Should Endurance Athletes Switch to a Low Carbohydrate Diet?

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High carbohydrate pasta with tomatoes
Pasta – a typical meal for endurance athletes.

Should endurance athletes trade in their high carbohydrate gels, gummies, and pasta for fatty steak and butter?  A recent study found elite ultra-marathoners and iron distance triathletes on a low carbohydrate diet  burned significantly more fat while running than  their counterparts on a typical higher carbohydrate diet. There was no difference in the level of glycogen depletion between groups after a 3-hour run.

Why Carbohydrates Matter

For several decades endurance athletes have relied on a carbohydrate rich diet to fuel their training and performance. Carbohydrates are the primary source of energy used during activity. They’re also a fast fuel – your body can use gels, gummies and sports drinks very quickly while also accessing the carbohydrates stored in your muscle when your energy needs outpace how quickly you can squirt more gel in your mouth. Regular intake of carbohydrates during  prolonged activity provides an important source of energy for working muscles and helps spare dipping into your reserves in muscle tissue (in the form of glycogen). Once glycogen levels start getting too low, your performance will subsequently decline.

If carbohydrates are important for performance why would anyone go on a low carbohydrate diet?

The longer you run, bike, swim or exercise in general, the more carbohydrates you need to keep up with energy demands. There are three main reasons athletes (particularly ultra endurance athletes) want an approach that doesn’t require carbohydrate during long bouts of exercise are:

  1. Your taste buds get tired –  Eat any food over and over again and you will get sick of it eventually. Now imagine running 30, 50 or 100 miles and eating a gel every 30 minutes. The consistency, sweetness and flavors will make your taste buds revolt.
  2. Your stomach might get upset. Exercise + eating (even seemingly easy to digest carbohydrate products) can cause stomach upset in some people.
  3. You are trying to lose body fat. If you are exercising for long periods of time it may sound counterintuitive to consume 30-60 grams of carbohydrate (or 90+ depending on the type of carbohydrate, your stomach’s tolerance and the type of exercise you’re doing) each hour while training.

If any of these apply to you, a diet that doesn’t force your body to rely on carbohydrates for energy may sound very appealing.

The Study & the Low Carb Diets for Endurance Athletes

The body has amazing ability to adapt to changes in the macronutrient composition of your diet.  In other words, if you eat more fat you’ll burn more fat. If you are adapted to a low carbohydrate diet, you will rely on your body fat for fuel and will not need to consume gels, gummies or any other carbohydrates while running, biking or swimming. However, there is an adaptation period.  It takes time for your body to switch over from relying on carbohydrate to fuel activity to using primarily fat. The study subjects included elite male ultra-endurance athletes who habitually consumed a high carbohydrate diet (> 55% of calories from carbohydrate) and a separate group of those habitually consuming  a low carbohydrate diet (< 20% of calories from carbohydrate and > 60% from fat though the average was 70% from fat) for at least 9 months. Both groups slept, reported to the lab fasted and then drank a 343 calorie shake (the shake contained 4.3 grams of carbohydrate for the low carbohydrate group and  42.7 g of carbohydrate for the high carbohydrate group). Ninety minutes later they ran on a treadmill.

Results

As expected, the low carbohydrate high-fat diet group used a lot more fat when jogging then the high carbohydrate group (88% of calories from fat vs. 56% in the high carbohydrate group). They also used more fat at a higher intensity than the high carbohydrate diet group. They were able to use fat at a good rate – fat is typically a slow source of energy but the rate of fat use in this fat-adapted group was pretty compatible to the typical rate (but not the maximum) at which an athlete can use carbohydrates. Glycogen levels at rest, glycogen breakdown during exercise and re-synthesis after exercise was the same in both groups. * There was no difference in the amount of calories burned between the two groups.

Is This Diet Right for You?

Ultra endurance athletes can adapt to and train on a higher fat diet.  They can also do this without glycogen depletion – glycogen depletion can come with other negative consequences including potential suppression of immune system functioning.  At this time, we do not know if regularly following a lower carbohydrate diet = better endurance performance.

What you need to consider:

  • According to this study you will not burn more calories during exercise when on a low carbohydrate, high fat diet. ** See note below.
  • Your body needs at least 1 month to adjust. The first week will probably suck (you’ll feel terrible and have low energy).
  • You might not improve performance (we don’t know).
  • Can you stay on a low carbohydrate, high fat diet? Do milkshakes made of  heavy cream, olive oil, walnut oil and whey protein sound yummy? Is this diet practical for your lifestyle? If you answer yes to those 2 questions,  then it might be worth a shot. Work with a nutrition expert to ensure you are getting all of the fiber, vitamins, and minerals you need for performance and health.

* Keep in mind the results from this study are specific to endurance athletes.

** If weight loss is your goal, it makes no difference if you burn more fat during exercise if you aren’t burning more total calories in that exercise session. The only caveat here is if a low carb diet means you consume few to no calories during exercise. In this scenario, a low-carb diet may help you consume fewer total daily calories.

Pre-Workout and Post-Workout Meal Ideas

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You’ve seen them. The people who faithfully go to the gym day after day and spend quality time on the cardio equipment and in the weight room. Yet their bodies never seem to make any visible changes. They are training. But they aren’t training smart with a plan that is specifically designed to meet their goals, lifestyle and current state of conditioning. A plan that helps them progress and not just maintain. But, even with the best training program, a person’s progress will be limited if they don’t eat a diet that provides the energy they need while also facilitating training adaptations and helping improve recovery. And though eating well means choosing nutrient-dense foods 90 – 95% of the time, the most important meals for an athlete are pre- and post-workout:

Pre-workout:

In order to sustain your energy levels through your workouts, your body needs food. If you have just 2 hours before you hit the gym, track or field, opt for a lighter snack. Four hours beforehand, opt for meal that is higher in carbohydrate, contains some protein for staying power and is low in fiber and fat (both slow digestion and who wants their stomach busy digesting food when they are about to run sprints?). Lastly, don’t try something new before workouts that may make you a little queasy. For example, spicy food can give you heartburn and greasy food may make you sick to your stomach. Think familiar and easy-to-digest.

Half a cantaloupe with cottage cheese

Snack examples:

  • Cottage cheese and fruit
  • Banana spread lightly with almond butter or peanut butter
  • Yogurt
  • Granola bar
  • Pancakes or waffles

Post-workout:

The main purpose of eating after you workout is to turn a catabolic environment into an anabolic one. In other words – your post-workout meal will facilitate the processes underlying muscle growth, re-hydrate, help curb excess inflammation and restore muscle glycogen. In addition to improving recovery, your post workout meal will help you make training gains.

Post-workout meal ideas:

  • Protein pancakes (Simply pancake mix with added protein powder.)
  • Protein shake
  • Low fat chocolate milk (you’ll need more protein than this if you are lifting weights)
  • Bagel, bread or pita with melted cheese
  • Tunafish or turkey sandwich

Eat so you can train well, don’t hit the gym or run a few extra miles as an excuse to eat more food that doesn’t fit in your training program.

Written by: Rachel Rosenthal & Marie Spano

Sleep – a Critical Component to Sports Performance

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Years ago hitting the gym and throwing around some steel was considered the most critical aspect of sports performance training. However, in more recent years a more comprehensive model of performance has developed based on decades of research on nutrition, sleep, psychology and several other critical components of an athlete’s training regimen. As a sports dietitian with an Exercise Science degree and CSCS, I focus mainly on food & supplements though I sometimes discuss training. But lately I’ve found that I’m also talking about the importance of sleep with my athletes. This topic comes up once I realize they are too tired to plan and prepare their food. Days of sleep deprivation also leads to poor food choices. If an athlete is tired and hungry, caring about good nutrition will be thrown on the back burner while finding food fast becomes the main priority. Quick and cheap turns into a double cheeseburger with fries. And, aside from failing to implement all aspects of their nutrition plan, skimping on sleep also interferes with an athlete’s training and performance. Studies show chronic sleep deprivation leads to:

  • decreased sub max and maximal lifts in the weight room
  • delayed visual and auditory reaction time
  • slowed decision making
  • impaired motor functioning
  • reduced endurance
  • increased fatigue, decreased energy
  • exercise feels harder than it normally is (increased rating of perceived exertion)
  • less efficient glucose metabolism
  • reduced leptin and increased ghrelin
  • decreased growth hormone secretion
  • increased risk of injury
  • elevated cortisol levels which may interfere with tissue repair and growth
  • impaired insulin sensitivity in fat cells = more fat in your bloodstream (over time this may contribute to obesity, Type 2 diabetes and cardiovascular disease).
  • decreased production of leptin, a protein produced in fat cells that tells your brain you have enough energy (fat) stored away so there’s no need to gorge yourself on food. Low leptin = you get hungry and eat.

According to research presented by Cheri Mah,a Stanford University sleep expert:

  • one night without sleep is the equivalent of being legally intoxicated
  • 4-5 hours of sleep for 4 days = 24 hours awake = legally intoxicated
  • 4-5 hours for 10 days = 48 hours awake

Mah’s 8 Strategies to Improve Sleep and Recovery:

  1. Adults should aim for 7-9 hours of sleep. Athletes need 8-10 hours of sleep (and getting in bed at 10 and waking up at 6 doesn’t mean you are getting a full 8 hours since it takes a while to actually fall asleep).
  2. Establish a consistent sleep schedule.
  3. Sleep like a caveman. It should be dark, quiet and cool. All electronics should be off and silent (or program in numbers for emergency calls only and set your phone for these emergency calls). All small lights on electronics should be covered up as these can interfere with sound sleep.
  4. Adults should only sleep when tired. If unable to sleep after 45 minutes, it is wise to get up and do a non-stimulating activity for 15 minutes (reading) then return to bed.
  5. Establish a 20-30 min routine before bed that includes non-stimulating activity. No computers, TVs or video games.
  6. Refrain from alcohol which impairs your sleep quality and fragments sleep preventing the deep sleep that is so critical for recovery (this is why people complain of being exhausted the day after they drink).
  7. Avoid heavy food, any foods that could cause heartburn, spicy foods etc.
  8. Take 20-30 minute power naps and pre-game naps (unless these interfere with the ability to sleep at night). Mah has found this improved alertness by 54%, improved performance by 34%

Matthew Edlund, M.D. takes it even further with the notion of morning people performing better during the day, night owls performing better at night, and both having to combat jet lag (each 1 hour time zone change takes a person 1 day to adjust; this is why West Coast teams beat East Coast NFL teams on Monday Nights). Check out Edlund’s article here. Sleep affects several aspects of training and performance (as well as body weight). Any athlete who wants to feel their best and reach peak performance should take a comprehensive approach to training which includes sound sleep habits.