The keto diet, short for ketogenic, is the latest variation of a low carbohydrate diet with a twist that it recommends eating high levels of dietary fats. Claims suggest that this trendy diet can help with weight and improve performance, but dancers should carefully take a deeper look at the metabolic and performance consequences before adopting this diet.
What does “keto” even mean?
A keto diet suggests people eat 70-80 percent of their calories from fats and only 5-10 percent from carbohydrates. By contrast, the American College of Sports Medicine (ACSM) recommends that 25 percent from fats and 55-60 percent of calories come from carbohydrates.
Some of the confusion with these diets comes from a misunderstanding about the positive impact that well chosen carbs have on the body both in performance and weight management. When dietitians talk about carbs as good energy sources, we usually mean fruits, veggies, whole grains, oats, quinoa, beans and peas, not necessarily white flour and cookies. Not all carbohydrate sources are created equal, but they all give the body readily available energy.
In general, the body performs best by creating fuel for hard-working cells by metabolizing ingested carbohydrates, fats and proteins. Dancers also use stored glycogen to fuel activity. However, during a period of starvation, inadequate fuel or very low carbohydrate intake, the body still has to find a way to get energy. In this state, the body metabolizes fatty acids, and the three compounds that are then formed are called ketone bodies. This survival mechanism, called ketosis, helps to ensure that there is some kind of fuel for cells, even if it’s not the most ideal metabolic situation for the body. A keto type diet aims to intentionally put the body in ketosis, which can increase acidosis and potentially result in the loss of sodium and potassium in the urine (among other problems). For athletes, a keto diet requires a three- to four-week period in which the body has to adapt to using fats as energy. This diet isn’t like a light switch that you can just turn on and turn off. Proponents of this diet say that ketosis is a good thing, but your body might be feeling otherwise, and it’s not a natural state to be in for a long period of time.
How can a keto diet affect a dancers performance?
Dancers engage in the type of activity that means we go full out and then pause and then go full out again for a short but intense time. Because of this, we use carbohydrate and stored glycogen as our preferred energy source. While there are studies that may indicate preliminary improvement in athletic performance or at least not a reduction in performance with a keto diet, they often fail to research an athlete who is similar to dancers and don’t conduct the research for a long enough time period to see the long-term dip in performance or weight rebound that will likely occur overtime. For example, a published study on gymnasts that shows this diet to have no reduction on measurements of strength. This study had only eight participants and only had them on the diet for 30 days1. Before we just believe a blog post, or the media’s interpretation of a study, we have to dig a little deeper.
According to Dr. Dan Benardot PhD, DHC, RD, LD, FACSM, dietitian, fellow of the ACSM, former director of the laboratory for elite athlete performance, and internationally renowned expert in sports nutrition, “Keto diets fail to provide the energy substrate most used (carbohydrate) in the high-intensity activity dancers are involved in. This is likely to result in lower glycogen storage (the high-intensity fuel needed by dancers), resulting in reduced performance on subsequent days of dancing (i.e. Wednesday will be worse than Tuesday, Thursday will be worse than Wednesday, etc.)”. We have years of excellent research showing the performance enhancing effects of carefully chosen carbohydrates, therefore forcing the body to switch its energy source from complex carbohydrates to fats, will ultimately short change a dancer in the long term. It’s not that a dancer shouldn’t have any fats in his/her diet. We can’t get stuck in an “all or nothing” mentality. Enjoying dietary sources of fats from avocados, nuts, seeds, olive oil, oil from seeds/ nuts like sunflower oil or walnut oil, for example, is healthy and completely fine, even for dancers thinking about their weight.
Can a keto diet help with weight management or fat loss?
Proponents of the keto diet claim that by eating mostly fat, this approach leads to decrease in body fat mass because the diet “burns more fat”. However, this short-sighted view doesn’t fully take into account several metabolic facts. A keto diet, like many low-carb diets, intends to put the body in a state of negative energy balance, meaning that the person is simply eating fewer calories than they are using. In the short term, weight loss is achieved. In my experience working with dancers, I’ve seen some go to very low calorie extremes with these types of fad diets, which backfires with low energy levels, increased risk for injury and long-term fat gain because the body adapts to the restricted calorie level. According to Dr. Benardot, “Adaptive thermogenesis (i.e. the body’s adaptation to an inadequate energy intake) often takes six months or longer. Studies that fail to go this long often miss the rebound weight that is often an inevitable by-product of low-calorie diets.” Think about it. How many people do you know who have done a fad diet (probably low-carb) ended up gaining weight or gaining body fat percentage after a year or so?
The best way to manage weight over the long-term is to limit refined sugar, soda and junk food, and instead fill up on high fibre, nutrient-rich foods like whole (minimally processed) grains, oats, quinoa, beans, peas, seeds, nuts, fruits and vegetables, all of which have carbs and support long-term health. With these as a dietary foundation, dancers can add two to three servings of fats and additional protein if needed. An eating pattern of smaller but more frequent meals/snacks regularly throughout the day is also key. “Weight loss is the wrong metric when assessing the success of a diet. The appropriate metric is fat loss. The lower caloric intake of ketogenic diets is likely to lower both lean and fat mass. Weight is lost, but so is the strength-to-weight ratio, making dancing more difficult. Studies demonstrating the success of a diet should measure fat loss and lean maintenance,” states Benardot. Meaning that if dancers want to be strong, have well-defined muscles, and have relatively low body fat, a restricted, fasting, keto or low carb type diet is not the way to achieve that.
What are the long-term consequences of a high fat/low carb diet?
Fans of this diet suggest it can be eaten indefinitely, but what about heart health? With heart disease being the number one killer in the western world, this is not a small consideration. Any diet that suggests that bacon and butter are okay but lentils and bananas are not is problematic from the start. Research on the longest living people on Earth in the Blue Zones shows that their diets are often up to 70 percent total calories from carbohydrates2.
Benardot warns that a keto diet’s metabolic consequences go beyond just weight management problems. “Keto diets require that a substantial amount of protein be used to satisfy energy needs. This requires that protein be denitrogenated, resulting in higher blood urea nitrogen (BUN), which is toxic and must be excreted. This puts a great deal of pressure on the kidneys to excrete more urea (nitrogen), resulting in greater urine production and greater risk of dehydration.” Dehydration is especially problematic in dancers since it begins with fatigue and impaired balance and gets worse from there.
Another problem with low carb/high fat and low carb/high protein diets is reduced bone mineral density and increased risk for stress fractures. Benardot warns, “The urea which is formed, and must be excreted, is acidic. The kidneys retain more serum ionized calcium to neutralize this acidity, but because this could increase serum acidity (potentially dangerous), calcium is taken from bones to replace the serum calcium lost in the urine. This lowers bone mineral density and increases the risk of stress fractures.”
Since stress fractures are such a common injury in dancers, this is yet another reason why a keto diet isn’t right for our field. Plus, beans, greens and low-fat dairy are important sources of calcium, and they aren’t a significant part of a keto diet.
Special thanks to Dr. Dan Benardot for his contributions to this article. Find him at www.foodandsport.com.
- Paoli A, et al. Ketogenic diet does not affect strength performance in elite artistic gymnasts. J international society of sports nutrition. 2012 jissn.biomedcentral.com/articles/10.1186/1550-2783-9-34
- The Blue Zones. www.bluezones.com
By Emily C. Harrison MS, RD, LD of Nutrition for Great Performances.
Emily Cook Harrison MS, RD, LD
Emily is a registered dietitian and holds both a bachelor’s and master’s degree in nutrition from Georgia State University, USA. Her master’s thesis research was on elite level ballet dancers and nutrition and she has experience providing nutrition services for weight management, sports nutrition, disordered eating, disease prevention, and food allergies. Emily was a professional dancer for eleven years with the Atlanta Ballet and several other companies. She is a dance educator and the mother of two young children. She now runs the Centre for Dance Nutrition and Healthy Lifestyles. She can be reached at firstname.lastname@example.org