it Work and Why?

Thinking about going on the keto diet? You’re not alone! It’s quickly gaining popularity as a weight loss diet. Actually, it has been used for years in a clinical sense to help alleviate symptoms of neurological symptoms.


You may have heard the expression: “Fats burn in the carbohydrate flame.” There is a lot of misinformation about low-carb diets; some claim that it is the optimal diet, while others consider it unsustainable and potentially harmful.


Low-carb diets have been shown to be effective in over 20 scientific studies and have been around for decades. In fact, the first low-carb book was published in 1863, followed by the first Atkins book which was published in 1972. Additionally, the ketogenic diet is an old diet that has been used to treat difficult-to control seizures in children; originally designed in 1921 to treat epilepsy. The keto diet continued to be administered widely for pediatric patients until the advent of anti-seizure pharmaceuticals.


More recently, the diet has been under study as an alternative method for weight loss (Paleo, South Beach and Atkins diets fit into this category). Additionally, it has also been under study for prevention and treatment of neurological disorders, insulin resistance including polycystic ovarian syndrome (PCOS), type 2 diabetes, cancer, epilepsy, Alzheimer’s disease amongst other conditions.


What is a Ketogenic Diet?

Essentially, the ketogenic diet is a high-fat, moderate-protein and very low carb diet. Thus, the ketogenic (keto) diet, is also commonly referred to as the low-carbohydrate high-fat. Basically, it involves drastically reducing one’s carbohydrate intake and replacing it with fat: carb intake is kept to between five and ten percent of dietary calories, with the balance consisting of relatively high fat and moderate protein intake. The source of this fat and protein may vary widely, from plant-based to primarily animal derived. The reduction in carbs puts one’s body into a state of ketosis – where ketones created in the liver help break down fat for energy.


Tanya Zuckerbrot, MS, RD, a NYC-based registered dietician, bestselling author, and the founder of The F-Factor Diet, explains, “typically we get our energy through a process called glycolysis, which is how carbohydrates are broken down into glucose for energy. In glycolysis, there are higher levels of insulin that promote storage of body fat and block release of fat from adipose tissue, whereas in ketosis, fat reserves are released and broken down, so you don’t store them on the body, but use them.”


The key to this diet is to rely on fat as a source of 60-70% of one’s consumed calories, with 15% calories derived from protein and 10-15% derived from complex carbohydrates. Carbohydrates from all sources should not exceed 30-50 grams/day – not an easy task considering one ripe banana contains 18 grams of carbohydrates. Therefore, many people find this diet so appealing where, in principle, the body switches from using glucose (from carbohydrates) to fat as fuel.


It is known that food consists of three macro-nutrients: carbohydrates, proteins and fats. An essential macro-nutrient is basically a substance the body cannot produce on its own and equally cannot survive without it. The body contains various nutrients including essential fatty acids, essential amino acids but does not contain essential carbohydrates.

However, recent studies have shown that humans can survive with zero carbohydrates and in this context, some of the reasons why carbs are not essential include:

  1. Protein and fat can also provide glucose. A healthy human body can reform the amino acids from protein into glucose.

  2. Carbohydrate deficiency doesn’t result in illness. Deficiencies in protein, essential fats (linolenic acid and linoleic), vitamins and minerals on the other hand can…

  3. Carbohydrates can be used for energy, but they don’t have to be used for energy.

  4. Obviously, our diet should contain some carbohydrates, as we should get the benefit and the pleasure of eating greens and beans. However, in order to get the ketosis nirvana, we should limit the source of carbohydrates to greens and avoid other foods like potatoes, corn, sweet peas, peanuts and limit the beans.


What is Ketosis?

Once you’ve limited yourself to a daily intake of 20 to 50 grams of carbs, it will take few days to reach ketosis. Ketosis refers to a natural metabolic state, where the body produces ketone bodies out of fat, and use them for energy instead of carbs. It occurs when the body has limited access to glucose (blood sugar). Keep in mind that eating too much protein can interfere with ketosis. In order to achieve ketosis, one must remove certain items from one’s diet:

  • Sugary foods: Soda, fruit juice, smoothies, cake, ice cream, candy, etc.

  • Grains or starches: Wheat-based products, rice, pasta, cereal, etc.

  • Fruit: All fruit, except small portions of berries like strawberries.

  • Beans or legumes: Peas, kidney beans, lentils, chickpeas, etc.

  • Root vegetables: Potatoes, sweet potatoes, carrots, parsnips, etc.

  • Low-fat or diet products: These are highly processed and often high in carbs.

  • Some condiments and sauces: These often contain sugar and unhealthy fat.

  • Unhealthy fats: Limit your intake of processed vegetable oils, mayonnaise, etc.

  • Alcohol: Due to their carb content.

  • Sugar-free diet foods: These are often high in sugar alcohols, which can affect ketone levels. These foods also tend to be processed.

The biological rationale for ketogenic diets being used as therapeutic treatments stems from the fact that in this diet one decreases their carbohydrate intake, which will result in low levels of blood glucose causing the body to release less insulin and more fatty acids. Some of these fatty acids are transferred to the liver, where they are oxidized and turned to ketones for energy. During ketogenesis, not only are insulin and glucose levels reduced, but other hormonal changes may occur which may positively impact one’s physiology.

Glucose is the preferred fuel for the brain; however, Ketones can supply energy for the brain; a large portion of the brain can use ketones for energy when the body is low on carbs. In addition, the body can use protein to produce glucose, and this process is called gluconeogenesis. It is alleged that ketosis and gluconeogenesis can fulfill some of the brain’s energy needs.


Keto Diet, Obesity and Diabetes

Research into the ketogenic diet and obesity began in the mid 1960’s, and early results were mixed. More recent research has consistently found that low-carbohydrate diets (both ketogenic and non) lead to greater weight loss than other food plans, including low fat diets.


Ketogenic diets may also improve blood lipids, although the data here are mixed. Other studies have found that keto diets may improve lipoprotein profiles, including several that have found significant decreases in triglycerides and increases in HDL cholesterol. Some studies have found that a ketogenic diet may allow one to lower their use of diabetes medications or may even functionally reverse their diabetes diagnosis.


Studies conducted on obese and diabetic populations following a ketogenic diet resulted in improved glucose markers, decreased blood glucose levels, weight loss, retention in lean muscle mass, and improvements in at least some blood lipids. Ketogenic diets may have also been found to be linked to improvement in their metabolism. Additionally, studies have found that the basal metabolic rate (BMR – the amount of calories the body burns at rest), does not decrease on a keto diet but may drop by as much as 400 kcal/day on a low-fat diet when compared to a very low-carb diet.


Another food plan that relies on ketosis is intermittent fasting, in which a patient will fast for one or more days a week or every day by prolonging the overnight fast. The idea here is that the body will enter ketosis temporarily. Intermittent fasting has been shown, in some cases, to help with the reduction in body fat mass and improvement in metabolic parameters among patients with obesity and type 2 diabetes.

Foods to Eat on a Ketogenic Diet:

  • Meat: red meat, steak, sausage, chicken, turkey.

  • Fatty fish: such as salmon, trout, tuna and mackerel.

  • Eggs: Look for pastured or omega-3 whole eggs.

  • Butter and cream: Look for grass-fed when possible.

  • Cheese: Unprocessed cheese (cheddar, goat, cream, blue or mozzarella)

  • Nuts and seeds: Almonds, walnuts, flax seeds, pumpkin seeds, chia seeds, etc.

  • Healthy oils: Primarily extra virgin olive oil, coconut oil and avocado oil.

  • Avocados: Whole avocadoes or freshly made guacamole.

  • Low-carb veggies: Most green veggies, tomatoes, onions, peppers, etc.

  • Condiments: You can use salt, pepper and various healthy herbs and spices.

A Sample of a Keto Diet:

  • Breakfast: Omelet with avocado, salsa, peppers, onion and spices

  • Lunch: A handful of nuts and celery sticks with guacamole and salsa

  • Dinner: Chicken stuffed with pesto and cream cheese, along with vegetables

Healthy Keto Snacks:

Cheese, a handful of nuts, olives, 90% dark chocolate, a low-carb milkshake with almond milk cocoa butter and nut butter, full-fat yogurt with nut butter and cocoa powder, strawberries and cream and celery with guacamole.


Concerns About Keto:

There are still enough potential concerns about the diet. One’s body stores some of the carbs in the muscle and the liver, and stored glycogen binds with water. Therefore, when one cuts carbs, the glycogen stores go down and one ends up losing a lot of water. Additionally, low-carb diets lead to drastically reduced insulin levels, causing the kidneys to shed sodium and water. For these reasons, low-carb diets lead to a substantial and almost immediate shedding of water weight. Restricting carbs also improves insulin sensitivity and can help decrease inflammation, meaning that circulating hormones are less likely to promote fat storage.


One may go through adjustment period. As the body switches from one energy source to another, another potential issue with ketosis is the “keto flu” that may occur during the early days of the diet. Some potential side-effects include headaches, fatigue, constipation and high cholesterol levels. One may feel weak with poor mental function, increased hunger, sleep issues, nausea, decreased exercise performance and experience GI disturbance. Additional risks are liver problems – with so much fat to metabolize; kidney problems – recommended intake for protein averages 46 grams per day for women and 56 grams for men; constipation – being low in fibrous foods like grains and legumes; fuzzy thinking and mood swings – the brain needs sugar from healthy carbohydrates to function. These may last a few weeks but will subside once the body has adjusted.


As with any dietary plan, there is an opportunity cost; by choosing to eat some things and avoid others, one is missing out on potential nutritive value of many foods that are not consumed. Not eating fruits, legumes, and high-fiber whole grains may be eliminating sources of many beneficial nutrients, including selenium, magnesium, phosphorus and vitamins B and C. There is considerable variation in the macronutrient distribution that forms the balance of the diet, which lacks in the keto diet. The body can subsist without carbs – it won’t just suddenly shut down on you – but it certainly won’t be in top form: missing out on the nutrients from fruits and vegetables could however lead to more inflammation. As you remove carbohydrates from the diet, you’re also removing a lot of fiber, which may lead to constipation. At the same time, eating more fat than you’re used to may lead to diarrhea. Again, these feelings may subside.


With regards to athletes, their requirements for carbs depend on the type of sport they do. For activities such as sprinting or weightlifting (which need short bursts of energy), carbs are a better source of energy than protein or fats because they’re stored in the muscles and are more readily available. For a sustained exercise like long runs, healthy fats are an ideal source because it’s more slow burning.


A ketogenic diet could be an interesting alternative to treat certain conditions and may accelerate weight loss. On the other hand, it is a difficult diet to follow thoroughly and can be somehow heavy on red meat and other fatty, processed, and salty foods. Close monitoring needs to be done to renal function and uric acid on a ketogenic diet. Additionally, in order to determine if one is in nutritional ketosis, monitoring needs to be conducted. While blood testing is the most accurate, non-invasive methods are also available such as breath testing.


One last concern is duration. Generally, ketogenic diets are not followed indefinitely, and no studies have been done on the safety of long-term, uninterrupted ketogenic diets. It is usually recommended to follow a ketogenic diet for a minimum of two or three weeks and maximum up to six to twelve months.


Although some people may thrive on keto, it will be particularly hard for people who avoid animal-based foods. At GTRANCE we recognize the unique genetic and environmental history of each person. It is important to remember that “yo-yo diets” that lead to rapid weight loss fluctuation are associated with higher problems. Therefore, we like to tailor our recommendations to fit the client and we continuously assess whether it is working congruously. The popular approach at GTRANCE is bio-individuality – we don’t believe in any “one size fits all” diets – we rather implement scientific weight loss management approaches without intentional calorie restriction, and we monitor what works for our clients.


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