The female trainee, and the female athlete have a lot on common, and are subject to similar stressors, it is important we take a second to look at these in any discussion of health, to identify and attempt to minimize them. After all, a healthy athlete is a productive one. Benardot states such things as the ‘female athlete triad’ (that is: eating disorder, menstrual dysfunction, and low bone density) p. 218, should be taken seriously.
Benardot states some of the ways women may have different nutrient intakes to men: some are due to body composition differences (males generally have a higher metabolic mass), some are due to body size (males having a larger body size than females generally), and some are due to physiological differences such iron intake with women needed twice as much (due to the blood loss during normal menses). That said, as Benardot states: “Energy intakes, for all athletes, are based on total weight, weight of the metabolic mass, and duration and intensity of exercise.” (Benardot, 2012, p. 219) Thus, dietary programs need to consider some different variables when being created for men and women. (p.219)
The first prong of the female athlete triad: eating disorder, is manifested and reported Benardot states in surveys of female athletes (p. 219) by a underconsumption of energy “leading many to assume female athletes are at an elevated risk of developing eating disorders regardless of what type of sport they are participating in.” (Benardot, 2012, p. 219) The question of what a female athlete should ingest in terms of energy should be informed by their goals, food availability, habits, and of course substrate utilization, and Benardot states there are some relevant differences between men and women, as in regards to fat utilization.
Studies indicate that females have a higher lipid, lower glycogen (carbohydrate), and lower protein utilization than do males athletes during endurance exercise. Because glycogen storage is limited, the lower rate of glycogen utilization gives females what appears to be a clear advantage over men in long-duration, lower intensity athletic events. This also gives rise to the following questions: Should female endurance athletes have a different energy substrate consumption pattern than male endurance athletes given the difference in the pattern on substrate utilization? No solid evidence indicates there should be a difference in intake, and the nature of endurance and endurance events still makes carbohydrate storage (glycogen) the limiting substrate in performance.(Benardot, 2012, p. 219)
From a performance aspect for female athletes, fat should not prioritized as a macronutrient for exercise, nor should it be heavily reduced either. Benardot states many female athletes who desire to lower their bodyfat percentage levels excessively drop their fat intake (the study he cites shows, that fat intake is 6 percent lower in amenorrheic athletes versus eumenorrheic athletes, that is lower in athletes with no menstrual cycle for 3-6 months versus those with a normal menstrual cycle) p. 220 Given, Benardot states, the high energy needs of female athletes, and the fact that women have an excellent system for catabolizing fat for energy fat should range in the 20 to 25 percent of total energy intake.
Weight loss is important to most athletes, and women need to be aware of the risks of severely depleting caloric intake to lose fat, the author states that such a strategy could be particularly unwise, even if we ignore the associated health risks (and exposure to eating disorder, or disordered eating that can arise with such a strategy), simply because it doesn’t work. Benardot states that although lowing calories can be desirable to lose bodyfat, that there is a reasonable and manageable way to do so. Going to extreme lengths to strip bodyfat can actually have the reverse effect, that is it can negatively effect lean mass rather than fat mass. Moreover, getting to extremely low levels of bodyfat itself (Benardot states that a range of 17-22% is needed to maintain normal menstrual function in most women, p. 233) can itself be harmful in that reproductive function can be compromised, which in turn lead to bone density issues.
Severely calorie restricted diets can negatively affect vitamin intake as well as negatively and consequently affect bodily functions. Benardot states that female athletes on restricted diets (that is diets below the recommended dietary intakes for their particular sport), can present with zinc, vitamin B6 issues, and studies have found that iron and calcium can be low in endurance athletes.
Adequate calcium consumption is necessary to develop and maintain high-density bones that are resistant to fracture, and iron is necessary for oxygen delivery to working cells… Ensuring adequate calcium intake is within easy reach of every athlete, but it should be understood that calcium intake by itself does not ensure good bones. Calcium, vitamin D, estrogen, and physical stress are all needed for bone development. Surveys have found low storage iron (ferritin) in female runners, and other studies have found that female athletes with anemia can improve aerobic performance through iron supplementation. (Benardot, 2012, p. 221)
Benardot is quick to state of course that iron should be regularly assessed by professionals before supplementation is taken up.
The female athlete triad does not have any particular horn set in isolation, one influences or is influenced by the other, as such restricted caloric diet can negatively affect the other prongs leading to irregular menses which can lead to bone density issues, both of which will be discussed at length in another post. Expect some overlap.
Benardot. D. (2012). Advanced Sports Nutrition. Champaign, IL. Human Kinetics.
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