What Is the Keto Diet and Should You Try It?

What separates a fad diet from a legitimate nutritional practice? If you’re trying to lose or gain weight, or make any kind of change to your general health habits, it’s a question you should ask yourself before adjusting how you interact with food. 

Some types of diets ride entirely on hype and lack a substantial, evidence-based foundation. These are the ones you should be wary of. And, generally speaking, the more extreme a diet is, the less legitimacy it has. However, there are certainly exceptions.

The ketogenic diet, or keto diet for short, emphasizes high fat intake while significantly reducing carbohydrates. It was initially developed as a treatment for epilepsy (a seizure disorder) in the 1920’s, but in recent years has received praise for its potential to enhance endurance, preserve muscle mass, and fine-tune body fat levels. Is it just another fad diet, or does the keto diet live up to the hype?

Editor’s Note: The content on BarBend is meant to be informative in nature, but it should not be taken as medical advice. When starting a new training regimen and/or diet, it is always a good idea to consult with a trusted medical professional. We are not a medical resource. The opinions and articles on this site are not intended for use as diagnosis, prevention, and/or treatment of health problems. They are not substitutes for consulting a qualified medical professional.

What Is the Keto Diet?

In the 1920s, the ketogenic diet, or keto diet, was developed as a dietary treatment for epilepsy. While it’s still considered an effective strategy to reduce seizures, the keto diet has gained attention for its potential health, physique, and performance benefits. (1)

The macronutrient split of a keto diet is generally 55 to 65 percent fat, 30-35 percent protein, and only five to 10 percent carbs. What sets keto apart from other low-carbohydrate diets is the daily carbohydrate maximum of 20 to 50 grams per day. The extremely low carb intake leads to rapid weight loss (mostly from body water, initially) and the production of ketones, which are byproducts of fat breakdown. (1)(2) 

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The Keto Diet and Health

In addition to curbing seizure frequency, weight loss studies have shown that the keto diet can improve cardiometabolic health and insulin sensitivity in overweight people, or those suffering from obesity or Type-2 diabetes. There’s also some evidence testosterone can increase after keto diet-induced weight loss. (1)(2)(3)(4)(5)(6)

The Keto Diet and Performance

Athletes who follow a keto diet could also experience fat loss, but the other health benefits are limited for people who are already metabolically healthy, and it doesn’t provide any performance benefits. Contrary to popular belief, though, this low-carb diet doesn’t lead to muscle loss or reduced athletic performance in most cases. It may not be ideal for everyone, but it’s suitable for strength, power, and endurance athletes who prefer a low-carb, high-fat diet. (7)(8)(9)(10)(11)

How Does the Keto Diet Work? 

Normally, most cells in the body will use a combination of carbohydrates and fats for energy depending on several factors, including energy balance, dietary intake, being in a fed or fasting state, and being at rest versus engaging in exercise. (1)(2)

There are some cells that require glucose, though, and the body adapts to maintain a relatively stable concentration of glucose in the blood over time. During times of carbohydrate restriction, the body can release glucose from liver glycogen, but this only lasts a matter of hours. When liver glycogen is depleted, some glucose can be produced through a process called gluconeogenesis, but this isn’t enough to meet the energy demands of every cell. (1)(2) 

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So, after a few days of very low carbohydrate intake, your cells will shift to using fats as their primary energy source and the body will enter a state of “nutritional ketosis.” Ketone bodies, or ketones, are the byproducts of fat metabolism produced during times of carb restriction, but they aren’t just useless leftovers. Ketones provide an additional source of energy. (1)(2) 

In Short: Ketogenic diets involve removing nearly all dietary carbohydrates, which are your body’s “preferred” fuel source. In their absence, your body opts to burn fat for energy instead by converting fat into ketones. 

Keto and Hormones

When blood sugar levels rise after a meal, insulin is released to shuttle carbs and fats into cells where they can be broken down for energy or stored (as glycogen and body fat) for later use. Although insulin levels will still go up after a low-carb meal, those levels tend to be lower on a keto diet compared to a higher-carb diet. (4)(5) 

This explains why people with Type-2 diabetes will often see improvements in markers of insulin sensitivity and glucose regulation on a keto diet. (4)(5) Lower insulin levels do not, however, lead to fat loss or prevent fat gain, despite what some social media influencers might say. (12)

Keto and Fat Loss

It’s important to keep in mind that using dietary fat for energy isn’t the same thing as burning body fat for energy. In other words, following a keto diet won’t automatically result in fat loss. 

The rapid weight loss people experience when starting the diet is actually due to a loss of body water, not body fat. Although a keto diet might lead to small elevations in metabolic rate — which translates to more calories burned each day — the changes are too small to lead to meaningful fat loss. (1)(12)(13)

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The keto diet might be superior to low-fat diets when it comes to the treatment of Type-2 diabetes, and some studies report less hunger on a keto diet. That said, a calorie deficit is still required to lose fat, and most evidence shows that keto diets and low-fat diets are similarly effective (or ineffective) for long-term weight loss goals. (12)(13)(14)(15)

Keto and Seizures

Brain cells can use ketones for energy since they cross the blood-brain barrier, but it’s still unclear how the keto diet works to reduce seizures. Researchers think ketosis could improve mitochondrial function, modify certain neurotransmitters, and lower glucose levels in the brain, which collectively contribute to stabilizing connections between brain cells. Interestingly, the diet is much more effective in adolescents compared to adults. (2)

Benefits of the Keto Diet

When followed prudently, a keto diet can support health and physique goals. Certain groups will benefit more from following a keto diet — including people concerned about their cardiovascular disease risk — but it can also be useful for recreational exercisers and athletes.

Better Body Composition

The keto diet is one way to improve body composition, or the ratio of body fat to muscle mass. A keto diet usually leads to faster weight loss than a low-fat diet for the first one to six months (without sacrificing muscle mass). 

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As long as you maintain an energy surplus, you can use keto for muscle gain when paired with resistance training. It’s similarly effective for athletes, recreational exercisers, and people with overweight, obesity, or Type-2 diabetes. (3)(5)(7)(8)(9)(10)(14)

Better Cardiometabolic Health 

A keto diet could be used to improve cardiometabolic health markers and reduce the risk of heart disease. A large number of studies have reported reductions in cholesterol levels, circulating triglycerides (fats), blood pressure, body weight, body fat, and waist circumference after following a keto diet. 

Some studies have also shown reductions in LDL cholesterol (which is linked to cardiovascular disease) and elevations in HDL cholesterol (which is protective.) (2)(3)(4)(5)

Better Glycemic Control

Compared to other groups, people with prediabetes or Type-2 diabetes are likely to see the most benefits from following a keto diet. In addition to all of the cardiometabolic benefits, a keto diet can also reduce fasting blood sugar and improve markers of insulin sensitivity. These improvements have reportedly been sustained for up to two years in people with Type-2 diabetes. (2)(4)(5)

Fewer Seizures in Adolescents

For reasons that are still unknown, a keto diet can significantly reduce epileptic seizures in adolescents. This is an especially important option for drug-resistant epilepsy. While long-term studies are limited, a strong body of evidence suggests a 50 to 90 percent reduction in seizure frequency while following a keto diet. (2)(16)

Drawbacks of the Keto Diet

Despite its potential health and physique benefits, the keto diet has several limitations. It can be hard to follow long-term, and could be dangerous for certain populations. It’s important to keep these in mind if you’re thinking about starting the diet. 

The Keto Flu

The “keto flu” is one of the most common complaints about starting a keto diet. In the first several days or weeks of the diet, most people will experience side effects like fatigue, headaches, dizziness, nausea, constipation, and even vomiting.

Some people will also notice that their sleep quality and exercise performance suffer. Symptoms subside on their own eventually, but staying hydrated can help ease them in the meantime. (1)

It’s Hard to Sustain

A keto diet is often highly effective for weight loss and subsequent health improvements for anywhere from one to six months. After that, it only shows minor superiority over low-fat diets for certain health markers in people with Type-2 diabetes. 

One of the main reasons for this loss of efficacy is simply that it’s hard to stick to long-term, so adherence drops over time. This phenomenon occurs across all weight loss diets, but seems to be especially common with more restrictive diets, like keto. (2)(5)(14)(16)(17)

Could Worsen Health and Performance

Although keto diets can improve cardiometabolic health and glycemic control in people with overweight, obesity, or Type-2 diabetes, there is some evidence that they can actually worsen cholesterol profiles in athletes and people without Type-2 diabetes. (5)(9) 

Also, although most studies indicate that a keto diet is suitable for athletes, some evidence suggests otherwise. (18) The “keto flu” could certainly get in the way of peak performance for most people!

You Might Lack Certain Nutrients

Because keto diets exclude or severely limit starchy foods like whole grains, fruits, legumes, and root vegetables, they might lack certain vitamins and minerals and require supplementation. These diets are likely low in vitamins A and E, thiamin, folate, B6, calcium, magnesium, iron, and potassium. (19)(20)

While keto can provide plenty of insoluble dietary fiber from fibrous veggies, it may not be as high in soluble fiber, which is more commonly found in starchy vegetables and whole grains. Low fiber intake could have a negative impact on gut microbes, which rely heavily on soluble fiber for energy production. (19)(20)

Unsafe for Certain Health Conditions

Despite its promise for improving Type-2 diabetes symptoms, a keto diet can lead to dangerously low blood sugar, so it shouldn’t be started without medical supervision. People with diabetes are also at risk of developing diabetic ketoacidosis (though this isn’t a concern for people without the condition.) 

It’s also dangerous for people with certain diseases of the liver or pancreas and should be avoided by people with certain metabolic enzyme deficiencies. (1)(20)

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Restrictive diets like the keto diet can also lead to feelings of social isolation and increase the risk of developing disordered eating behaviors. (20) 

People with pre-existing health conditions should check with a health care provider and, ideally, work with a registered dietitian when starting a new diet of any kind.

Common Foods in the Keto Diet

Keto diets generally include meat, poultry, seafood, eggs, cheese, cream, butter, oils, and limited amounts of nuts, seeds, and fibrous veggies like cucumbers, leafy greens, or broccoli. Fruit, bread, grains, starchy veggies (like peas, corn, or lentils), and most dairy products are extremely limited or excluded. (21)

Your Takeaways

What originally began as a medical intervention to treat seizures has morphed into one of the most popular diets in the fitness industry. The keto diet certainly has a lot of research behind it, but that doesn’t necessarily mean it’s a bulletproof solution to your dietary woes.

• The ketogenic, or keto diet involves extreme carbohydrate restriction, amounting to only 5 to 10 percent of total daily caloric intake.
• Instead, keto dieters consume lots of protein and especially calorically-dense dietary fat.
• Keto diets are purported to aid in weight loss, appetite regulation, cardiometabolic health, and seizure suppression for some.
• Restricting yourself to only certain food groups through the keto diet may make it difficult to get enough specific vitamins and minerals.
• Other data show that the ketogenic diet is difficult to adhere to over long periods of time.
• Generally, keto is perfectly safe for both cardio athletes and weight lifters. Carbohydrates are not strictly essential for high-level athletic performance in all cases.

Summary

So, do keto diets really deliver on everything they promise? Sort of. Yes, they can be used for fat loss, which can improve body composition and metabolic health in certain populations. For athletes and people who are already metabolically healthy, keto diets aren’t especially beneficial, and could even be harmful.

Plus, they can be dangerous for people with certain health conditions, and their effects on gut health are still unclear. One of the most significant limitations of keto diets is how unsustainable they are for most people, because the benefits might not matter much if they’re only temporary.

FAQs

Still scratching your head over the ketogenic diet? Here are some answers to common questions:

References

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7. Vargas-Molina, S., Gómez-Urquiza, J. L., García-Romero, J., & Benítez-Porres, J. (2022). Effects of the Ketogenic Diet on Muscle Hypertrophy in Resistance-Trained Men and Women: A Systematic Review and Meta-Analysis. International journal of environmental research and public health, 19(19), 12629. 
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10. Lee, H. S., & Lee, J. (2021). Influences of Ketogenic Diet on Body Fat Percentage, Respiratory Exchange Rate, and Total Cholesterol in Athletes: A Systematic Review and Meta-Analysis. International journal of environmental research and public health, 18(6), 2912. 
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13. Hall, K. D., Chen, K. Y., Guo, J., Lam, Y. Y., Leibel, R. L., Mayer, L. E., Reitman, M. L., Rosenbaum, M., Smith, S. R., Walsh, B. T., & Ravussin, E. (2016). Energy expenditure and body composition changes after an isocaloric ketogenic diet in overweight and obese men. The American journal of clinical nutrition, 104(2), 324–333. 
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18. Burke, L. M., Ross, M. L., Garvican-Lewis, L. A., Welvaert, M., Heikura, I. A., Forbes, S. G., Mirtschin, J. G., Cato, L. E., Strobel, N., Sharma, A. P., & Hawley, J. A. (2017). Low carbohydrate, high fat diet impairs exercise economy and negates the performance benefit from intensified training in elite race walkers. The Journal of physiology, 595(9), 2785–2807.
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21. Merrill, J. D., Soliman, D., Kumar, N., Lim, S., Shariff, A. I., & Yancy, W. S. (2020, May 1). Low-Carbohydrate and Very-Low-Carbohydrate Diets in Patients With Diabetes. Diabetes Spectrum, 33(2), 133-142.
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