Probably the most discussed dietary plan in the nutrition world during the past few years is the ketogenic diet (KD). It’s been making waves in research with diabetics, overweight individuals, and in the sports industry.

What is it?

The KD is heavily restrictive of carbohydrates, moderate in dietary protein amounts, and high in dietary fat. The concept is that the KD causes your body to switch from burning carbohydrates for fuel to almost exclusively burning fat, and, when this occurs, your body is in a state of nutritional ketosis.

This dietary approach should not be confused with a “low-carb” or “paleo” diet, in which more dietary carbohydrates are typically allowed and the body might not attain a state of nutritional ketosis.

A ketogenic diet is often thought of as what our ancestors ate when they hunted and gathered – meats, berries, nuts, and vegetables. This strict, but tasty dietary plan has been used as a treatment option for epilepsy for more than a century, and in the past few decades has been used for individuals who have metabolic syndrome or type 2 diabetes.

What is ketosis?

The liver breaks down fatty acids when carbohydrates are not available. Also, via gluconeogenesis, non-fatty acids (protein or lactate, for example) are broken down. Ketones are the byproducts of both reactions – in the form of acetoacetate, beta-hydroxybutyrate, and acetone.

Nutritional ketosis is attained when the body makes ketones because of dietary reasons (such as the ketogenic diet).

Ketosis can also occur because of starvation, excessive or prolonged exercise, alcoholism, or uncontrolled type 1 diabetes. It can take days or even weeks for the body to start making ketones. Once ketosis does begin you might notice an acetone (nail polish-like) or fruity smell on the breath. Ketones will be present in the blood (1-3 mmol/L) or urine.

Nutritional ketosis is not to be confused with diabetic ketoacidosis, which is a life-threatening state in diabetics when ketone levels increase to 5 mmol/L or higher.

What does the research say?

Research shows a therapeutic potential of the KD in various pathological conditions, such as type 2 diabetes, polycystic ovary syndrome, acne, neurological diseases, cancer, and improvement of respiratory and cardiovascular disease risk factors.1

A study of 300 adults who had type 2 diabetes found that education followed by close evaluation and monitoring of nutritional ketosis is highly effective in improving glycemic control and weight loss, while significantly decreasing the need for blood-sugar lowering medications.2

Despite the high saturated fat intake while on this diet – sometimes 40 percent or more of fat calories – multiple studies show the plasma concentration of saturated fats does not increase.

This suggests that consuming foods high in saturated fat – in the absence of carbohydrates – does not increase the risk for cardiovascular disease.3,4

And we see benefits in athletes too. Compared to a high-carbohydrate diet group, 12 weeks of a KD and training consisting of high intensity-interval training, endurance exercises, and strength exercises, enhanced body composition, fat oxidation during exercise, and specific measures of performance relevant to competitive endurance athletes.5

There were also noted benefits of improved testosterone while following the KD.6

The KD is a good dietary option for athletes. In ultra-endurance athletes running 100 miles or ironman distance triathlons, eating a KD resulted in maintenance of higher levels of fat oxidation throughout exercise and less dramatic change in glycogen stores.7

Studies also show strength athletes optimize weight class without compromising power output.8

How do I start a KD?

In a well-formulated KD, you can meet all your dietary needs for growth, sports, healing, recovery, or other metabolic needs. If you are taking any medications, you should first consult with your health-care professional – particularly if you take a medication for blood sugar, blood pressure, or kidney function.

It will be important to monitor your medication doses, timing, and needs throughout the KD. Then work with a dietitian to design a well-formulated KD consisting of foods and amounts that work for you and your lifestyle. You will probably start by calculating a total carbohydrate amount that you can consume daily for maximal benefits.

The amount of carbohydrate restriction will depend on how well your body metabolizes carbs.

For most individuals, 30-60 grams of carbs daily will enable you to achieve ketosis, with those who are insulin resistant on the lower end.

 Protein will be consumed in an adequate and moderate amount, typically between 1.2 and 2.0 grams per kilogram of body weight – or about 15-25 percent of total calories.

It is important not to over-consume protein, because some amino acids in excess are glucogenic (converted to glucose) and insulinogenic (stimulate an insulin response to the glucose). But it is also important to eat enough protein so your lean muscle mass isn’t compromised.

Fat calories will comprise the rest of your total calories for the day, typically around 70 percent of total calories.

Consuming this much fat is typically the hardest part of the KD for most individuals to adjust to, since it can be vastly different from their usual intake. It usually requires choosing protein sources that also provide fats.

In the first days and weeks, as your body depletes its carbohydrate (glycogen) stores, you will see great daily changes in weight. These early weight changes are most likely water loss; glycogen molecules hold onto water, so as these molecules are metabolized, water is released and excreted.

Therefore, electrolyte balance is greatly important during the early weeks of the KD – especially sodium and magnesium. You will want to ensure you are supplementing with extra electrolytes to avoid any imbalances.

What foods can I eat?

Almost any foods that don’t contain carbohydrates are allowed on the KD, although some options are better than others. Look for fish and natural meats like beef, pork, and poultry.

Eggs, full-fat dairy products, nuts and seeds, and low-sugar fruits, like berries or coconut, are also acceptable.

Non-starchy vegetables will make up the bulk of the fiber you will get in your diet. Oils, creams, butter, and other fat sources are plentiful. Alcohol consumption should be kept to a minimum, and, if you do partake, dry wines or clear distilled liquors tend to have lower or no carbohydrates.

Cut out all high-sugar fruits and juices, starchy vegetables, grains, legumes, and sugar-based sweeteners.

You should consider avoiding packaged items that are sugar-free or contain sugar alcohols because they can cause GI upset. Read labels on everything you can, and when eating away from home be sure to inquire about how foods may have been stuffed or breaded, and the ingredients in sauces.

What are the benefits?

There is growing research that supports the benefits of the KD in several populations. The KD can support blood sugar control, cholesterol levels, weight management and metabolism, and athletic endeavors.9

The KD is gluten-free, and you can also make it a low or lactose-free diet. Individuals with other dietary restrictions, either personal or medical, can make the KD work for them if it’s well formulated.

Many individuals have reported fewer energy swings or the mid-afternoon slumps that are often experienced after a heavy carbohydrate meal.

Virtually all of your favorite meals can be turned into a ketogenic-friendly alternative, and there are many pre-made food and snack options in the grocery store – particularly in natural foods stores.

What are the drawbacks?

There are not many drawbacks, although there are anecdotal reports of low energy or headaches during the first few weeks of the diet – possible due to electrolyte imbalances – which usually last only a week or two.

You could find yourself having issues at certain restaurants – like Italian restaurants full of pasta and pizza options – or at convenience stores.

The best advice is to look for menus online or pack appropriate snacks so you don’t get hungry watching people eat.

Whether or not you think the ketogenic diet is right for you, it is important to understand and recognize its effective use in certain populations. If you are considering a KD lifestyle for yourself, then know it takes consistency and patience, but the outcomes can be rewarding. 


References

1.     Paoli A, Rubini A, Volek J, Grimaldi K. Beyond weight loss: a review of the therapeutic uses of very-low-carbohydrate (ketogenic) diets. Eur J Clin Nutr 2013;67(8):789-796.

2.     McKenzie A, Hallberg S, Creighton B, et al. A novel intervention including individualized nutritional recommendations reduces hemoglobin A1c level, medication use, and weight in type 2 diabetes. JMIR Diabetes 2017;2(1):e5.

3.     Forsythe C, Phinney S, Feinman R, et al. Limited effect of dietary saturated fat on plasma saturated fat in the context of a low carbohydrate diet. Lipids 2010;45(10):947-962.

4.     Volk B, Kunces L, Freidenreich D, et al. Effects of step-wise increases in dietary carbohydrate on circulating saturated fatty acids and palmitoleic acid in adults with metabolic syndrome. PLoS One 2014;9(11):e113605.

5.     McSwiney F, Wardrop B, Hyde P, et al. Keto-adaptation enhances exercise performance and body composition responses to training in endurance athletes. Metabolism 2018;81:25-34.

6.     Wilson J, Lowery R, Roberts M, et al. The effects of ketogenic dieting on body composition, strength, power, and hormonal profiles in resistance training males. J Strength Cond Res 2017 April. doi:10.1519/JSC.0000000000001935

7.     Volek J, Freidenreich D, Saenz C, et al. Metabolic characteristics of keto-adapted ultra-endurance runners. Metabolism 2016;65(3):100-110.

8.     Greene D, Varley B, Hartwig T, et al. A low-carbohydrate ketogenic diet reduces body mass without compromising performance in powerlifting and Olympic weightlifting athletes. J Strength Cond Res 2018;32(12):3373-3382.

9.     Dashti H, Mathew T, Hussein T, et al. Long-term effects of a ketogenic diet in obese patients. Exp Clin Cardiol 2004;9(3):200-205.