The Pros and Cons of a Low-Carb High-Fat Diet

The ketogenic diet is being hailed as a way of eating for sustainable weight loss and improvements in physical and mental health. Research shows the low-carb high-fat diet may also be beneficial to patients with diabetes, cancer, and Alzheimer’s disease [1, 8, 9].

But it has its share of critics as well. The keto diet is sometimes referred to as “the bacon and butter diet” because it calls for 75% of daily calories to come from fat. 

So what are the pros and cons of the keto diet?

How the Ketogenic Diet Works

For the pros and cons of keto to make sense, you need to understand what it is.

The ketogenic diet was initially developed as a therapeutic way to treat seizures in patients with epilepsy. It’s now viewed as a natural way of eating that can be beneficial beyond just those who suffer from seizures. 

The diet is made up of roughly: 

  • 75% fat
  • 20% protein
  • 5% carbohydrates. 

This combination enables your body to enter a state of ketosis, where the body switches from burning carbs for fuel to burning fat. 

Fat, protein, and carbohydrates are called macronutrients – “macros” for short. To achieve a keto macro breakdown of 75% fat, 20% protein, and 5% carbs, you first need to know that:

  • One gram of fat contains 9 calories
  • One gram of protein contains 4 calories, and
  • One gram of carbohydrate contains 4 calories.

If you’re eating 2,000 calories a day, that means you should be eating 167 grams of fat, 100 grams of protein, and 25 grams of carbohydrates. Here’s how to calculate how much to consume of each macronutrient:


  • 2,000 calories x 75% fat = 1,500 calories 
  • 1,500 calories / 9 calories per gram = 167 grams of fat


  • 2,000 calories x 20% protein = 400 calories
  • 400 calories / 4 calories per gram = 100 grams of protein


  • 2,000 calories x 5% carbohydrate = 100 calories
  • 100 calories / 4 calories per gram = 25 grams of carbohydrates

Cutting carbs and increasing healthy fat intake will help your body transition to a state of ketosis. This is the physical state where your body is producing ketones for energy and burning fat for fuel. A state of ketosis can support weight loss and is why so many people turn to the ketogenic diet to lose weight.

Getting into ketosis is a critical component of the ketogenic diet. 

You can achieve ketosis by fasting, cutting carbs drastically (typically under 50 grams a day), and/or taking keto supplements, such as BHB (exogenous ketones) and MCT-based meal replacement shakes. 

After becoming fat-adapted, incorporating intermittent fasting (IF) can help boost weight loss or break weight loss plateaus. The most common method of intermittent fasting is 16:8. This is when you go 16 hours without eating and consume all of your calories during an 8-hour eating window.

To find out whether you have achieved ketosis, you can test your blood or urine for the presence of ketone bodies. Depending on your: 

  • Diet
  • Activity level
  • Body type
  • Metabolic state
  • Genetics 

It can take a couple of days to a couple of weeks to reach ketosis. Testing for ketosis is a personal preference. For some, it’s an added inconvenience; for others, it provides added incentive to stay on track.

The Pros of the Ketogenic Diet

The ketogenic diet is associated with many benefits, with weight loss being the most common. 

#1: Supports Weight Loss

When your body enters ketosis, it goes into fat-burning mode, which supports fat loss. Cutting carbs also causes your body to retain less water, which can lead to weight loss [2, 4, 6, 7, 9]. 

The ketogenic diet supports fat loss for a few other reasons as well. Because carbs have fewer calories and digest quickly, they aren’t very satisfying. That means that while you may feel full right after eating carbs, you’ll feel hungry again in a shorter period of time than you would with fats or proteins.

Fat is very satiating, and it’s also rich. When people switch to a low-carb diet and replace the carbs with fats, they mostly find that they can’t eat nearly as much as they could with carbs, which means a decrease in caloric intake and ultimately fat loss.

Finally, keto-ers love supplementing their ketogenic diets with MCT oil, as it’s regarded as the ultimate ketogenic fat source. Research suggests that those who consume MCT oil (or other supplements that contain MCTs) in conjunction with a ketogenic diet saw greater weight loss results than those who did not [1].

#2: Suppresses Appetite and Enhances Satiety

The high amount of fats in the keto diet minimizes carb cravings, provides steady energy for hours, and suppresses appetite [2, 6].

This is true for most people and regarded as one of the best things about the keto diet.

Besides the obvious health benefits to not being hungry all the time, a huge plus is that you spend less time preparing and thinking about food, which frees up your time for more important things.

#3: May Lower Cholesterol

Studies show the keto diet can improve “good” cholesterol (HDL) and lower “bad” cholesterol (LDL). Eating fat increases blood levels of HDL. The higher your levels of HDL, the lower your risk of heart disease.

Eating low-carb can also change your LDL cholesterol, altering it from “bad” to “benign” cholesterol. It does this by turning LDL particles from small (high risk of heart disease) to large (low risk of heart disease) while also decreasing the number of LDL particles in the bloodstream [2, 3, 6, 9, 10, 11].

#4: May Reduce Risk for Heart Disease

Fat used to get a bad rap for not being heart healthy. And (crazily enough), carbs and grains were seen as positive for heart health.

We now know better, and research shows that reducing carb intake can lower blood triglycerides, which are fat molecules in the blood. High levels of blood triglycerides can put you at higher risk for heart disease [3, 4, 6, 7, 9].

#5: May Lower Blood Pressure

Research shows eating a low-carb diet can have positive impacts on blood pressure. Hypertension is a risk factor for many diseases, including heart disease, stroke, and kidney failure [4, 6, 7, 9].

#6: Reduces Insulin Levels and Insulin Resistance

Studies show the keto diet can reduce blood sugar and insulin fluctuations due to reduced carbohydrate consumption.

Better insulin control can also help improve the associated metabolic disorders and symptoms linked to high insulin and blood sugar [2, 4, 9].

#7: Improves Cognitive Function

One of the best benefits of a ketogenic diet is the improvement in cognitive function. Fat is converted into ketones in your liver and then sent to the brain. Ketone bodies (also called ketones) are able to cross that blood-brain barrier, so can be used as energy by your brain cells.

The keto diet has been used for decades to treat epilepsy in children, and it is currently being studied for its potential beneficial impacts on other neurological diseases, such as Alzheimer’s and Parkinson’s [1, 12] because of this.

#8: Enhances Mood and Improves Sleep Quality

Many ketogenic dieters find that when their body has entered ketosis, they need less sleep to feel as alert, energetic, and healthy as they previously did on the same amount.

Because your hormones aren’t following the insulin spikes and crashes that are typical of the Standard American Diet (SAD), most ketogenic dieters report feeling more stable and level, and being in a better mood [12, 13].

#9: Boosts Energy Levels

The sluggishness and lethargy you feel after a heavy carb-filled meal happens because of that insulin spike and reactive sharp drop in blood sugars. 

Eating a high-fat diet provides steady energy and helps you avoid crashes that are associated with eating a high-carb diet. 

Since ketones are the brain’s preferred source of energy, a ketogenic diet leaves you feeling more alert and mentally energized without having to supply a steady stream of calories [13].

#10: Supports Regulated Hormones

One of the top reported reasons for women wanting to try the ketogenic diet besides weight loss is for hormonal balance.

Women who suffer from hormone imbalance may find relief with the ketogenic way of eating. For example, research supports that keto may help with: 

  • Polycystic Ovarian Syndrome (PCOS) and related infertility. By avoiding insulin spikes while following a ketogenic lifestyle, women with PCOS report a reversal of increased androgen hormones, specifically testosterone, which leads to a reduction in PCOS symptoms and increased fertility [14]. 
  • Thyroid health and longevity. Along with balancing sex hormones, a ketogenic lifestyle has a positive effect on thyroid hormones as well. A very low-carb diet tends to drive down T3, the main active thyroid hormone. Higher T3 levels make your cells use more energy (hyperthyroidism), which can increase free-radical production. Many scientists believe that lower levels of T3 actually increase lifespan by conserving energy and decreasing free-radical production. A ketogenic lifestyle is positively correlated with improved thyroid health and overall longevity [15]. 

The Cons of the Ketogenic Diet

There are many advantages of keto, but you also have to consider the downside.

#1: Requires an Adaptation Process

Getting keto adapted can take one to two weeks and the transition can be uncomfortable for some people.

The “keto flu” is commonly used to describe flu-like symptoms associated with the transition process:

  • headaches
  • fatigue
  • nausea
  • muscle aches etc.

Due to restricted carbohydrate intake, your body is not retaining as much water so loss of electrolytes is common. This can easily be rectified with taking mineral supplements or exogenous ketones, such as beta-hydroxybutyrate [16].

#2: Keto May Cause Irregularity

Dramatically increasing your fat intake while drastically cutting your carb intake may cause gastrointestinal issues, ranging from constipation to diarrhea. 

This is something that should resolve itself when your body gets fat-adapted [5]. There is also the potential for nausea, particularly when switching from a low-fat diet to the ketogenic diet. It can take a while for the gall bladder, pancreas, and liver to adapt to digesting high amounts of fat [17]. 

#3: Restricts Certain Foods

Some people simply don’t like banning entire food groups, and the keto diet requires you to give up all forms of sugar (no more candy, ice cream, or donuts), and popular carbs such as bread, rice, and pasta. 

Keto also limits most fruits due to the fructose content, as well as starchy vegetables, such as potatoes and corn. The good news is that as your body becomes keto-adapted, your sugar cravings will dramatically fall or disappear altogether. 

#4: May Cause High Cholesterol for Certain People

While most people will see their cholesterol fall along with their weight, there are some that may see the opposite due to the meat-heavy nature of the diet. This is typically a genetic predisposition and means the keto diet is not right for everyone [11].

#5: Makes Social Gatherings Harder

Dining out at restaurants will require more planning and research due to hidden carbs on restaurant menus. Attending birthday parties, weddings, and other social events will require more self-discipline. 

If you want to drink alcohol, you’ll have to limit yourself to one or two low-carb drinks. This means dry wines (the dryer the better!) and unflavored clear liquors, such as vodka, gin, and tequila. 

There are a surprising number of keto-friendly alcoholic beverages that won’t knock you out of ketosis. For dessert, dark chocolate (at least 70% cocoa) is okay in moderate amounts. Stick to keto-friendly chocolates that are naturally sweetened with zero-calorie sweeteners, such as stevia and erythritol. You can have sugar-free candies on occasion, just be aware that the sugar alcohols may cause digestive discomfort if you have too much.

Decide Whether the Ketogenic Diet is Right For You

Now that you have a better understanding of the pros and cons of keto, here are a few other resources that can help you make a decision about whether this way of eating is right for you.

When starting a new diet, consult your doctor prior to making any significant changes, especially if you take any prescription medication.

Keto Resources

Ten Tips for Doing Keto the Right Way: Thinking about giving the ketogenic diet a try? People are using it not only to lose weight, but to feel more energized, sleep better, and improve their mental focus. It’s not hype. The keto diet is a top health trend because it works. But before you go all in, here are some tips for doing keto successfully.

Keto Recipes: We’ve developed each recipe to help you enjoy a keto lifestyle. Many of our recipes also fit perfectly into most Paleo and other low-carb/high-fat (LCHF) diets. Use them to help lose weight, maintain your form, feel more energetic, and supercharge your body and your brain.

Keto Meals: Starting a new diet can be challenging so make it easier by ordering pre-cooked ketogenic meals that can be heated up in minutes at work or at home. They’re made with natural, whole-food ingredients, flash frozen to retain nutrients and ensure maximum freshness, and delivered straight to your door. Our meals are designed to simplify meal planning, help you lose weight, and support ketosis.


  1. Neuroprotective and disease-modifying effects of the ketogenic diet
  2. A Low-Carbohydrate as Compared with a Low-Fat Diet in Severe Obesity
  3. Treatment of diabetes and diabetic complications with a ketogenic diet.
  4. Effects of Ketogenic Diets on Cardiovascular Risk Factors: Evidence from Animal and Human Studies.
  6. The National Cholesterol Education Program Diet vs a Diet Lower in Carbohydrates and Higher in Protein and Monounsaturated Fat
  7. A randomized trial of a low-carbohydrate diet for obesity.
  8. Mitochondria: The ketogenic diet–A metabolism-based therapy.
  9. Comparison of the Atkins, Zone, Ornish, and LEARN diets for change in weight and related risk factors among overweight premenopausal women: the A TO Z Weight Loss Study: a randomized trial.
  10. Low density lipoprotein particle size and coronary artery disease.
  11. Carbohydrate Restriction Alters Lipoprotein Metabolism by Modifying VLDL, LDL, and HDL Subfraction Distribution and Size in Overweight Men
  12. Impact of dietary fats on brain functions.
  13. Ketogenic diet benefits body composition and well-being but not performance in a pilot case study of New Zealand endurance athletes.
  16. A review of the carbohydrate-insulin model of obesity.
  17. Khodarahmi M, Azadbakht L. Dietary fat intake and functional dyspepsia. Adv Biomed Res. 2016 Apr 21;5:76.

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