Whenever I have a long day in the saddle, there are a few cardinal rules I know to follow: always bring more hydration than I think I need, slather on sunscreen and chamois cream, and bring lots of snacks – the better, the better .
The latter is a no-brainer for endurance athletes. “Athletes are taught from an early age that carbohydrates are essential for fueling exercise,” says Mitchell Zandes, RD, a registered dietitian and certified strength and conditioning coach in New York City.
But lately I’ve had to break that rule when experimenting with the ketogenic diet. Perhaps the most crucial part of the keto diet is limiting your carbohydrate intake to about 25 to 50 grams per day, or just 5 to 10 percent of your total calorie intake, says Rob Raponi, a naturopathic doctor and certified sports nutritionist in Ontario.
Doing this can put your body into ketosis, a state in which it begins to turn to ketones (or stored fat) as its primary energy source instead of the glucose that comes from carbohydrates. (Another important part of the keto diet is increasing your fat intake to about 75 to 80 percent of your total calorie intake.)
Although I was eager to experiment with a new diet, I wasn’t willing to change my normal riding routine. I had a 62 mile charity ride through the hills of Rye, New Hampshire that I couldn’t miss. Would I survive the training – not to mention the ride itself – eating so few carbs? And ultimately: does keto work for endurance athletes, period?
It was a legitimate concern. “With products like Gatorade and rituals like ‘pasta parties’ before major events, limiting carbs entirely is a counterintuitive and strange practice,” Zandes explains.
What endurance athletes need to know about Keto
Many think the Keto diet is brand new, but it has actually been around for a long time. Doctors used it in the 1920s as part of a therapy plan for people diagnosed with epilepsy. They noticed that patients who followed it essentially tricked their bodies into thinking they were starving, ultimately resulting in fewer seizures. But with the development of antiepileptic drugs, the diet became more or less useless after a while and faded into the background.
The ketogenic diet works by training your body to enter a state of ketosis. When glucose — an essential energy source for all cells in your body — runs out, the liver can produce ketone bodies from fatty acids, explains Namrita Brooke, Ph.D., RDN, sports dietitian and adjunct professor in the Department of Exercise Science and Health at the University of West Florida. The ketone bodies then become an additional source of energy for the body in times of glucose depletion.
“It should be noted, however, that high-fat, low-carb diets that are not ketogenic can also increase the availability of fatty acids available for fuel without having to deplete glucose,” Brooke explains. “Pro peloton cyclists use exogenous ketone supplements to have that extra fuel source without having to deplete the body of essential carbohydrates and glucose for energy.”
Thanks to the recent buzz about this diet, the exogenous ketone supplements in the Peloton, and the appeal of quick weight loss claims, the general population and some athletes have started experimenting with the keto diet again. Many people – especially endurance athletes – wonder: does keto work?
During the first two weeks of training on the Keto diet, I felt a lot more brain fog than normal, and just the thought of cardio intervals made me want to cry. My performance dropped across the board – although strength training was definitely easier to perform – and I was constantly wondering if I could actually survive my upcoming ride on so few carbs. But I bounced back around the two-week mark and learned a few things.
4 Tips for Following the Keto Diet
However, the main secret to my success wasn’t sticking to the first two weeks of workouts. I still had to implement smart strategies that kept my body performing at its best. That’s why I focused less on intervals and more on steady riding on my long rides.
“When it comes to ultra-endurance, or when it comes to doing a long ride and not a race, [the keto diet] can work,” says Menacham Brodie, head coach of Human Vortex Training and coach of USA Cycling. “Carbohydrates are important for the body because we need them for energy bursts. [They’re] essentially broken down into blood glucose, which is quickly available to our energy systems.” And cycling often requires quick bursts of energy and intense work, so you need carbohydrates to get the job done.
As long as I didn’t need an immediate burst of energy—and instead kept a consistent pace—I could complete these 62 miles on little to no carbs. Here’s what else the experts suggested we try.
1. Focus on your macros
One of the first questions I had when I started the keto diet was whether I should eat more carbs on heavy exercise days, or if this would kick me out of ketosis.
While there isn’t a black and white answer yet, the good news is that every athlete is a study in one, Brodie says. This means that as long as you regularly test to see if you’re in ketosis (via urine strips or a blood glucose meter), you can keep a close eye on what your body can handle. This is important because if your buddy tells you he’s on the Keto diet, and you just to have to try, but he doesn’t test himself, he doesn’t do it right.
Instead of focusing on hitting a certain number of grams per day, Raponi thinks it’s smarter to track your keto diet using macro percentages. In any case, your calorie needs change based on your energy production and “the amount of energy expended.” [during exercise] means that carbohydrates are continually depleted, leaving the body in a state of ketosis as long as the right amount of fats and proteins are consumed,” he explains.
This also helps avoid the common mistake of underconsumption of calories, which can lead to problems such as low energy availability and REDS, says Brooke. “However, there is increasing evidence that even low carbohydrate availability during exercise can have an impact on immune and hormonal disruption, similar to low energy availability,” she adds.
Keep in mind: “A more forgiving option would be a carb-period diet to optimize metabolic flexibility, and experimenting with exogenous ketones to see if they boost your performance,” says Brooke.
2. Experiment with your fuel
Since cyclists have the advantage of being able to pack more whole foods during endurance events than, say, runners, I left my usual gels and high-carb bananas at home and tested keto-friendly options that I thought would work well for my stomach. : walnuts, cashew nuts,and pickles.
But just because something works for me doesn’t mean it’s the gold standard. “The most important thing is that an athlete learns by doing,” says Zandes. “All ketogenic diets have the same underlying principles, but the details of meal timing and snack choices can vary greatly.” (Other snack options: sliced avocado, cheese, and nut butters.)
3. Hydrate, hydrate, hydrate
“Fat-adapted athletes should still make hydration a priority, [as] excessive sweat losses will result in losses of sodium and potassium, which must be replenished to maintain exercise intensity,” says Zandes.
The only problem? Gatorade and similar sports drinks are not on the keto-approved list due to their high sugar content. Instead, try low-carb, low-sugar Nuun Electrolyte tablets.
Raponi also suggests supplementing with exogenous ketones, which are sold as a powder that can be mixed in water. “In theory, someone on a ketogenic diet is burning off these ketones for energy,” he explains, so supplementing with them provides a new source of fuel.
4. Make sure you have a reserve of carbohydrates
You never know what will happen along the way. No matter how prepared you think you are, it can affect everyone differently. According to Brodie, there are some indicators that the diet is probably not working. “Usually the first thing is you have a large amount of energy, like someone turned a switch and you just can’t go on anymore,” he says. “It’s not banging; it’s like the pedals are turning, but no one is home.”
Then comes the dizziness. If the dizziness refuses to go away despite more keto-friendly fuel and hydration, it’s time to turn to carbs, and having an emergency supply can be helpful.
Brodie suggests cutting half a bottle of a sports drink like Gatorade with water and chewing on dry dates.
Within about 10 to 20 minutes you should be able to recover and finish the ride strong, but take your time and don’t rush. And in the end, that’s what it’s all about, because when you’re forced to choose between ketosis and finishing something that matters, it’s clear that a diet is always meant to be broken.
Bottom line: Does Keto work?
Despite misconceptions, the keto diet be able to work for endurance athletes, especially for maintaining a steady pace at low intensity. However, many forms of cycling require a short effort, such as climbing a hill, and that requires carbohydrates that are readily available.
Following the keto diet takes planning and dedication to reap the benefits of staying in ketosis. Although you should stick to the basic rules of the diet, it is also important to adapt it to your own needs. Just know that periods of intense exercise require extra carbohydrates, and a supplement with exogenous ketones can help support your performance.
If you find that the diet isn’t working for you – and of course if your doctor doesn’t recommend it – there’s no need to delve into the trendy way of eating.
Samantha Lefave is an experienced fitness, health and travel writer and editor. She regularly interviews top athletes, top trainers and nutritionists from the top of their field; her work has appeared in Runner’s world, Misuse, Outside, Men’s health And Women’s health, Cosmopolitan, Glamourand more.
Dr. Namrita Brooke is a full-time endurance sports coach and sports nutritionist who advises active individuals and amateurs to professional athletes. She is also an adjunct professor in the Department of Kinesiology and Health at the University of West Florida. Professionally, she also serves on the Editorial Board of the Sports Nutrition Care Manual and remains involved in nutrition and exercise research, student mentoring and coach development. Namrita’s personal athletic experience ranges from ultra-endurance mountain biking to off-road triathlon, cross-country mountain biking, gravel biking, duathlon, cyclocross, running and trail running. Her research background includes research into hydration and sports drinks, and the interaction between diet, physical activity and the brain.