The ketogenic diet, characterized by high fat, moderate protein, and very low carbohydrate intake, has gained popularity among athletes. Originally a medical therapy for epilepsy, it has shown potential in reducing weight and body fat. This article explores the benefits and risks of the ketogenic diet for athletes.
What is a Ketogenic Diet?
A keto diet is generally defined as a high-fat, moderate-protein and very-low-carbohydrate diet, consisting of 75 per cent fat, 25 per cent protein and 5 per cent carbohydrates. The keto diet reduces your total carb intake to less than 50 grams a day. This is the equivalent of a cup of white rice. The keto diet excludes carb-rich foods like grains, beans, fruits and starchy vegetables.
How Ketosis Works
The keto diet limits carbohydrates, forcing your body to burn fat for fuel instead. When these stores are full, they are converted into fat. In this state, your body breaks down fats into molecules called ketones. Ketones serve as an alternative fuel source. Being on ketosis leads to low insulin levels and promotes fat oxidation by allowing fats to move from the cell to the circulation. This process of breaking down fats to provide energy leads to a state called ketosis, which happens in 3-4 days.
Benefits of a Ketogenic Diet for Athletes
Weight Reduction and Body Composition
A ketogenic diet has shown to reduce weight by causing a reduction in fat-free mass and lipid synthesis and increase in lipolysis and fat metabolism. This can be used for athletes looking to cut down weight.A keto diet has also been shown to maintain muscle mass as it reduces gluconeogenesis during ketosis and preserves muscle mass, causing a muscle-sparing effect. There is still no positive observation in terms of gaining muscle mass.
Glycogen Preservation
With a keto diet, there is an increased ability to preserve glycogen stores from depleting during exercise. It also stimulates the release, transport, uptake and utilization of fat in the muscle to convert as energy.
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Enhanced Fat Metabolism
During low-intensity activities, fat becomes the major source of fuel, and with a keto diet, there is increased efficiency of fat metabolism and usage. It also prevents muscle glycogen depletion, preventing the early onset of fatigue.
Blood Sugar and Insulin Balance
The main benefit of keto remains its power to keep blood sugar and insulin levels balanced which controls hunger and cravings. The practice of maintaining a keto diet plan results in stable energy levels which helps athletes maintain their nutrition plan without constant food cravings.
Muscle Preservation
Athletes who consume high amounts of protein and fat in their diet will sustain their strength levels because protein together with healthy fats function as "slow" fuel unlike simple carbohydrates which serve as quick source of energy.
Reduced inflammation
For those who may not have considered a Keto diet, the fundamental idea is that when healthy fats (good fats) such as omega-3, omega-6, etc. are emphasized and sugars and inflammatory processed carbs are severely reduced, keto can support healthy joints and repair of muscle tissue. Many athletes report less stiffness and soreness, faster regeneration of muscle, and an overall dominant feeling of preparedness for the next training session.
Mental Clarity
A great benefit of keto is that it stabilizes blood sugar levels and preventing brain fog and energy crashes. When on Keto, instead of relying on glucose, the brain switches to fuel from ketones, which provide efficient fuelling for stable energy, focus, and clarity in mental tasks.
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Metabolic Flexibility
The best thing about the ketogenic diet is its capacity to retrain your body to burn fat as your primary source of fuel instead of sugar. And when an athlete consumes less carbohydrate, the metabolism often switches to one of higher fat oxidation, which allows the body to strip out fat stores for energy instead of using valuable glycogen stores.
Risks and Considerations
Initial Adaptation Period
However, it takes 3-5 weeks to adapt to the diet, and there might be a possibility of having keto fever, as mentioned earlier. Being keto-adapted means your body has now efficiently started to use fats and ketones as the major fuel source for the muscle and the brain-ketones can move across the blood-brain barrier, similar to glucose. Once the glucose stores get depleted, there is a possibility of getting keto flu as the body starts fighting back as a natural response due to low glucose. This may leave you feeling less energetic and lethargic.
Impact on High-Intensity Performance
However, it has been observed that high-fat diets do not improve exercise performance at high intensities as much, as they lower muscle glycogen stores by 50 per cent and lead to fatigue and impaired performance. Such diets also reduced performance timings and benefits due to increased oxygen utilization (fat oxidation uses more oxygen compared to carbs to provide adenosine triphosphate or ATP). The research suggests that short-burst, high-intensity activities like sprints, jumps, heavy lifts, etc. will be negatively affected by a keto diet.
Nutrient Deficiencies
Because the keto diet is so restricted, you’re not receiving the nutrients - vitamins, minerals, fibers - that you get from fresh fruits, legumes, vegetables and whole grains. This could impact muscle recovery, digestion and overall health. People report feeling foggy, irritable, nauseous and tired. “In particular, low fiber intake can disrupt gut microbiota and lead to chronic constipation, while inadequate magnesium, vitamin C and potassium can contribute to muscle cramps, fatigue and weakened immune function,” explains Dr.
Heart Health Concerns
The high-fat nature of the diet could also have negative impacts on heart health. The American Heart Association recommends limiting saturated fat intake to less than 6%. “In practice, many people eat high amounts of saturated fats, which could increase your risk of heart disease,” says Dr. Cheema. “You may be eating a lot of fatty meat thinking it’s a good thing for you because it's high in fat. This can dramatically alter your lipid profile. While high-fat diets can elevate LDL (“bad”) cholesterol, the type of saturated fat matters. The bottom line is that having more fats in your diet can lead to higher cholesterol. “We know that higher cholesterol tends to increase your chances of heart attacks and strokes,” says Dr. Cheema.
Read also: The Keto-Brain Fog Link
Kidney Issues
The keto diet may not be appropriate for everyone, specifically people with kidney disease. “Although more research is needed in that area, there is some suggestion that it can make kidney disease worse over time,” says Dr. Some people also experience dehydration on the keto diet because they’re eliminating glycogen, which holds water, from the bloodstream.
Blood Pressure and Blood Sugar Drops
The keto diet can cause your blood pressure to drop in the short term due to a reduction in blood volume and changes in your fluid balance. Symptoms of low blood pressure include dizziness, lightheadedness or fainting, especially when standing up quickly. Following a keto diet can also cause your blood sugar to drop, which can be dangerous for people living with diabetes. Common symptoms of low blood sugar include weakness or shaking, sweating, a fast heartbeat and dizziness.
Psychological Distress
When you micromanage your food intake by tracking how much you eat, it disconnects you from what your body is asking for. You start using outside numbers to determine what to eat instead of listening to your body. “Being intuitive and understanding what your body needs is essential for proper nourishment,” says Merneedi. Monitoring food so closely can lead to psychological distress, such as shame and binge eating.
Hydration and Electrolyte Balance
Maintaining proper hydration on a keto diet as more loss of fluid and electrolytes is observed due to low insulin levels. Insulin allows the kidneys to store sodium, and sodium is filtered out of the body with low insulin. There are also increased levels of uric acid. To reduce sodium imbalance and uric acid build-up, maintain functions of tissues, reduce the risk of keto flu, and improve performance, it is necessary to consume enough fluids. Sodium can be included by consuming salty nuts or adding more salt to your meals. Potassium, present in avocado, and magnesium, found in pumpkin seeds can also be supplemented.
Difficulty in Sticking to the Diet
Because of the stringent food restrictions, many find the keto diet hard to stick to. “The ketogenic diet can be effective for weight loss when used in a short time period followed by the adoption of healthier eating habits,” says Baljash Singh Cheema, MD, a cardiologist at Northwestern Medicine Bluhm Cardiovascular Institute. “However, we know in studies of these types of diets that once people stop following that diet, they regain at least half of the weight that they lost. Ketosis is difficult to achieve because it’s like a light switch: either on or off. Individuals who consistently track food intake are more likely to remain in ketosis.
Strategies to Mitigate Risks
Strategic Carb Intake
Under such circumstances, periodic carb meals can be included around training to support high-intensity activities. Having a strategic carb day can also help in fuelling the body with 300-350 grams of carbs per day. This also allows you to get back to ketosis easily once you are keto-adapted.
Nutrient Supplementation
Most people following a strict keto diet should take a multivitamin with minerals to ensure they're meeting those vitamin and mineral needs.
Consulting a Nutritionist
If you do opt for a ketogenic diet, it’s important to follow a plan designed by a nutritionist - or even work directly with someone experienced with these diets.
Staying Hydrated
Maintaining proper hydration on a keto diet as more loss of fluid and electrolytes is observed due to low insulin levels. To reduce sodium imbalance and uric acid build-up, maintain functions of tissues, reduce the risk of keto flu, and improve performance, it is necessary to consume enough fluids.
Keto Cycling
Keto cycling involves following the keto diet for a certain amount of time and then taking a day (or more) off. “It’s also called carb cycling,” says Molly Devine, RD, the founder of MDS Nutrition in Durham, North Carolina. “That’s another term for it, because there are higher-carb days and lower-carb days.”The idea is to make the keto diet easier to follow. Knowing there’s a day in the near future when you’ll be allowed to eat carbs again might help you stick to the diet for longer.
How Keto Cycling Works
Keto cycling doesn't have a strict definition. Some people choose to have five or six days on keto followed by a day or two off. Others will do keto for 10 to 12 days followed by three to four days off.Devine typically doesn’t recommend taking more than two days off keto. “Several higher carb days in a row almost always lead to ‘falling off the wagon’ and the return of intense carb and sugar cravings for most people,” she says. She says to start with just one day so you can see how your body responds and how quickly you return to ketosis afterward.
When to Try Keto Cycling
Devine says not to jump right into keto cycling. “I would definitely not try keto cycling until you’re about two to three months into your keto diet,” she says. “That's because you need to make sure your body is fat adapted so that it can get back into ketosis easily.” In her practice, Devine has noticed that if the body is used to being in ketosis, it’ll snap back more quickly after eating a carb-heavy meal than if a person is new to keto, though there’s not enough research to confirm that this is always the case.
Potential Benefits of Keto Cycling
Some anecdotal evidence suggests that people are more likely to stick with keto if they incorporate cycling. You could also end up losing more weight if you stick with the diet for a longer period than you otherwise would have.Some people believe elite athletes benefit from keto cycling because their bodies use extra carbohydrates as energy to power through difficult workouts and races. “For an avid athlete, timing carbohydrate intake based on intensity and type of activity can have performance benefits,” Devine says.
Challenges of Keto Cycling
Because it’s best to try keto cycling after your body has already adjusted to ketosis, you likely won’t be able to avoid the challenges of starting keto, such as the keto flu.And while Devine says keto cycling can be helpful for people who crave higher-carb items from time to time, she warns it’s not for everyone.“Anecdotally, some people who try keto cycling do find it difficult,” she says. “When you reintroduce carbohydrates back into your diet - and this is more about refined carbs, I’m not talking about eating an apple - you don’t feel very good.” She says some people experience a so-called carb hangover - the body feels kind of bloated and inflamed, and you may develop headaches.It can also be a challenge not to overindulge on those days off the diet.
Research Findings on Ketogenic Diets and Athletic Performance
Endurance Performance
Phinney demonstrated that 28 days of a KD was a sufficient duration to retool the muscle mitochondria to sustain endurance capacity at moderate intensity. One of the arguments put forward for endurance athletes to consume a KD is humans’ limited stores of carbohydrate (~2200 kcal) versus fat (~30,000 kcal in someone with 7-14% body fat).
However, despite achieving nutritional ketosis and increased lipid oxidation, endurance capacity remained limited by glucose availability. Prior to the commencement of exercise, glycogen stores were reduced by ~45% following a KD. Decreased economy observed at vigorous intensity is noteworthy as it better represents the intensity of competitive endurance athletes.
Endurance performance ranging from 70 to 168 mins in duration was sustained in recreationally trained individuals.
Strength Performance
Current evidence suggests no decrement in maximal strength. A 1RM represents an extreme of the exercise continuum, requiring maximal-force production.
Sprint Performance
No decrement to Wingate, 100 m sprint and 30-15 repeated sprint performance were observed following 3-12-week adaptation, while benefit to SS sprint performance was observed following 12-week adherence within trained and recreationally trained athletes.
Muscle Hypertrophy
For the first 10 weeks of Wilson et al’s investigation, groups experienced similar muscle hypertrophy. In contrast, Vargas et al demonstrated recreationally trained men consuming a non-KD increased lean body mass to a greater extent when compared to a KD group following an 8-week training intervention.
Conclusion
Ultimately, further research needs to be done on the keto diet or high-fat diet and its impact on athletes. However, there is little evidence of improving low-intensity activities and reducing weight. Available knowledge demonstrates no clear performance benefit to athletes following a KD, with some benefit shown mainly in short duration, vigorous-intensity tests, when weight loss was likely a confounding variable. While many of the trials provided no performance benefit, it is important to note that a KD often did not cause a performance decrement, particularly in recreationally trained athletes.