What is the Keto Diet and How Does It Work?

The keto diet has become an incredibly popular way to lose weight and improve health in recent years. But what exactly is the keto diet, and how does it work to provide these benefits? This article will explore the science and practice behind the ketogenic diet.

What is the Keto Diet?

What is the Keto Diet and How Does It Work?
What is the Keto Diet and How Does It Work?

The keto diet is a very low-carb, high-fat diet that shares similarities with paleo, Atkins, and other low-carb diets. The goal is to put the body in a metabolic state called ketosis.

Here's a quick rundown of how the keto diet works:

  1. You severely restrict carbohydrate intake to about 5-10% of total calories. This drives down insulin levels and blood sugar.
  2. With very low carb intake, the body starts burning its glycogen stores for energy. 
  3. Glycogen is essentially stored carbohydrate.Once glycogen is depleted, the body switches to running almost entirely on fat. 
  4. This metabolic state is called ketosis.Ketones are produced as a byproduct of burning fat.
  5.  Ketones are used as an alternative energy source in the absence of carbohydrates.

The “classic” ketogenic diet contains 75% fat, 20% protein and just 5% carbs. Lower-fat versions like the Standard Ketogenic Diet are also popular. But fat still provides the majority of calories.

The keto diet has become incredibly popular over the past decade. Here are some of the main reasons for its popularity:

  • Weight loss: The keto diet can lead to fast weight loss, without having to count calories or restrict portions. Many have success with keto for weight loss.
  • Blood sugar control: Because carb intake is limited, the diet can dramatically reduce blood sugar and insulin levels. This helps those with prediabetes or type 2 diabetes.
  • Other health benefits: The diet has been shown to reduce risk factors for heart disease, control blood pressure, and may benefit a number of brain disorders.

The ketogenic diet also eliminates hunger and cravings in many people, due to stable blood sugar and appetite-regulating hormones. It may be one of the easiest diets to stick to for these reasons.

What Are the Benefits of a Keto Diet?

What is the Keto Diet and How Does It Work?
What Are the Benefits of a Keto Diet?

Here are some of the top evidence-based health benefits of the ketogenic diet:

Weight Loss

The keto diet promotes weight loss in several ways:

  • Lower insulin levels and stable blood sugar reduce cravings and hunger. This usually leads to eating fewer calories without having to think about it.
  • The high fat intake is satisfying and curbs appetite. Ketosis suppresses ghrelin, the “hunger hormone.”
  • Water loss in the first week accounts for quick weight loss on keto. Each gram of glycogen is bound to 3-4 grams of water. As glycogen is depleted, water is lost.
  • The keto diet may boost calorie burning a bit, including calories burned by the brain. It takes a lot of energy for the body to run on ketones!

For all these reasons, studies show low-carb and keto diets result in more weight loss compared to low-fat diets. They also improve many weight-related disease markers.

Blood Sugar Control

Because carbohydrate intake is limited to 20-50 grams per day on keto, the diet dramatically lowers blood sugar and insulin levels.

This is good news for those with high blood sugar or insulin resistance issues like prediabetes and type 2 diabetes. Low-carb diets like keto can reduce or even reverse type 2 diabetes in many cases.

Some diabetes medications also become unnecessary on keto due to normal blood sugar levels.

Improved Heart Disease Risk Factors

Heart disease is the #1 cause of death worldwide. The keto diet appears to significantly improve a number of risk factors for heart disease:

  • Lowers triglycerides and “bad” LDL cholesterol levels
  • Raises “good” HDL cholesterol
  • Reduces blood pressure
  • Improves arterial function and other markers

For these reasons, the keto diet may lower the risk of heart disease long-term. But more studies are needed.

Other Health Benefits

The keto diet appears to offer other health benefits as well:

  • Protects brain function: The keto diet can reduce symptoms of Alzheimer's, Parkinson's, and epilepsy. Some research shows improved mental performance in ketosis.
  • May help polycystic ovary syndrome (PCOS): Low-carb diets are linked to improved hormone balance and fertility in PCOS.
  • Benefits certain cancers: Ketosis starved cancer cells of energy and could enhance the effects of chemotherapy. It's being used successfully alongside cancer treatment.
  • Reduces acne: Lower insulin levels and eating less sugar or processed foods may reduce acne.

It's important to note these areas need more research to fully understand the effects. But there are promising health benefits outside of weight loss.

What Are the Risks of a Ketogenic Diet?

What is the Keto Diet and How Does It Work?
What Are the Risks of a Ketogenic Diet?

The keto diet is safe for most people, but does come with some risks to be aware of.

Potential keto diet dangers include:

The “Keto Flu”

Carb withdrawal can cause temporary side effects in the first few weeks. Symptoms may include headaches, fatigue, dizziness, insomnia, nausea, and constipation. This is sometimes called the “keto flu.”

It’s caused by sudden loss of water and electrolytes as glycogen stores are depleted. Drinking plenty of water and getting enough sodium, magnesium and potassium minimizes symptoms.

Hypoglycemia in Diabetics

People on diabetes medication could experience hypoglycemia (low blood sugar) on keto due to reduced medication needs. Blood sugar monitoring is important to avoid this.

Digestive Issues

A low-carb diet with more fat can be hard on some people’s digestive system. Diarrhea or constipation are possible side effects. This may subside with adaptation to the diet.

Nutrient Deficiencies

The keto diet eliminates many foods, so it’s important to eat a variety of healthy keto-friendly foods and supplement if needed. Nutrients of concern include B vitamins, calcium, iron and omega-3 fats.

High LDL Cholesterol

Keto naturally raises LDL “bad” cholesterol in some people. But studies show particle size improves on keto – from small and dense to large and fluffy – which reduces cardiovascular disease risk.

Kidney Stones

Kidney stones or kidney damage are a concern on very low-carb, high-protein diets. Drinking enough fluids and eating fiber from non-starchy vegetables minimizes this risk.

Not a Long-Term Solution

Keto was originally designed as a medical diet to treat seizures, not as a long-term eating solution. The impact of years-long ketosis is unknown, so it’s smart to have “breaks” now and then.

Not Suitable for Everyone

The keto diet should be approached with caution in certain populations, like those with thyroid issues, gallbladder disease or a history of disordered eating. Strict keto isn’t recommended during pregnancy or breastfeeding either.

While the keto diet is safe for most people, there are circumstances where caution is warranted. As with any diet, it’s important to discuss things with your doctor.

How Does the Keto Diet Work to Burn Fat?

What is the Keto Diet and How Does It Work?
How Does the Keto Diet Work to Burn Fat?

So how does eating a high-fat, low-carb diet force the body to run on fat for fuel? Here’s a simplified breakdown of what happens in the body on keto:

  1. Carb restriction to 20-50g per day or less. This lowers insulin and blood sugar levels.
  2. Glycogen stores are fully depleted after a few days of keto. This is the body’s storage form of carbohydrate from the liver and muscles.
  3. Fat burning increases as the body's main fuel source. Ketones are produced from fat breakdown.
  4. Ketones rise in the bloodstream. Ketone bodies, including acetoacetate, beta-hydroxybutyrate and acetone, are produced by the liver as alternative fuels on a ketogenic diet.
  5. Body switches to running on fat. Once ketosis kicks in and ketone levels rise, you're effectively running on fat. Body fat, dietary fat, and ketones fuel most cells.
  6. Appetite regulation occurs as hunger and cravings decrease due to ketone bodies suppressing appetite.
  7. Weight loss occurs based on a stable metabolic state where fat stores are released and burned for energy.

In a nutshell, the keto diet works by shifting the body's main fuel source from carbs to fat, resulting in weight loss and other health benefits. Let’s look deeper at how ketosis works.

What is Ketosis and Why Does it Burn Fat?

What is the Keto Diet and How Does It Work?
What is Ketosis and Why Does it Burn Fat?

Ketosis is a normal metabolic process where the body breaks down fat into compounds called ketones. They are used for energy in the absence of adequate carbohydrates.

To induce ketosis on keto, carb intake is kept very low – usually under 50 grams per day. This depletes the glycogen (stored carbs) in the liver and muscles.

The body responds by breaking down fats into ketones to supply energy to the brain and other cells that can’t directly run on fat. This keeps critical body functions working when carbs are lacking.

Ketosis suppresses appetite, leading to calorie restriction that results in additional weight loss beyond what could be achieved on a standard low-calorie diet.

Weight loss stalls on most diets because the body fights back against calorie restriction. Ketosis takes advantage of a natural physiology that allows the body to tap into fat stores for energy. This is why ketogenic diets result in faster and more sustainable weight loss without hunger or deprivation.

What Are the Different Types of Keto Diets?

What is the Keto Diet and How Does It Work?
How Does the Keto Diet Promote Weight Loss?

There are several versions of keto eating. Here are four of the most common ketogenic diet variations:

Standard Ketogenic Diet (SKD) – This is the classic keto diet plan. It contains 75% fat, 20% protein and just 5% carbs. The majority of calories come from fat.

Cyclical Ketogenic Diet (CKD) – This diet involves periods of higher carb eating for 1-2 days, followed by 4-6 days of keto. Athletes use this version.

Targeted Ketogenic Diet (TKD) – Allows eating carbs strategically around workouts. Carbs are restricted the rest of the day to remain in ketosis.

High-Protein Ketogenic Diet – This keto variation increases protein intake and reduces fat. Protein is often around 35% of calories with 60% fat and 5% carbs.

Standard keto is the most researched and recommended, but each variation has different benefits. Higher protein keto or cyclical keto can suit some goals like building muscle or boosting athletic performance.

How Does the Keto Diet Promote Weight Loss?

What is the Keto Diet and How Does It Work?
How Does the Keto Diet Promote Weight Loss?

Here are the main reasons keto causes significant weight loss:

Appetite Regulation

Eating less happens effortlessly due to reduced hunger and cravings. Ketones suppress the “hunger hormone” ghrelin. Fat and protein stimulate cholecystokinin (CCK) which increases satiety.

Water Loss

Each gram of glycogen in the body is bound to 3-4 grams of water. As glycogen is depleted in the first week of keto, excess water is shed resulting in rapid weight loss.

Increased Fat Burning

Ketosis allows you to burn fat directly for energy. And keto may slightly boost your metabolic rate and total calories burned. Various tissues like the brain run more efficiently on ketones than glucose.

Muscle Sparing

Keto diets help preserve lean body mass. The high protein intake and stimulation of IGF-1 helps retain muscle, even while shrinking fat stores.

Reduced Fat Storage

Insulin drives fat storage. Ketosis lowers insulin levels which causes fat to be pulled from storage and moved into the bloodstream to provide energy.

How Does the Keto Diet Affect Blood Sugar Control and Insulin?

What is the Keto Diet and How Does It Work?
How Does the Keto Diet Affect Blood Sugar Control and Insulin?

By keeping carb intake very low, the keto diet significantly lowers blood sugar and insulin levels.

Blood sugar is kept stable because dietary carbohydrates are severely restricted and can't spike blood sugar. Protein and fat have minimal effects on blood glucose.

Insulin decreases dramatically – often to a quarter or third of previous levels within days of starting keto. Insulin is the hormone that tells our body to store fat, so this allows fast access to fat stores and leads to weight loss.

Lower insulin levels and stable blood sugar provide huge benefits to those with high blood sugar, insulin resistance, metabolic syndrome, prediabetes or type 2 diabetes.

What Does the Science Say About Keto and Weight Loss?

What is the Keto Diet and How Does It Work?
What Does the Science Say About Keto and Weight Loss?

Dozens of randomized controlled trials have compared low-carb and ketogenic diets to low-fat diets for weight loss. The research shows:

Keto causes more weight loss – Low-carb diets lead to significantly more weight loss compared to low-fat diets, even with equal calories. The mechanisms described above lead to effortless weight loss.
More belly fat loss – Keto results in ~2 to 3 times greater loss of the dangerous visceral belly fat compared to low-fat diets.
Greater fat mass loss – There is much greater loss of body fat while maintaining lean mass and muscle. A meta-analysis found individuals lost 4 more pounds of body fat on low-carb diets.
Improved satiety – Keto diets reduce hunger and bring about spontaneous calorie reduction without counting calories or portion control.
Better retention – There is less weight regain on low-carb diets over 1-2 years compared to low-fat.

According to the science, the keto diet provides impressive weight loss results. Keto is one of the most effective ways to burn fat while maintaining muscle mass and curbing appetite.

What Are Some Keto Diet Meal Plans and Recipes?

What is the Keto Diet and How Does It Work?
What Are Some Keto Diet Meal Plans and Recipes?

Here is a sample one day keto meal plan to provide an idea of what types of foods and meals you can enjoy:

Breakfast: Fried eggs with avocado and spinach

Lunch: Bunless burger (beef patty and cheddar) served with pickles, mustard, and a salad

Snack: Celery sticks topped with cream cheese

Dinner: Grilled chicken thighs with broccoli topped in olive oil

Dessert: Mixed berries topped with heavy cream

There are endless combinations of delicious and satisfying keto meals. Popular keto diet recipes include:

  • Fajita bowls with chicken, veggies, guacamole, salsa and cauliflower rice
  • Chicken Alfredo made with zucchini noodles instead of pasta
  • Green smoothies made with avocado, leafy greens, almond milk and collagen powder
  • Bacon artichoke dip served with vegetables or pork rinds
  • Fathead pizza crust made with mozzarella, egg and almond flour
  • Chocolate avocado mousse sweetened with stevia or monk fruit

The keto diet opens up many opportunities for high-fat, low-carb recipes and meal plans. There are now tons of keto cookbooks and online resources for keto meal ideas.

What Are Some Tips and Tricks for Starting and Maintaining Ketosis?

What is the Keto Diet and How Does It Work?
What Are Some Tips and Tricks for Starting and Maintaining Ketosis?

Here are some helpful tips for getting started with the ketogenic diet:

Ease into it – Start by reducing carbs to 100g/day for the first week. Slowly decrease to 50g/day and then 20-30g/day over a few weeks. This minimizes side effects.

Remove high-carb foods – Throw out all sweets, grains, starches, sodas, juices, and processed carbs from your kitchen. Stock up on meats, eggs, oils, low-carb veggies, herbs and spices.

Plan your meals – Make a weekly meal plan focused around protein with veggies and healthy fats. Planning helps you stay on track.

Drink plenty of water – Shoot for at least 2-3 liters per day to stay hydrated and prevent constipation. Add electrolytes to prevent headaches and fatigue.

Supplement if needed – Magnesium, B vitamins, fiber and omega-3s can help minimize side effects of keto flu, constipation, nutrient deficiencies or high LDL.

Move your body – Incorporate movement like walking, weights, or sprints. This kickstarts ketosis, helps burn more fat, and prevents loss of lean mass.

Test ketones – Use ketone urine strips or a breath meter to ensure you’re in ketosis, especially in the initial stages. Blood meters are the most accurate.

Be patient – It can take a few weeks to become fat adapted. Stick with it and the results are worth it!

With some preparation and patience, anyone can implement a successful keto diet. Stay strict for at least 3-6 months to reap the most benefits.

What Are Some Common Problems with the Keto Diet and How Can You Avoid Them?

Some potential issues that can arise on the keto diet and ways to prevent them include:

Keto flu – Drink 3-4 liters water a day with 5,000 mg sodium, 1,000 mg potassium, and 300 mg magnesium to replace electrolytes. Take it easy while transitioning.

Constipation – Up fiber from veggies, chia seeds, and supplements. Magnesium also helps.

Heart palpitations – Palpitations can happen from electrolyte imbalance. Get enough sodium, potassium and magnesium. Stay hydrated.

Plateaus – Stalls happen due to hidden carbs or eating too much protein. Track diligently and lower protein intake. Consider intermittent fasting.

Increase in LDL cholesterol – Increase healthy fats while lowering saturated fats to improve the LDL particle size and reduce risk.

Trouble staying in ketosis – Avoid “hidden” carbs in things like sauces, dressings, nuts, dairy and sweeteners. Stick to whole, unprocessed foods.

Digestive issues – Try slowly ramping up fats. Consider MCT oil. Add fermented foods for gut health. Magnesium can also help relieve constipation.

Lack of energy – This often resolves in a few weeks as your body adapts. Make sure to get enough calories from fat. Try MCT oil or exogenous ketones.

Hypoglycemia – Those on diabetes meds need to monitor blood sugar closely to avoid lows. Speak to your doctor about adjusting medication.

Nutrient deficiencies – Eat lots of nutrient-dense foods. Take a high-quality multivitamin and supplement key nutrients like magnesium, omega-3s, vitamin D, and B vitamins.

Kidney stones – Drink 3-4 liters of fluid daily and eat foods high in citrate like lemon, limes, tomatoes and peppers to prevent kidney stones.

Weight loss stalls – Stalls are normal, but can sometimes indicate too many carbs or calories. Try intermittent fasting or carb cycling to break a plateau.

Bad breath – This is from ketone production. Drink more water. Use gum, mints or breath sprays. Antibacterial mouthwash can help too.

With some troubleshooting, these common keto problems can be easily fixed. It gets much easier as you become fat adapted.

Is the Keto Diet Safe Long-Term?

What is the Keto Diet and How Does It Work?
Is the Keto Diet Safe Long-Term?

Much remains unknown about long-term effects of ketogenic diets. Possible concerns include:

  • Increased risk of kidney stones – Very low carb diets increase urine calcium and acidity, increasing risk of kidney stones. Staying hydrated and eating adequate fiber reduces this risk.
  • Impacts on bone health – Some experts warn low carb diets increase bone breakdown. But some studies show equal or improved bone density. Ensuring adequate calcium, vitamin D and exercise helps.
  • Gut health – Anecdotal reports indicate potential gut issues, like bacterial overgrowth or stomach discomfort. But research shows mixed evidence. More studies are needed.
  • Sustainability – Very low carb can be hard to stick to forever. Cyclical ketosis with carb refeeds or carb cycling may be more sustainable long-term.
  • Nutrient deficiencies – Some micronutrients like B vitamins and fiber are reduced on keto. However, deficiencies are rare with a well-formulated diet.
  • Higher “bad” LDL cholesterol – LDL rises in about 50% of people on keto. But particle size improves. Additional research is needed on long-term heart impacts.
  • Lack of long-term safety data – The keto diet was designed for medical therapy, but hasn’t been studied for decades as a lifestyle.

The keto diet does appear to be safe for most people short-term. But more research is still needed on long-term effects. Periodic carb cycling can help mitigate concerns.

Who Should Not Follow a Ketogenic Diet?

What is the Keto Diet and How Does It Work?
Who Should Not Follow a Ketogenic Diet?

The keto diet is not suitable for everyone. You should avoid keto if you:

  • Have a history of disordered eating or feel it may trigger unhealthy habits
  • Are pregnant or breastfeeding
  • Have liver or kidney disease
  • Have gastrointestinal issues like small intestinal bacterial overgrowth (SIBO)
  • Have gallbladder issues
  • Have a history of pancreatitis
  • Have type 1 diabetes – keto can be used but requires close medical supervision
  • Have thyroid issues – very low-carb can affect thyroid hormones
  • Take SGLT2 inhibitor diabetes medication – ketoacidosis risk
  • Take blood pressure medication – keto may cause excessively low blood pressure
  • Struggle to eat adequate calories or have nutritional deficiencies
  • Are an elite athlete – some benefit from higher carb intake for performance
  • Are a child or teenager – keto is not recommended for most youth

Of course, consult with your healthcare provider before starting any diet, especially if you have any medical conditions or take medications that could be affected. While keto is safe for most people, there are cases where caution is warranted.

Concluding Thoughts on the Ketogenic Diet and Health

What is the Keto Diet and How Does It Work?

The keto diet is a proven way to lose weight, lower blood sugar, and improve many biomarkers for health. Research to date suggests the diet is generally safe for most populations in the short term, with some caveats.

By severely restricting carbs to induce ketosis, the keto diet allows the body to run on fat for fuel. This taps into fat stores while keeping you satiated. Weight loss becomes effortless compared to low-fat diets.

Beyond weight loss, keto improves insulin resistance, blood glucose control, and reduces heart disease risk factors. Potential benefits have been shown for diabetes, polycystic ovary syndrome (PCOS), cancer, brain disorders, acne and more.

However, the keto diet is not a magic solution. It works best when combined with other healthy habits like eating whole foods, exercising, managing stress and getting enough sleep.

As with any major diet change, it’s wise to discuss things with your medical provider before starting a ketogenic diet, especially if you have any underlying health conditions or take medications.

While the long-term effects still need more research, the evidence is clear that a well-formulated keto or low-carb diet can provide impressive health benefits for many people.


What are the main benefits of the keto diet?

The main benefits of keto are weight loss, lower blood sugar and insulin levels, and improved markers for heart disease. Keto may also benefit brain health and certain disorders like PCOS or acne.

What foods can you eat on the keto diet?

Keto-friendly foods include meat, fish, eggs, full-fat dairy, healthy oils, avocados, nuts and seeds, and low-carb vegetables like leafy greens. Sugary and starchy foods must be avoided.

How much fat should you eat on keto?

Around 70-80% of total calories should come from fat on a standard ketogenic diet. The majority comes from healthy unsaturated fats like olive oil, avocado, nuts, seeds and fatty fish.

How do you know if you’re in ketosis?

Ways to tell if you’re in ketosis include urine ketone strips, breath ketone meters, and blood ketone meters. Symptoms like reduced appetite, quick weight loss, and smelly breath also indicate ketosis.

Is keto safe long-term?

More research is still needed on the long-term impact of ketogenic diets. Periodic carb cycling helps mitigate concerns around kidney stones, nutrient deficiencies, and cardiovascular disease risk.

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