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Is the Paleo Diet Good for Runners?

The diet is praised for its benefits, but how helpful is it for endurance athletes?

Pre-race pasta feeds—with piles of pale noodles and white bread in quantities that would be frowned upon elsewhere—have been customary for long-distance runners since the 1960s. While the carb-laden diet endures, the growing popularity of the Paleo Diet has caused many runners to wonder if they might benefit from going primal. Some Paleo principles overlap with those taught by sports nutritionists for years, but the controversy over carbohydrates has created some confusion among runners.

Paleo Basics

The Paleo Diet is based on what advocates have identified as the diet of our hunter-gatherer ancestors who existed before the Neolithic agricultural revolution. The majority of the diet comprises grass-produced meats, fish, fruits and veggies, eggs, nuts and seeds. Grains, legumes, dairy, refined sugar and salt are off limits. Put simply, going Paleo is all about taking in plenty of protein and healthy fats, with fewer carbohydrates, which are derived from fruits and vegetables.

Primal converts among the general population report a long list of benefits from the diet, including weight loss, fewer spikes in blood sugar and insulin levels, improved appetite control and a decrease in cardiovascular risk factors among Type 2 diabetics. Dr. Loren Cordain, author of The Paleo Diet, says it’s all about packing in as many nutrient-rich foods as possible.

“Whole grains are much less nutritionally dense in the 13 vitamins and minerals most lacking in the U.S. diet,” he says. “Accordingly, their inclusion in our diets displaces more healthful fresh fruits, vegetables, meats, fish, seafood, poultry and eggs and dilutes the overall nutrient density of our diets.”

When it comes to runners, Cordain says there are several reasons the Paleo Diet benefits endurance performance. First, thanks to lean meats and fish, it is high in branched-chain amino acids, which aids in muscle repair. As a result of the high amount of fruits and vegetables, the caveman approach is said to help prevent muscle loss as well. What’s more, these fruits, veggies and lean meats offer important sources of antioxidant vitamins, minerals and phytochemicals, making for a healthier immune system and fewer colds and illnesses.

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Many Paleo converts also point to the diet’s ability to train your body to learn to burn fat more efficiently. Since your main energy sources are fat and carbohydrates, the former being in great supply and the latter being limited, intuitively it makes sense to increase a long distance runner’s reliance on fats before accessing the small amount of carbs stored in the muscles as glycogen.

With that said, the latest research that looked at the effect of “training low,” that is training with low glycogen stores as a result of limited carb intake, didn’t bear out any benefit when it came to athletic performance. The author of the scientific review, Louise Burke of the Australian Institute of Sports, writes, “Despite increasing the muscle adaptive response and reducing the reliance on carbohydrate utilization during exercise, there is no clear evidence that these strategies enhance exercise performance.”

Carb Controversy

The main question is: How many carbohydrates should be included in our diets? What works for the average joe won’t work for a distance runner. This is why sports nutritionists have long been recommending that a runner’s diet incorporates 60 percent carbohydrates.

When you eat carbohydrates, they break down into several sugars, one of which is glucose, which is then stored as glycogen in the liver and muscles and provides critical fuel for muscles. High stores of glycogen have been shown to increase an athlete’s time before exhaustion and improve performance. While your body burns both fat and carbohydrates up to a certain intensity level, it eventually relies almost exclusively on glycogen.

“The research shows if you put people on low-carb diets for an extended period of time, they can exercise at about 50 percent VO2 max, so they could finish a marathon, but there’s no way you could sustain 70 to 80 percent VO2 max,” says Dr. Michael Joyner, a physician-researcher and leading expert on physical performance and exercise physiology.

Nancy Clark, a registered dietitian and sports nutritionist in the Boston area, as well as the author of Nancy Clark’s Sports Nutrition Guidebook, says that while the Paleo approach is good because it gets people eating more natural and less processed foods, a runner loses important sources of nutrients when they cut out grains and dairy.

“Some people think carbo-loading means stuffing themselves with pasta, but to me it means eating mostly quality whole grains, veggies and fruits to load your muscles,” she says. “If a person is eliminating foods, they can get nutrients from alternate sources, but it’s a lot of work: In terms of carbs, you need three cups of blueberries to replace a bagel.”

If you are training and racing in a carbohydrate-depleted state, not only are your muscles under-fueled, but your brain also is, which is what causes runners to hit the wall.

“You have a limited amount of muscle and liver glycogen and when your blood glucose drops, many runners get that bonking sensation,” Joyner says.

Keri Glassman, a certified dietitian and nationally recognized nutrition expert and author based in New York City, echoes that point: “You need to create that big gas tank of glycogen and you top off that gas tank through your diet so you don’t hit the wall.”

Modified Paleo

Since carbohydrates are non-negotiable for endurance athletes, Cordain co-authored The Paleo Diet for Athletes with Joe Friel, a renowned coach with a master’s degree in exercise science. A refinement of Cordain’s original Paleo Diet, this regimen allows for the consumption of carbohydrates and simple sugars immediately before, during and after exercise that exceeds an hour.

In particular, they suggest bananas, sweet potatoes, regular potatoes and yams as good sources. This also means that a runner following a modified Paleo Diet may have to consume some of the so-called “non-optimal” foods that are glucose-rich, such as sports drinks, gels, bagels, pasta, bread and rice, but the total carb intake is still less than the long-recommended 60 percent.

“I think a very healthy diet is close to Paleo,” Glassman explains. “I always say I like Paleo plus ancient grains or Paleo plus yogurt.”

Barring any nutritional restrictions, runners who are already consuming plenty of veggies, fruits, whole grains, leans meats and dairy aren’t likely to benefit from a strict Paleo Diet. For those who are subsisting off of highly processed grains and piles of refined sugars, the structure that going primal provides may have some benefits, as long as they include enough carbohydrates.

The amount of carbohydrates you need comes down to the type of running you’re doing. Put simply, pace and distance matter. The faster the pace and the longer the distance, the more your body relies on those glycogen stores. “If people want to do some intense exercise, they need some carbs, and if they want to do a lot of it, they need a lot of carbs,” Joyner explains.

There are isolated examples of athletes subscribing to Paleo, low-carb diets and still running well, like Timothy Olson, who won the 2012 and 2013 Western States 100-Mile Endurance Run. For most, anything but short, slow runs are going to require a bit more carbs in the tank.

Perhaps the most important point is that there is no such thing as a one-size-fits-all diet. Lactose intolerance, gluten allergies and other factors, such as training load, workout intensity, metabolic needs and personal ethical concerns surrounding vegan and vegetarian lifestyles, all dictate what you should be putting on your plate. In weighing the benefits and drawbacks, it seems many runners will find themselves as neither a primal convert, nor a processed-carb hound.