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A Dietitian's Thoughts on the Ketogenic Diet

Updated: Jul 5, 2020

Here is my *quick* run-down of this popular diet.

Carbohydrates are my life blood-truly. Pasta, bread, rice, chocolate-yes, please! Carbohydrates are our bodies preferred and primary source of fuel, and used exclusively by our brain and central nervous system. For athletes, this means that when you are looking to perform your best, utilizing strategies to maximize carbohydrate stores will be key to optimal performance.

For athletes, carbohydrates will provide the most efficient source of energy for endurance and athletic performance.

So What Is the Ketogenic Diet?

Very low carbohydrate (5% of total intake), about 20-50 grams of carbohydrate allowed per day (for reference; 1 medium banana as about 27 grams of carbohydrate), with moderate protein (10% of total intake) and high fat (75-90% of total intake). What many people do not realize is that protein can be converted into glucose in our bodies. Glucose is what food sources of carbohydrates are broken down into for our bodies to use. Our body is resourceful in this way, as food sources of protein may also be broken down and converted to a form of glucose to provide us energy.

So What Is the Goal of this Diet?

Proponents of this diet are looking to change the body's metabolism by adjusting the primary energy source from glucose (carbohydrates) to fat. This switch would eventually lead to a state called, "Ketosis", where the body would be using fat to fuel the body.

Originally, before this was publicized as a dietary pattern for the public, this diet was (and is) used to help reduce seizures in children. This diet was not intended as a 1st or 2nd line of defense, but actually as a 3rd treatment option if the first 2 interventions did not reduce the seizures. If the children were put on this diet, they were monitored closely by healthcare professionals due to the likelihood for the child to go into a potentially fatal state of "Ketoacidosis". This occurs when ketones, a byproduct of fat metabolism, are found in high rates in the blood stream. This will subsequently lower the acidity of the blood to harmful and therefore lethal levels. This diet was not meant to be long term for the children.

What are the Health Claims?

The main reasons I have heard and seen individuals choose to partake in this diet is for; weight loss, reduced appetite (ketones potentially affecting appetite control hormones-again, only in the short term), improving insulin sensitivity/glycemic control, and decreasing LDL cholesterol.

Like many diets, the Ketogenic diet does lead to weight loss - although in the short term. Due to the incredibly restrictive nature of the diet (cutting out a major food group), it is next to impossible to sustain for greater than 1 year. This tracks with the state of weight - based interventions that do not work for an estimated 80% of people that undergo them. The percentage of "successful" weight loss attempts starts to decrease after the 1 year mark.

Research suggests that following a Ketogenic diet can reduce appetite by the ketones produced from the breakdown of fat. The ketones may potentially affect appetite control hormones that subsequently decrease appetite. Although this finding is also only shown to have short term effects. For those with poor insulin sensitivity/glycemic control (i.e. high Hemoglobin A1c's), following a Ketogenic-type diet showed a decrease in their Hemoglobin A1c's, although it is still unclear if the dietary choices were what actually improved their A1c levels. In regards to LDL-cholesterol, the effects are minimal at best.

Why this Dietitian does not Recommend the Ketogenic Diet

1. The majority of the research that shows this diet is effective and truly health promoting is in children with epilepsy - not the average, healthy, adult population. Therefore, the health claims/findings in the current, limited research on adults have only proven short term and not long-term benefits.

2. It is very difficult to sustain and puts the individual at risk for nutrient deficiencies. It cuts out whole food groups, such as; legumes, whole grains, fruit, starchy vegetables. These all are sources of fiber, vitamins&minerals, antioxidants and phytochemicals.

3. It puts the individual at risk of developing disordered eating behaviors, negative body image and social isolation. Because of the restrictive nature of the diet, individuals may miss out on social gatherings or special family events for fear of "breaking" their diet.

4. For athletes, only one study has looked at the effect of following a Ketogenic diet with well - trained endurance athletes. It concluded the chronic adaptations from following a diet so high in fat (80% of total calories) was able to (at best) maintain endurance capacity for only a moderate working intensity and sacrificed the ability/desire to exercise at higher workloads. This means that you are not going to perform your best and it's going to feel much harder to keep - up this less - than - ideal pace. Similar to endurance athletes, very little studies have been done for power athletes. The current data on endurance athletes, though, suggests that no enhancement in performance would be seen in power athletes, either.

Bottom Line: any diet that cuts out whole food groups is not something I will advise my athletes, or the general, healthy population to partake in. They also concluded that the data suggest that reducing carbohydrates to less than 50 g per day is unnecessary.

Thanks for being here.

Maddi Osburn RDN LD



- Paoli A. Ketogenic diet for obesity: friend or foe?Int J Environ Res Public Health.

- Paoli A, Bosco G, Camporesi EM, Mangar D. Ketosis, ketogenic diet and food intake control: a complex relationship.Front Psychol. 2015;2;6:27.

- Gibson AA, Seimon RV, Lee CM, et al. Do ketogenic diets really suppress appetite? A systematic review and meta-analysis.Obes Rev. 2015;16(1):64-76.

- Saslow LR, Daubenmier JJ, Moskowitz JT, et al. Twelve-month outcomes of a randomized trial of moderate-carbohydrate versus very low-carbohydrate diet in overweight adults with type 2 diabetes mellitus or prediabetes.Nutr Diabetes. 2017;7(12):304.


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