What is the keto diet?

What is the Keto Diet?

Reading Time: 6 minutes 62 seconds


Date: 2022-12-09

When it comes to diets aimed at weight loss, the role of the personal trainer is not to choose one for the client but to make sure that he or she is prepared to make an informed choice. That means staying on top of the latest trends, and no weight loss plan is hotter today than the ketogenic (keto) diet.

Like most diets, the keto diet is not for everyone, and there are costs and benefits for those who choose to go on it. With that in mind, here's what fitness professionals need to know.

What a Ketogenic Diet Is & How It Works

The keto diet was first introduced in the 1920s. Initially used to treat childhood epilepsy, many have discovered that it helps with weight loss too. It is a high-fat diet that is also low in carbs. It is similar to the Atkins diet. Except, on Atkins, you are able to introduce carbs back into your diet over time. This does not occur with a ketogenic diet. It is a low-carbohydrate diet from start to finish.

The purpose behind keeping your carbs so low is that it puts (and keeps) your body in ketosis. Ketosis is a metabolic process in which the body burns fat instead of burning glucose. By not eating a lot of carbs, your insulin levels are lower. Your body doesn't release enough insulin to turn your carbs into energy.

When you are in ketosis, you have higher ketone levels. Ketones are acids the liver produces from your excess fat. Once created, these ketones are released into your bloodstream. From there, they are transported to your muscles to be used as fuel.

Following a standard ketogenic diet puts you into ketosis. Another way to increase ketone levels is with exogenous ketones. Exogenous ketones are supplements that help you stay in ketosis without having to watch your carbs so closely.

Why are ketogenic diets so focused on fat? Fat serves many valuable purposes in the human body. It assists with proper cardiovascular and nervous system function. It also aids in metabolism and inflammation. Not to mention, a high-fat diet is also more filling.

Keto Diet Science: What the Research Says

What's the science behind keto? Do ketogenic diets really work? Let's look at what the research says about whether keto actually assists with weight loss.

  • In 2018, the journal Canadian Family Physician published a review of 11 studies. These studies compared a ketogenic diet to a low-fat diet. At 6-24 months, the ketogenic diet group lost roughly 2.2 more kg (4.85 pounds) than the low-fat diet group.

  • The same researchers also looked at 13 studies that compared the longer-term effects of ketogenic diets. After 1-2 years, the weight loss of the ketogenic diet group was 0.9 kg (approximately 1.98 pounds) higher than those on a low-fat diet.

  • A study published in Experimental & Clinical Cardiology involved 83 obese patients, each with a body mass index (BMI) of 35 or higher. All participants also had high glucose and cholesterol levels. After following a ketogenic diet for 24 weeks, their weight and BMI "decreased significantly." Their cholesterol levels lowered as well. Researchers noted that their good cholesterol (HDL) increased and their bad cholesterol (LDL) decreased. Blood glucose also decreased over this time frame.

Keto diet science further reveals that eating this high-fat diet low in carbs is also good for:

  • lowering the risk of some cancers

  • improving heart health

  • protecting the brain and nervous system

  • improving symptoms associated with polycystic ovary syndrome (PCOS)

  • easing epileptic seizures

  • soothing acne inflammations

What a Standard Ketogenic Diet Looks Like

A standard keto meal plan contains roughly 75 percent fat, 15-20 percent protein, and 5-10 percent carbs. These carbs break down into two categories: total carbs and net carbs.

Total carbs is pretty self-explanatory. It is the number of carbohydrates in that food item. Net carbs is total carbs minus fiber. For instance, if the food has 25 grams of carbs and 5 grams of fiber, the net carbs is 20.

Ideally, your net carbs when eating ketogenic should be 25 grams or lower. Though, keeping net carbs to no more than 20 grams helps your body transition into ketosis faster.

Keto diet foods to consider adding to your meal plan include:

  • Red meat

  • Poultry

  • Fatty fish

  • Eggs

  • Nuts and seeds

  • Avocado

  • Low-carb vegetables (tomatoes, onions, leafy greens)

  • Healthy oils (coconut oil, extra virgin olive oil)

Conversely, there are a few keto diet plan foods to limit or avoid. This includes grains, starches, beans, and legumes. Because keto diets are extremely low-carb diets, you also want to limit your consumption of fruit and root vegetables. This keeps your ketones where they should be.

The important thing to remember while trying to increase your ketone bodies is that there are healthy fats and non-healthy fats. Healthy fats are unsaturated fats like those found in olive oil, nuts, seeds, and avocados. Saturated fats aren't so good for you and include butter, lard, and coconut oil. Harvard Medical Center suggests limiting saturated fat intake to less than seven percent of your total daily calories.

Following a Keto Diet Plan and Working Out

There are actually four types of ketogenic diet. We've talked mainly about the standard ketogenic diet. Another version of this low-carbohydrate diet that supports ketosis but also a more active lifestyle is a targeted keto diet.

A targeted keto diet is still a high-fat diet at 65-75 percent fat. However, instead of carbs being limited to 5-10 percent of the daily caloric intake, this ketogenic diet allows 10-15 percent carbs. The remaining 20 percent is protein.

The carbs supply the energy the body needs to engage in high-intensity workouts. The protein assists with recovery. Some research suggests that ketosis may even increase performance of endurance athletes. Ketosis works by decreasing muscle glycolysis and reducing plasma lactate concentrations.

Other studies have found that eating a high-fat, low-carbohydrate diet may hurt performance. This is something to keep in mind whether you strive to eat a diet that is ketogenic or you're working with clients who are on this type of meal plan. If performance begins to decline, following a keto diet plan and working out may not be the best option.

Keto Diet Tips

If you or your clients find that a ketogenic meal plan is difficult to follow all of the time, another option is a cyclical ketogenic diet. This involves following a ketogenic approach five days a week as opposed to all seven.

On a cyclical ketogenic diet, the carbs on off days increases to 50 percent. Protein remains around the same at 25 percent and fat drops to 25 percent as well. This enables your body to produce ketone bodies on your diet days but also gives you a couple of days to eat more of the foods you enjoy.

Also, coconut oil is listed as one of the preferred keto diet plan foods. Since it contains more than 11 grams of saturated fat per tablespoon, your consumption should be limited. Incorporate other fat sources in your meal plan instead. Another option is to use coconut oil more sparingly.

How long should you be on a keto diet? To see results from your ketogenic meal plan typically takes a few months. Whether there any benefits from eating keto long-term is still unclear as Harvard indicates that research in this area is lacking.

A Few Words About the Keto Flu

The body doesn't always easily adapt to keto diet plan foods. Therefore, some who have recently switched to eating ketogenic may experience the keto flu.

The keto flu feels much like the regular flu in that you may have nausea, vomiting, or diarrhea. Sometimes the keto flu causes constipation, headaches, irritability, and weakness. Muscle cramps and soreness, difficulty concentrating, trouble sleeping, and increased sugar cravings may occur.

In most cases, the keto flu lasts a week. As your body beings to adjust to the elevated ketone bodies, symptoms will begin to disappear.

In the meantime, there are a few things you can do to help combat the keto flu. Drink more water, reduce the intensity of your workouts, and make sure you're getting enough macronutrients (fat, protein, and carbs).

Drinking a sports drink that contains electrolytes may help as well. This will help replace some of the nutrients that your body needs to feel better.

Who Should Not Follow a Ketogenic Diet?

If you have type 1 diabetes, high ketone levels can potentially be life-threatening. Individuals trying to control their diabetes should check with their doctor before eating ketogenic for weight loss.

A keto diet is also not recommended for clients who struggle with limiting their saturated fat intake. Because this meal plan is high in fat, some people think they can eat all the unhealthy fats they want. This is not the case. Instead, ketogenic foods should be low in saturated fat to help protect heart health.

To learn more about what foods can help your clients achieve their weight loss goals, the ISSA offers a Nutrition Specialist Certification. This course teaches you how different foods affect the body and sports performance. You also learn how to create a meal plan your clients are able to follow that also helps them reach their goals.


Kephart, W.C., Pledge, C.D., Roberson, P.A., Mumford, P.W., Romero, M.A., Mobley, C.B., Martin, J.S., Young, K.C., Lowery, R.P., Wilson, J.M., Huggins, K.W., Roberts, M.D. "The Three-Month Effects of a Ketogenic Diet on Body Composition, Blood Parameters, and Performance Metrics in CrossFit Trainees: A Pilot Study." Sports 6, no. 1: 1. 2018.

Lange, K.W., Lange, K.M., Makulska-Gerturda, E., Nakamura, Y., Reissmann, A., Kanaya, S., Hauser, J. Ketogenic diets and Alzheimer's disease. Food Science and Human Wellness,Volume 6, Issue 1, March 2017, Pages 1-9. https://doi.org/10.1016/j.fshw.2016.10.003

Oliveira, C.L.P., MSc., Mattingly, S. PhD., Schirrmacher, R., MD., Sawyer, M.B., MD., Fine, E.J., MD., Prado, C.M., PhD., RD. A Nutritional Perspective of Ketogenic Diet in Cancer: A Narrative Review. Journal of the Academy of Nutrition and Dietetics,Volume 118, Issue 4, April 2018, Pages 668-688. https://doi.org/10.1016/j.jand.2017.02.003

Saslow, L. R., Daubenmier, J. J., Moskowitz, J. T., Kim, S., Murphy, E. J., Phinney, S. D., Hecht, F. M. (2017). Twelve-month outcomes of a randomized trial of a moderate-carbohydrate versus very low-carbohydrate diet in overweight adults with type 2 diabetes mellitus or prediabetes. Nutrition & Diabetes, 7, 1-6. Doi: https://dx.doi.org.ezproxy.liberty.edu/10.1038/s41387-017-0006-9

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