The Keto Diet for Athletes?
What do fruits, starchy vegetables, grains, most dairy products, nuts, seeds, beans, legumes, and toothpaste all have in common?
They contain a decent amount of carbohydrates.
The growing popularity of the keto diet (a.k.a., high-fat, very low carbohydrate) has inevitably entered the arena of sports--and not necessarily to help improve an athlete's performance, but to help reduce body fat.
Google Image's top results for "keto"
Source: Google
What is the Keto Diet?
The keto diet doesn't have a specific definition, but here's what I was able to find:
Less than 5-10% of total calories derived from carbohydrates: For a 2,000-calorie diet, this means 25-50 grams of carbohydrate per day.
Hard-and-fast rule of 25-50 grams of carbohydrate per day: Clients I've met with typically default to this range. But think about it: Should a 220-lb. linebacker and a 110-lb. ballerina ever have the same nutritional goals? No.
Described as ratios ranging from 4:1 to 6:1 carbohydrate-to-fat/protein: For 4:1, this means that there are four times as many fat grams as there are carbohydrates and protein combined. For 6:1, the amount of grams stemming from fat would then be higher.
What is Ketosis?
At rest, the body burns a combination of carbohydrates and fat for energy. If the body is not being fed adequate amounts of carbs or calories, the liver begins to convert fat into ketones that can then be used for fuel. Ketone production is how the body responds to starvation.
When eating keto, the goal is to constantly remain in a state of producing ketones (a.k.a., ketosis).
Are Keto Diets Appropriate for Athletes?
"A major goal of endurance training for the competitive athlete is to promote physiological and metabolic adaptations that increase the ability to sustain the highest average power output or speed of movement for a given distance." - Hawley & Leckey.
We use a mixture of energy systems while exercising. Keto for athletes revolves around the idea that restricting dietary carbs allows the body to tap into its fat reserves for fuel during activity, while sparing muscle glycogen (i.e., stored carbs).
What does the research say regarding keto diets (versus a high-carb or mixed-nutrient diet)?
Well-trained cyclists performed worse during a 1-kilometer sprint power output test.
Impaired high-intensity outputs due to a reduction in pyruvate dehydrogenase activity and glycogenolysis (i.e., muscle glycogen breakdown).
Elite race walkers required more oxygen for the same results (i.e., exercise efficiency decreased).
Impaired ability to sustain a high-intensity level over a prolonged period of time.
No difference in endurance capacity was found during low-to-moderate intensity exercise.
For weight lifters, lean body mass, power, and strength all improved.
Why is sprinting and power output impaired? On a keto diet, the body becomes better at burning fat--and worse at burning carbohydrates. If an athlete only trains for 50-meter sprints and then wonders why they can't finish a marathon, they haven't trained for their sport. This is the same idea when training pathways within the body.
Cheat Days and Meals Exist on the Keto Diet, Yeah?
Probably not.
This is because there's minimal evidence describing:
How long a person needs to eat keto in order to switch into ketosis.
The amount of carbohydrate needed to fall out of ketosis: Does how many carbs in a single meal matter (e.g., Thanksgiving dinner)? And/or does the amount for an entire day matter (e.g., binge day)?
How long it takes to enter back into ketosis after a cheat day: Will the time to ketosis be the same as it was at the beginning of the diet? Or is it shorter because the body has been primed?
That being said, a lot of keto clients I've met don't test their urine for ketones--they use the diet simply for easy-to-follow food restriction rules with the end goal of weight loss. For them, a cheat day won't matter.
But if your athlete's goal is ketosis, then a cheat day will likely matter. They'll see their urine ketone levels drop.
My Approach When Athletes Ask About Keto
Like any diet scenario, I listen, find out more about the athlete's decision-making process, communicate the research, and then apply the research to the athlete sitting before me.
Listen to what interests them about the keto diet: Hint: It's usually for body fat loss--not improving their athletic performance.
Ask where they learned about the keto diet:
If it's an influential teammate or coach then you can expect others on the team are likely thinking about the diet as well (i.e., upcoming team education topic!).
If an athlete notices the bulging muscles and low-body fat levels of their strength coach and catches wind that they're following a keto diet, it's unsurprising that an athlete would think keto works. However, keeping performance goals and energy systems required for their sport in mind are key.
Perform a dietary recall of a typical day that includes their training schedule: Reviewing what they're currently eating, when, and what their fuel go-tos are for training and recovery (and why they select these items).
Review the science: Explain how keto diets relate to the athlete's specific sport, position, and/or event distance.
Circle back to how keto will impact them: With their diet record in hand, review how few carbohydrates the athlete would be consuming in a day and point out what items the athlete is currently consuming that are considered carbs (I do this with a highlighter). Discuss how and why the athlete is using carbohydrates before, during, and after their training. Are they ready to let these foods go? Are they willing to switch up their training and game-day rituals? Plus, what is the likelihood of eating keto at a school's fueling station or dining hall, while traveling, or during a pre-game meal?
Take-away Message: Keto Helps With Weight Loss, But Not Athletic Performance
If an athlete wants to lose body fat, see if they're open to focusing on areas contributing to undesirable weight gain (i.e., alcohol, stress eating) while reminding them that a keto diet will likely hurt their athletic performance.
Calorie deficits aid in weight loss regardless of diet type: Keto dieters have limited options regarding what they can eat, so the monotony can very much help with weight loss.
Once keto ends, will the undesirable weight return? Probably. Like any diet pursued for weight loss, once it disappears as do the dietary restrictions. Reintroducing once-restricted foods will likely lead to weight gain, and possibly result in a higher body weight than before the keto diet was ever pursued.
If an athlete is absolutely set on keto:
Support them if they're dead set on pursuing the diet today: I would rather remain included in an athlete's care even if I quietly disagree with their decision. Being involved allows the health professional to monitor the rate and volume of weight loss, field questions, help with recipe creativity, and maintain the athlete's trust. At the athlete's consent, keep coaching in the loop.
Keep it to the off-season: Remain in contact with the athlete (see above for reasoning).
Focus on protein: With calorie restriction, an increased daily protein dose will help with satiety between meals and mitigate the loss of lean body mass.
Add a multivitamin: At a minimum! Review the foods the athlete wants to consistently consume and fill in the micronutrient deficiencies as appropriate.
Monitor their blood cholesterol: If whipping cream, cheese, and other animal products are the cornerstones of the diet, be aware of cholesterol levels and heart disease risk.
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