Everyone has learned again and again that a balanced diet is key to optimal nutrition, yet there are a lot of “fad” diets, bundles of mixed information on the internet personal opinions and anecdotal success stories about the best methods of eating. Whether it’s low carb diets, juice cleansing, gluten-free, or any other “quick fix”, there are definitely pros and cons with each one. The research behind different diet methods and their results can be mixed, and the conclusions are often skewed to promote nutrition products for the companies that may be funding the research. The most challenging part of navigating all the research and information, especially for athletes, is figuring out how to apply it to individual nutrition needs.
When fueling our bodies, taking anything to an extreme lends itself to creating a nutritional deficiency somewhere else. Numerous macro- and micronutrients work together to make our tissues, hormones, physiological systems, etc. function properly. The importance of balance and consistency in our food patterns applies to athletes especially as nutrition directly affects performance in training and competition. The purpose of this article is to look at the science behind the ketogenic diet (KD) and propose an applicable and balanced nutrition plan, a modified ketogenic diet, for endurance athletes based on individual needs, racing, and overall long-term health.
In the preceding article “Reviewing research aspects of the ketogenic diet on endurance athlete performance: should I try it out?” Loulika Lili-Wiliams, PhD, accurately defines the KD as a high-fat, low carbohydrate and protein sufficient diet. KDs have traditionally been used by dietitians and doctors in clinical settings to treat neurological disorders and errors in metabolism such as diabetes. Eating more fat than carbohydrates stimulates the body to oxidize fatty acids and use ketone bodies for energy. Thus, putting the body in a state of ketosis. As Dr. Lili-Williams summarizes from current research studies, the metabolic benefits to endurance athletes may include increased ATP and mitochondria production, efficient fatty acid oxidation, and maybe VO2 max increase. These are all desirable adaptations, but there are also studies showing that KD methods may lead to dehydration hypoglycemia, and decreased ability to maintain anaerobic workload.
Fat provides energy at an endurance pace, which is low to moderate intensity exercise (i.e., jogging, easy cycling), in which we burn about 50% carbohydrates and 50% fats. As the intensity increases, we utilize more and more carbohydrates, up to 100%. Above that percent our bodies can no longer use carbohydrates for fuel, so lactic acid is generated as a bi-product of metabolism. This is considered the anaerobic zone, which typically only lasts ~15 seconds, then it’s back to carbs and fats for fuel (see figure below).
Carbohydrates (CHO) are the body’s preferred energy source during exercise. Dietary CHO (grains, fruit, starchy veggies, juice and sport drinks) are processed then stored in the liver and muscles as glycogen. During exercise, these glycogen stores fuel our working muscles. How soon we run out of energy from glycogen depends on our workout intensity, so hard and intense workouts deplete glycogen stores more quickly than moderate exercise bouts. Our glycogen stores are limited, so during exercise lasting more than 60-90 minutes, consuming carbohydrates while exercising improves performance. More specifically, 30-60g of CHO per hour will help keep you fueled and feeling strong. This is where specific nutrition information is important for athletes.
In our diet, the standard recommendation for endurance athletes is 50-65% of total calories from carbohydrates. That means the KD, which can be 65% or more of total caloric intake from fat, is a huge deviation from that. This is where it is important to look at the individual athlete to determine what the ratios of carbohydrate/protein should be, because every BODY is different. Not only do intensity and duration of workout determine macronutrient needs, but macronutrient percentages that work for some may be totally different for another depending on age, gender, fitness level, metabolic rate, training/racing calendar, and genetics.
Based on the food science discussed so far, the question becomes whether or not the KD is the best option for endurance athletes, especially because macronutrient needs can differ on a day-to day basis. It seems logical that sparing carbohydrates to promote fat burning could be ideal, and there is some validity to this, but we must look at each athlete as an individual. An athlete that does ultra-endurance activities, where he/she trains and competes for long hours at low intensity may benefit more from a KD than an athlete that needs high end power for sprints and short duration intensity. As stated earlier in this discussion, long sustained efforts utilize more fatty acids for fuel whereas short intense efforts rely almost solely on carbohydrates.
A modified KD, as presented in this paper, is an attempt to find the best method to appropriately fuel an endurance athlete, with the mindset that we put the proper gas in our fuel tank to make our body’s engine achieve optimal results. As stated above, sport nutrition research shows that athletes need 50-65% of their total calories to come from carbohydrates in order to have enough energy (glycogen) available for working muscles. Based on this information as well as the KD benefits, endurance athletes should do well on a 50/35/15 percent CHO/fat/protein ratio. That would be the lowest one could go in carbohydrates and protein but still get the positive ketogenic effects of utilizing fats, sparing carbs, and running that engine all day. As an athlete’s training or racing period changes, such as the duration decreasing and intensity of anaerobic efforts increasing, the KD could be adjusted to 55:30:15, 60:25:15, or 65:25:10 percent’s, respectively. This way, basing the diet plan on what the individual is doing will lend itself to optimal performance as well as long-term health.
The type of fats we choose is important. Fat can be broken into two categories: saturated and unsaturated. Saturated fats are usually solid at room temperature, and lead to high cholesterol and heart disease. We want to limit saturated fats to < 10% of total fat consumption per day. Saturated fats are mostly found in animal products (meat, dairy, egg yolk), processed foods (cookies, baked goods, butter), and all trans fats, even coconut oil. Unsaturated fats are the ones we want to consume. Mono and poly unsaturated fats are fluid at room temperature (Omega-3 fatty acids are the most important in this group, as they are nature’s anti-inflammatories). Food examples include fatty fish and plant sources such as nuts, flaxseeds, avocado, and vegetable oils (canola, olive, peanut, sesame oils, etc.). Keep in mind that fat goes further than carbs or protein, (1 gram of fat has 9 calories, while carbohydrates and proteins each have 4 calories per gram). So, using fat as a sprinkle for flavor to our meals and snacks can go a long way in our total caloric need each day.
When implementing the modified KD for YOUR specific needs and exercise output, be sure to choose LEAN meat and limit red meat consumption. When choosing dairy products, opt for skim or 1% because low to no fat is all you need. The nutrients are in the milk, not the fat. Milk alternatives (almond, soy, rice, etc.) are great substitutes with all the calcium and nutrition you need. Be sure to favor fresh, whole, UNPROCESSED foods. Reconsider getting “fast” food, as it is traditionally low quality, and high in saturated fat, especially prior to training or competition. Instead, favor carbohydrates with low to moderate amounts of healthy fats. Fat takes longer to digest than carbohydrates, so pre workout meals should be low in fat content so you are ready to roll. Also, recovery nutrition should be appropriate for the exercise performed, meaning mainly carbohydrates to replace glycogen to the muscles and moderate amounts of protein to repair tissues. Be sure to get the fats you need in the meals NOT immediately surrounding training or competition, so they have time to digest and the body can efficiently break them down to use as fuel.
In conclusion, the KD can have many positive effects on endurance athletes, but there are upsets to other systems that may lead to detriments as well. Because the human body is a multifaceted and complex set of energy systems, hormones, and metabolic pathways, it is crucial that athletes strive to maintain balance. The ultimate goal should be to find consistent healthy habits so that performance can improve and the body adapt to places where the changes stick. A quick body change is likely in response to drastic food change, and odds are that it won’t last long anyway. Many of us know the post-diet rebounds of gaining it all back, fluctuations of energy levels, or going back to our body’s “normal” appearance. There are tests available to determine the substrate usage at a given workout intensity. These tests can be done to determine if the carbohydrate/fat ratio shifted at given endurance effort. Using the proposed modified ketogenic diet may offer some benefit to a very specific group of athletes racing and training in long aerobic endurance events.