While a low-carb Paleo diet is phenomenal for supporting weight loss and improving health if you are overweight, out of shape, or obese, not everyone is trying to lose weight.
For athletes training to achieve a personal best running a 10k, triathlon, or qualifying for the CrossFit Games, your eating strategy will not be one in the same.
Exercise is a catabolic process, triggering a release of stress hormones cortisol and adrenaline in order to raise blood sugars to fuel your activity. If you are exercising at a slow pace (less than 65% heart rate) your body has the time to use fat as a primary fuel source. However, as your exercise intensity increases your body quickly shifts to using muscle and liver glycogen (your body’s carb stores) to fuel exercise.
You have a limited capacity to store glycogen, which means after about 1-hour of training at a high intensity, you’ll likely have exhausted all your body’s glycogen stores.
WHAT’S THE MATTER WITH LOW GLYCOGEN STORES?
The research is quite clear that if you start your next training session with low or sub-optimal glycogen status, you’ll significantly reduce your capacity to work and your performance will suffer. A recent study of athletes who consumed only 40% of their total calories as carbohydrates and performed “two-a-day” training sessions suffered a significant decrease in their performance during the 2nd session because they did NOT adequately replenish muscle glycogen stores.1
If you are training at high intensity and following a low-carb diet, you are treading a fine line. If your goal is to be fit and lean, this isn’t really a problem. However, if your goal is optimizing your performance potential, eventually you will exhibit signs of overtraining and exhaustion.
Overtraining happens when you train intensely for too long, without adequate rest periods or tapers built into your training regime. While you do want to push yourself to the edge to stimulate a training adaptation (‘over-reaching’), you don’t want to push yourself over the edge!
Short-term symptoms of inadequate glycogen repletion include fatigue, reduced work capacity during training, poor recovery and extended delayed onset muscle soreness (DOMS). Long-term symptoms are pronounced fatigue, reduced strength levels and increased muscular weakness.
HOW CAN A PALEO DIET HELP IMPROVE RECOVERY AFTER EXERCISE?
The best way to replenish glycogen after training is to consume high-glycemic index (GI) carbs. High GI carbs enter the bloodstream quickly, allowing you to rapidly replenish glycogen stores in the first 30-60 minutes after training, when glycogen synthase enzyme activity is elevated and allows for optimal replenishment.2 Root vegetables make a great post-workout carb choice, especially if you bake them, which naturally raises the glycemic index of these foods, such as sweet potatoes, yams, yucca, plantains, carrots, beets, parsnips, etc.
If you are on the go and don’t have time to sit down for meal, try adding some dried fruit to your post-workout nutritional arsenal. Dried fruit is very high-glycemic, and while not ideal as a midday snack when sitting at your desk, it’s a great option after vigorous activity. Try 2-4 Medjool dates for 36-72g of carbs, or half a pack of dried mangos (1.5oz provides 36g of carbs).
The total amount of carbs you consume post-training depends on a few variables: your genetics, current body-fat percentage, training phase, etc. Aim for one gram of carbs per kilogram bodyweight in the first hour after exercise (divide your bodyweight in pounds by 2.2 to achieve your weight in kilograms).2,3 This can be repeated every two hours for up to 6 hours post-training for elite level trainees and sports that require two-a-day training, such as triathletes, Olympic weightlifters, and Ironman competitors.
In China, a recent study examined the effects of high-glycemic meals after exercise on performance in runners. The results showed athletes consuming high-GI meals post-training had significantly improved work capacity during their subsequent run four hours later.4 This highlights the importance for refilling your glycogen stores and ensuring your best performance in your next training session or race day.
WHAT HAPPENS IF YOU WAIT TO CONSUME YOUR CARBS POST-TRAINING?
Carbs directly replenish glycogen stores and after exercise your capacity to soak up carbs and top up glycogen is heightened. Research shows that if you wait several hours post-training you will reduce your glycogen repletion rate by as much as 50%!5 Not consuming enough carbs after exercise can also exacerbate inflammation, depress immunity, and lead to prolonged muscle soreness.6
If you’re already following a low-carb (LC) or very low-carb ketogenic (VLCK) diet you can still benefit by incorporating more carbs than normal post-training, without affecting your capacity to burn fat.7 For some, this may be the added boost you need to upgrade your performance. However, at higher intensity exercise the research shows a LC or VLCK diet does not likely support better performance.8
Remember, if you’re gearing up for a 10k run, triathlon, CrossFit Games or your competitive season, fatigue is directly related to muscle glycogen depletion when exercising at higher intensities. For optimal athletic performance, refuel with the right amount of carbs post-exercise and take your game to the next level.
1. Ivy JL et al. Muscle glycogen storage after different amounts of carbohydrate ingestion. J Appl Physiol. 1988 Nov;65(5):2018-23.
2. Jentjens R, Jeukendrup A. Determinants of post-exercise glycogen synthesis during short-term recovery. Sports Med. 2003;33(2):117-44.
3. Ivy JL1.Glycogen resynthesis after exercise: effect of carbohydrate intake. Int J Sports Med. 1998 Jun;19 Suppl 2:S142-5.
4. Wong SH et al. Effect of glycemic index meals on recovery and subsequent endurance capacity. Int J Sports Med. 2009 Dec;30(12):898-905.
5. Jentjens R, Jeukendrup A. Determinants of post-exercise glycogen synthesis during short-term recovery. Sports Med. 2003;33(2):117-44.
6. Flakell PJ et al. Postexercise protein supplementation improves health and muscle soreness during basic military training in Marine recruits. J Appl Physiol 2004;96:951-956.
7. Burke LM, Hawley JA, Angus DJ, et al. Adaptations to short-term high-fat diet persist during exercise despite high carbohydrate availability. Med Sci Sports Exerc 20002;34:83-91.
8. Antonio J, Kalman D, Stout S, et al. Essentials of Sports Nutrition and Supplements. International Society of Sports Nutritionists. Humana Press, NY 2008.