Feeling Lethargic? Check Your Carb and Fiber Intake

Chelsea LittleAugust 13, 2015
A scene from the start of the 2015 Uitslagen Ladiesrun in Rotterdam. (Photo: Wikimedia Commons)
A scene from the start of the 2015 Uitslagen Ladiesrun in Rotterdam. A recent study published in the Scandinavian Journal of Medicine & Science in Sports is shedding light on low energy availability and eating habits of competitive female athletes. (Photo: Wikimedia Commons)

We have written before about the prevalence of eating disorders in female athletes, but a new study attempts to describe the diets of female endurance athletes who have low energy availability and/or skipped periods.

What is energy availability? It is the amount of energy left over for the body to go about its functions and maintain homeostasis after the number of calories expended on exercise is subtracted from the number of calories consumed. Unsurprisingly, it is very important for overall health; low energy availability is a risk, whether it is linked to an eating disorder or not.

The results of the new study show definite patterns in dietary habits among female athletes with low energy availability and skipped periods, and enable the researchers to suggest specific nutritional changes that women can make to maintain their energy intake even when training at a high volume and intensity. Notably, replacing calories obtained through fiber with those derived from carbohydrates might significantly avert the risk of skipped periods and gynecological problems.

Writing in the Scandinavian Journal of Medicine & Science in Sports, Danish researcher Anna Katarina Melin and her colleagues describe studying the eating habits and health of 45 national-level and competitive runners, triathletes, and orienteerers who train at least five times a week. They trained an average of 12 hours per week, plus or minus six hours, and had an average VO2Max of 54.5 mL/kg/min.

The research focused on women whose eating habits are perceived to be normal or irregular, but not to a dangerous extent, and examine how this relates through exercise to health. In initial screening, 11 of the women were found to have disordered eating – that’s roughly 25 percent — and were excluded from the rest of the study.

Those with low energy availability trained 25 percent more than the other women, corresponding to 37 percent more energy being spent on training. Those who skipped periods had 15- to 20-percent lower fat mass on their bodies, although their body mass index (BMI) was not significantly different from athletes who did not skip periods. (This is yet another indication that BMI is not an accurate assessment of health or fat.)

Unsurprisingly, the researchers found that energy availability was associated with how many calories the women consumed, as well as with how many macronutrients, proteins, and fats were in their diet.

The athletes with low energy availability ate less energy-dense foods: that is, foods that provided fewer calories per gram. Athletes with low energy availability also ate fewer than the recommended amount of carbohydrates (6 g per kilogram of weight per day) and ate 26 percent less fat than athletes with optimal energy availability.

Usually, when female athletes have low available or energy or skip periods, it is recommended to gradually increase caloric intake by small amounts so as to regain health without gaining weight.

The research team suggests a more detailed approach: to consider how much energy is being expended in training, and then to make up the deficit in calories with the recommended amounts of protein and, in particular, carbohydrates, which so many of the athletes had been missing.

Meanwhile, the athletes who skipped periods showed a pattern of consuming more than the recommended amount of fiber per day, and much more than the women whose menstrual cycles remained regular.

The researchers write that while the general population is often encouraged to eat more fiber for very good reasons, exceeding the recommended amount of fiber intake brings consequences. A high-fiber diet leads to more excretion of fat and other energy sources, and some kinds of fiber also delay food processing so that an individual feels satiated and does not end up eating as much.

“These fiber-related effects are normally seen as beneficial,” the authors write. “However, in endurance athletes with a high total energy expenditure, they can potentially become problematic since high-intensity exercise also has been shown to have an acute suppressive effect on appetite.”

And finally, high levels of fiber intake have been shown in other studies to be related to lower estrogen levels. This is because estrogen, like fats, binds to fiber in the digestive tract and is excreted instead of being reabsorbed into the body. This might be the mechanism which leads the female athletes with excessively high-fiber diets to skip periods, which puts them at risk for other health problems.

Thus, in addition to making up missing calories with carbohydrates, the researchers suggested that women with low energy availability or skipped periods replace some of the fiber and whole grains in their diet with carbohydrates and energy-dense foods. In particular, they suggest drinking drinks that contain calories, such as juice, dairy, sports drinks, or smoothies, instead of water some of the time.

And, even though none of the athletes had diagnosed eating disorders, the team found that some had a “drive for thinness” related to their pursuit of excellence in their sport. These athletes, even though their diets were more or less following normal patterns, did tend to have lower energy availability and an increased prevalence of skipped periods.

Thus, the authors argue that even slightly restricting caloric intake can have health consequences.

“Our results indicate that even a slightly increased drive to lose or maintain a low body weight is associated with dietary characteristics likely to increase the risk for persistent LEA and FHA,” they concluded. “Handling the issue of leanness and body weight with care is therefore of paramount importance in sport environments.”

Chelsea Little

Chelsea Little is FasterSkier's Editor-At-Large. A former racer at Ford Sayre, Dartmouth College and the Craftsbury Green Racing Project, she is a PhD candidate in aquatic ecology in the @Altermatt_lab at Eawag, the Swiss Federal Institute of Aquatic Science and Technology in Zurich, Switzerland. You can follow her on twitter @ChelskiLittle.

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