Keto Diet & Running Economy – The Forgotten Factor

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Ketogenic diets hit the mainstream in a big way last year after more than a decade of build-up in athletes in the CrossFit and ultra-endurance scene, and more than 30 years after initial research into the diet. The very low-carb, high-fat keto diet has shown some impressive results in people who are overweight, obese, struggling with type-2 diabetes or metabolic syndrome.(1,2,3) The reduction in carbohydrates in these groups - typically from elimination of processed foods, sugars, desserts and alcohol – results in a significant caloric reduction which is the key underlying principle of all successful weight loss regimes. Keto diets also increase your ability to burn body-fat as a fuel source, and perhaps the most important factor, helps your feel full and satiated for much longer periods throughout the day, new research highlighting this may be due to a reduction in triglycerides crossing the blood brain barrier.(4)

Okay, so keto diet can be a very useful tool for weight loss and improving metabolic health, but what about performance? The internet is loaded with anecdotes about transforming yourself into a ‘fat burning machine’ by shifting to a keto diet, as well as emphasizing to recreational athletes that ‘carbs are for suckers’, implying endurance performance is superior when you follow a keto diet compared to the traditional high carb diet. Are all of these anecdotes correct? Are sport scientists missing out on something? And is there any research to back up these claims? Let’s dig a little deeper and find out.

There is actually very little research on ketogenic diets and endurance performance. The original study on keto diets and performance was done by Stephen Phinney in the early 1980s on five cyclists. Among this group, two cyclists improved their endurance, one saw no change and two cyclists got worse.(5) Not exactly a home run in terms of evidence, however this study was ground-breaking because it showed fat-adapted athletes could burn far more fat (1.5g/min) compared to what had previously thought to be the maximum rate (1.0g/min). It’s an impressive finding. Advocates of a keto strategy for endurance performance highlight the fact that body-fat stores provide a massive fuel source, because even an athlete at 10% body-fat has approximately 30,000 calories of excess energy. Unfortunately, a major shortcoming of Phinney’s study, if you’re trying to win a race, is that cyclists trained at 62-64% of their Vo2max, not exactly a speed that will win a race.

Fast-forward to 2016 and Phinney and colleague Jeff Volek published the FASTER (Fat-Adapted Substrate use in Trained Elite Runners) study in elite ultra-endurance triathletes and runners. The long-term keto adapted athletes (almost 2 years adhering to the diet) were found to burn fat at a high rate (1.2g/min) during a 3-hour submaximal aerobic test at 64% VO2max.(6) Another study in 2016 by Tim Noakes group comparing keto-adapted endurance athletes – following a diet of less than 50g of carbs and 70% fat for over year – were pitted against a group of higher carb athletes in a 2-hour ride at 70% VO2max. Researchers found the keto group did indeed burn more fat (1.2g/min) compared to the high carb group (0.5g/min).(7)

All of this information is really interesting, but it still doesn’t answer the most important question; what happens on race day? When you’re trying to beat the competition, does keto help or hinder an endurance athlete.

Dr. Louise Burke PhD, Head of Sports Nutrition at the Australian Institute of Sport, put this question to the test last year. Her research group took a collection of elite and Olympic race-walkers, adapted them to a ketogenic diet, and simulated a race to examine the impacts on performance.  To date, this is the best study on the impacts of keto diet on endurance performance. Let’s see what they found.

Twenty-one male racewalkers participated in the study at the Australian Institute of Sport (AIS), living in residences where all their meals and training was under strict supervision from the research team. These were not your run of the mill recreational race walkers. They were selected based on their performances and rankings by the IAAF (International Association of Athletics Federation) and made up of 7-time Olympic and World championship medalists to world-ranked juniors.

The study involved three different training groups; a high carb group, a periodized carb group and a keto group. All the participants underwent three weeks of intense training - race walking, lifting, and cross-training (running, cycling, or swimming) – and were tested pre- and post- competition to assess the impact of the three diets on performance.

What did Dr. Burke and her team uncover?

After the three weeks of training, all three groups of racewalkers improved their aerobic fitness regardless of which diet they were on.(8) (Not really surprising, considering they were all in a training camp setting. If they didn’t get fitter, something would really be off piste).

Next, the keto group of racewalkers did exhibit significantly higher rates of fat oxidation during the race walk competition over a wide range of intensities, averaging about 1.5/min.(8) (This is on par with Phinney’s earlier study in the 1980s).

Sounds great, but how did they the keto group perform in the 10km race and 25 km long walk event? In the 10km trial, both the high-carb and periodized-carb group improved their race time, by 6.6 and 5.3% respectively (over their pre-camp testing), following the three-week training camp.(8) Unfortunately for the keto group, their performance was marginally worse during the 10km race (see figure below).

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In the 25km long walk, the keto group showed an increase in heart rate compared the both carb groups who experienced reductions after the long walk. The perceived exertion was also greater in the keto group compared to carbs race walkers.(8)

Why did the low-carb group struggle to perform as well as the carbohydrate fueled racers? Ketogenic diets have a negative impact your running economy.(8) Running economy is how much oxygen you used up at a given running pace. A runner with a superior running economy uses less oxygen at a given speed, which is a reliable metric for who will win a race. In Burke’s study, the fat-adapted elite keto racewalker did burn more fat, but at the expense of a reduce running economy (which means higher oxygen demand) at real-life race intensities. This wasn’t the case for either the high or periodized carb groups. (And don’t forget, the more fat-adapted you are, it comes at the expense of your ability to burn carbs effectively for fuel - pyruvate dehydrogenase enzyme levels fall – which is another performance roadblock).(9)

What does all this mean for you?

If you’re an elite athlete or performance-driven, you need carbs to win on race day. Keto diets reduce running economy (increasing your oxygen demand) as well as increasing heart rate and perceived exertion. At the moment, there just is not enough evidence to support going 100% keto, nobody has beat the competition using this strict dietary strategy. (Even renowned ultra-marathoners in the blogosphere who are “keto” athletes rely primarily on simple carbs when it comes to race day).

Of course, this isn’t a black or white situation. There are definite advantages to training in low-carb states (called low carb availability in the research) during your training blocks to trigger beneficial adaptations in the lead up to competition. Dr. Burke and her team acknowledge this in their research, stating … “a periodized programme that includes some training sessions deliberately undertaken with low… carbohydrate availability (‘train low’) or a delay in replacing muscle glycogen after a session (‘sleep low’) may promote greater cellular adaptations to training and enhance performance to a greater magnitude than undertaking all sessions with high carb availability.” This is a powerful statement.

If you’re a low-carb or keto athlete, it’s effectively saying you can absolutely get benefits by using these approaches during your training block. It can be a great training-nutrition strategy. Just don’t confuse that with your “race-day” nutrition strategy, where carbs are still king.

This doesn’t mean you commit to 100% keto or 100% high carb all of the time. As Dr. Burke highlight in her study… “the quantity and timing of carbohydrate intake should be personalized to the athlete and periodized within the various micro- and macro-cycles of training and competition.”

Just like you wouldn’t train the same way every day of the week, so why do you eat the same way? Regardless if it’s keto or high-carb. (There is a lot of nuance in different fueling strategies, and I’ll get into these in more detail in future blog posts).

Individualizing your carb intake to match your goals is a crucial piece of the puzzle.

Also, take into account your current fitness level and body composition.

If you’re a recreational exerciser training up for a half-marathon or marathon with the aim to lose weight and improve health, yet you’re guzzling back sports drinks every session and seeing not shift in body composition, then your fueling strategy is flawed. Re-assess and adjust accordingly.

Bottom Line: At the end of the day, what are you trying to accomplish? If it’s to win the race or perform your personal best then the research shows race-day nutrition should definitely have carbs (as well as in the 24-hours leading up to the race). If it’s to lose weight and improve metabolic health, and not about your personal best, then you’re fine to err more on the side of low-carb to reap more benefits on the weight loss and health front. But, don’t be afraid to add more carbs on days when training intensity is higher to maximize your adaptations to training.

There is a lot nuance and no single correct answer when it comes to fueling for sport. Just remember to always consider the context of your specific athlete, and their individual goals, when designing the right nutrition strategy for them.

Dr. Marc Bubbs ND, MSc, CISSN, CSCS

Ps. Wonder how exogenous ketone supplements would impact endurance performance? Stay tuned for an upcoming podcast episode on this topic… (Subscribe here!)

 

The Hydration Debate - How Much Water Do You Really Need?

The Hydration Debate - How Much Water Do You Really Need?

As we move into the summer, the competitive season for endurance sports hits full swing. Regardless if you’re an experienced runner or novice, you’ve likely been reminded by your run coach or peers “make sure you drink enough water during your run!”

For years the recommendation from run coaches has been to drink beforeyou are thirsty, to prevent dehydration and subsequent decrements in performance. But if you aren’t racing at the front of the pack, do you need this much water?

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7 Ways Gut Microbiota May Impact Athletic Performance

7 Ways Gut Microbiota May Impact Athletic Performance

Your gut is home to over 100 trillion different microbes that play a synergistic role in your health and performance. The majority of your gut microbiota are made up of bacteria that reside in the colon, however viruses, fungi and protozoa also play key roles.(1) Scientists are still uncovering all the complexities of how these microbiota influence our health, although we do know they help to support vitamin production, the breakdown of fiber and communicate directly with your immune system.

The question for athletes is… “can your gut microbiota impact your athletic performance?” New research suggests it can. Let’s take a quick look at seven potential areas of interest:

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The Athletic Potential of Vitamin D

It’s the middle of winter, and the days are dark and cold. But you’re still training intensely and eating clean to get ready for your upcoming competition. Unfortunately, there is one vitamin no amount of clean eating can fix, especially in athletes. New research suggests maintaining the right levels of vitamin D may improve several elements of performance, including your VO2 max, sprint capacity, and power production.

A Growing Research Field

Exercise dramatically increases an athlete’s demand for vitamin D, as your muscle, heart, and vascular tissue all contain key vitamin D receptors. Today, studies show more than 50 percent of athletes are low in vitamin D.1 While the direct cause isn’t clear, it’s most likely a combination of things like inflammatory processes, muscular damage, increased protein synthesis requirements, increased immune activity, lack of sun exposure, race, and genetics.2

A clear vitamin D deficiency occurs at blood levels less than 20ng/mL (< 50 nmol/L), while insufficiency for athletes is generally defined at blood levels between 20-32 ng/mL (50-80 nmol/L). Insufficiency simply means you’re not getting enough to meet the demands of your activity. Intense training is demanding. New research suggests that 40-50ng/mL (100-125 nmol/L) seems to be the “sweet spot” for supporting optimal athletic performance, and experts agree the body needs daily replenishment to meet that requirement.3,4

Achieving your ideal vitamin D intake may upgrade six key areas of performance:

  1. VO2 max
  2. Muscular power production
  3. Testosterone levels
  4. Inflammation
  5. Susceptibility to colds and flu
  6. Mood

Let’s take a closer look at each.

1. VO2 Max

You likely spend a lot of time planning and periodizing your training to maximize your efforts, but did you know that not having enough vitamin D could compromise your maximal oxygen uptake, or VO2 max, a classic marker for assessing aerobic fitness? New research in professional hockey and soccer players found a strong correlation between low vitamin D status and VO2 max. If you’re a weekend warrior, this relationship may be even stronger.

Experts will tell you just because there is an association doesn’t mean that increasing the amount of vitamin D in your diet will improve performance. However, a new study in vitamin D deficient rowers found that 8 weeks of supplementation (6,000IU per day) resulted in more than a 10 percent improvement of VO2 max. For elite athletes, improving performance by 2-3 percent is the difference between a podium finish and being in the middle of the pack.5,6,7 Remember, more is not always better. Talk to your doctor and get tested before supplementing with high doses of vitamin D.

2. Power Production

Your muscle tissues have many key receptor sites for vitamin D, and they seem to play a key role in supporting power production. For athletes, increasing power production translates to improved performance on the playing field. Recently, the Canadian Women’s National Hockey strength and conditioning team found athletes with higher power production were more likely to make the final selection for the national team. 

Additionally, a study in soccer players found increasing baseline vitamin D status over an 8-week period resulted in an increase in 10-meter sprint times and vertical jump.8 While not all studies found this relationship, it’s important to ensure you meet the minimal baseline requirements to ensure maximum training benefit.

3. Testosterone Levels

Low testosterone is a common symptom in athletes who are over-reaching and overtraining. Unfortunately, too many people look for a quick fix rather than address why their testosterone levels are low in the first place. Vitamin D is a precursor to testosterone production and may increase the binding efficiency of testosterone to its receptors.4 Low levels are linked to increased protein breakdown, reduced strength, and increased body fat.

If you’re an athlete over age sixty, the connection is even more compelling because low vitamin D levels at that age correlate strongly to low testosterone levels.9 A new study over a 12-month time span found that adding approximately 3,000 IU of vitamin D daily resulted in increased total, bioavailable, and free testosterone.10 For those training through the winter, low testosterone combined with intense training will lead to sub-optimal recovery and increased risk of symptoms of overtraining (i.e., increased muscle soreness, low mood, fatigue, low libido, etc.). This is especially true for athletes who compete in indoor sports year round that limit sun exposure.

4. Inflammation

Inflammation is a natural product of intense training. However, too much inflammation can impair muscular function and future performance. One study showed adding an extra 4,000 IU of vitamin D daily can offset the increased inflammatory reaction with a high-volume training load of 10 sets of 10 reps of compound exercises in men and women.11

Interestingly, the group adding extra vitamin D also noted a mere 6 percent drop in power output over the course of the workout, while the group not supplementing had a 32 percent decrease in power. Amazingly, this deficit lasted for up to 48 hours. If you’re preparing for a competition or the CrossFit Games, maintaining power output during competition is critical to your performance.

5. Colds and Flu

There is nothing worse than catching a cold or flu in the days leading up to a competition. All those hard training days and dedication to be at the top of your game, only to be cut short by a nasty bug. If you’re low in vitamin D, the “foot soldier” immune cells that make up your innate immune system will also be low. If this first-line of immune defense is compromised, you’ll be at increased risk of infection.12

Vitamin D promotes hundreds of anti-microbial proteins in the body that fight off bacteria and viruses and helps keep your immune system robust in the build-up to competition. Research in athletic populations highlights that maintaining optimal levels of vitamin D can reduce common infectious illnesses.13 If your levels are low, your immunity and performance will likely be compromised.

6. Mood

Training intensely isn’t just tough on your muscles and joints. It also takes a toll on your mental game. If you're an athlete, you regularly push that fine line between over-reaching (pushing beyond your limits to grow stronger) and overtraining (pushing too far beyond your limits). Therefore, it’s crucial to maintain a positive mood as you fight through the toughest weeks of your training.

Low levels of vitamin D are consistently associated with low mood and depression, and because many athletes train indoors through the winter months (and sometimes even summer, depending on your sport), deficient levels can impair you sense of well-being.14 Cognitive decline also impacts your decision-making abilities, which are crucial in the heat of competition, yet fatigue and pain make them very difficult.

Sources of Vitamin D

Now that you know vitamin D is key for optimal performance, where is the best place to get it? The sun is far and away your best source of vitamin D. Fifteen minutes of exposure on 5 percent of your skin leads to 10,000-20,000 IU of vitamin D production.4 If you live in a city with a true winter – north of the 42nd parallel – you’ll need more than sun exposure alone to meet your demands, as the sun isn’t high enough in the sky for an adequate dose.

Including vitamin D rich foods in your diet should always be your foundation, and the best dietary sources include egg yolks, pork (yes, bacon!), mushrooms, fortified milk, and yogurt (if you struggle to digest dairy effectively, discontinue).

Of course, if you live in a city with a true winter climate, food alone won’t meet your demands. The general recommendation for supplementing with vitamin D during winter is 1,000-2,000 IU per day. However, this is the case for the general population, not athletes. The research on athletes suggests between 4,000-6,000 IU of vitamin D3 daily is a good bet, however this should only be taken during your intense training phases (up to 8-12 weeks), or from November to March. If you decide to take vitamin D doses greater than 2,000 IU, you must get regular blood tests done with your doctor.

Give Yourself a Winning Edge

Whether your goal for 2016 is achieving a new personal best or finishing on top of the podium, make sure your vitamin D levels are adequate. Assess your vitamin D status, add more vitamin D-rich foods, and find the right supplement strategy to meet your needs.

Intense training requires a robust nutrition plan to meet your body’s demands, and failing to adequately replenish vitamin D can negatively impact too many key systems to ignore. Get your daily dose of vitamin D this winter. The research shows it can make all the difference.

(Read the rest of my article @BreakingMuscle)

Dr. Marc Bubbs ND, CISSN, CSCS

 

References

1. Farrokhyar F, et al., “Prevalence of vitamin D inadequacy in athletes: A systematic review and meta-analysis,” Sport Medicine 5 (2014): 365–78.

2. Willis KS, Smith DT, Broughton KS, Larson-Meyer DE. “Vitamin D status and biomarkers of inflmmation in runners,” Journal of Sports Medicine, 3 (2012): 35-42.

3. Ogan D, Pritchett K. “Vitamin D and the athlete: Risks, recommendations, and benefits,” Nutrients 5 (2013): 1856–1868.

4. Dahlquist D et al. “Plausible ergogenic effects of vitamin D on athletic performance and recovery,” Journal of the International Society of Sports Nutrition, 12 (2015):33

5. Koundourakis N et al. “Relation of vitamin D level to maximal oxygen uptake in adults,” American Journal of Cardiology, 107 (2011):1246–9.

6. Forney L, et al. “Vitamin D status, body composition, and fitness measures in college-aged students,” Journal of Strength and Conditioning Research, 28 (2014): 814–24.

7. Jastrz?bski Z. “Effect of vitamin D supplementation on the level of physical fitness and blood parameters of rowers during the 8-week high intensity training,” Facicula Educ Fiz ?i Sport, 2 (2014): 57–67.

8. Close G et al. “Assessment of vitamin D concentration in non-supplemented professional athletes and healthy adults during the winter months in the UK: implications for skeletal muscle function,” Journal of Sports Science, 31 (2013): 344–53.

9. Wehr et al. “Association of vitamin D status with serum androgen levels in men,” Clinical Endocrinology (Oxf), 73 (2010): 243–8.

10. Pilz S, et al. “Effect of vitamin D supplementation on testosterone levels in men,” Hormone and Metabolic Research, 43 (2011): 223–5.

11. Barker T et al. "Supplemental vitamin D enhances the recovery in peak isometric force shortly after intense exercise," Nutr Metab (Lond), 10 (2013): 69.

12. Youssef D et al. “Vitamin D’s potential to reduce the risk of hospital-acquired infections,” Dermatoendocrinol, 4(2012):167-75.

13. Larson E. “Vitamin D supplementation in athletes,” Nestle Nutrition Institute Workshop Series, 75 (2013): 109-21.

14. Polak M et al. “Serum 25-hydroxyvitamin D concentrations and depressive symptoms among young adult men and women,” Nutrients, 6 (2014): 4720–30.