Nutrition for The Female Athlete - Part 1
Any individual athlete’s nutritional needs depend on sex and body size, as well as the intensity and duration of exercise. A healthy nutritional intake is essential for both male and female athletes to ensure they have sufficient energy to fuel their exercise and to promote adequate recovery. However, most nutritional recommendations are based on research performed in male subjects, and there are some key aspects with regard to female athletes that make them more susceptible to certain nutritional imbalances.
THE FEMALE ATHLETE’S ENERGY NEEDS AND INTAKE
Female athletes typically display a lower energy intake relative to body weight than their male counterparts. They tend to restrict their energy intake, especially in sports where they are pressured to have a low body fat percentage, such as endurance running or where appearance is rated, such as gymnastics. This is dangerous since it puts the female athlete at a higher risk of developing certain nutritional imbalances and may compromise their performance. If the restriction is imposed consistently, some female athletes may develop medical and/or psychological issues such as disordered eating, loss of bone mineral density, and amenorrhea (loss of menstrual cycle). The ‘female athlete triad’ refers to a combination of these three components and the female athlete may not necessarily present all three. It is actually more common to present one or two of those components, with 50-60% prevalence among certain athletic groups. It is a tricky condition since it encompasses a spectrum with different degrees of severity, making it hard to both diagnose and treat.
Although it is not that easy to quantify the precise energy requirement of an athlete, the general consensus is that a female athlete’s minimum energy requirement is 39-44 kcal/kg fat free mass/day for strength-trained athletes and 45 kcal/kg fat free mass/day for endurance-trained athletes since they often have higher energy demands. In practice, for a 60 kg athlete having a body fat percentage of 17% and lean mass of 49.8kg, the energy required should be at least 1942-2191 kcal/day and 2241 kcal/day, respectively.
This represents the energy required for healthy living without taking into account the energy necessary to fuel exercise. For example, if a training session has resulted in an energy expenditure of 500 kcal, the daily total energy intake would increase to 2442-2691 kcal and 2741 kcal, respectively.
Physiologically, the mechanism for chronic restriction of energy intake still remains unclear, although there is some research highlighting the importance of appetite-regulating hormones. Similar to anorexic patients, female athletes with amenorrhea typically display high levels of peptide YY (an appetite-suppressing hormone). In contrast, they also present high levels of ghrelin (an appetite-stimulating hormone). However, to compensate the increase in energy intake, it is thought that the high levels of peptide YY blunt the effects of ghrelin.
THE FEMALE ATHLETE’S MACRONUTRIENT NEEDS AND INTAKE
Female athletes tend to be less reliant on glycogen (stored carbohydrate) during exercise and use more of their fat stores to fuel their exercise than men. This is thought to be due to differences in sex hormones. The effect of carbohydrate loading also does not seem to be as beneficial in females compared to men, although it has been shown that females may benefit from an intake of >8g of carbohydrate/kg bodyweight/day before race day. Nevertheless, this should be tested at an individual level since some athletes may prefer and do better on a higher fat intake to fuel their performance.
An adequate fat intake is also essential for health to provide fat-soluble vitamins and ensure sex hormone production to support menstrual function. The recommendations are that female endurance athletes obtain at least 30% of their energy through good-quality fat sources such as oily fish, nuts and avocados to ensure the restoration of their intramuscular triglyceride stores, a major fuel source during endurance exercise. For strength-trained athletes, higher fat diets may be advantageous since these athletes rely less on glycogen stores to fuel their exercise and seem to be less responsive to glycogen resynthesis after the intake of carbohydrates during recovery.
It is thought that female athletes do not need as much protein as their male counterparts, yet a study measuring nitrogen turnover in endurance-trained female athletes estimated their protein requirement to maintain nitrogen balance (indicator of the body’s protein balance) to be 1.63g/kg/day, which is within the range recommended for male athletes doing the same volume of training5. Therefore, current recommendations for protein intake are within 1.2-1.8 g/kg/day for female athletes. Strength-trained athletes should aim to consume towards the higher end to stimulate muscle protein synthesis for optimal recovery and the growth of fat-free mass.
In the next issue of SSC, I will be focusing on two areas that are often overlooked: the female athlete’s micronutrient needs and intake, and hydration. One thing is certain if a female athlete is not meeting her energy needs, she is most likely not going to be meeting her micronutrient needs… so the first aim should be to ensure that caloric intake is adequate for her training demands. Most of the time, this is sufficient to see an improvement on the playing field but, more importantly, in her health and well-being.
Deldicque, L. & Francaux, M. (2015). Recommendations for healthy nutrition in female endurance runners: an update. Front. Nutr. 2:17.
De Souza, MJ., Nattiv A., Joy, E., et al. (2014). Female athlete triad coalition consensus statement on treatment and return to play of the female athlete triad: 1st International Conference held in San Francisco, California, May 2012 and 2nd International Conference held in Indianapolis, Indiana, May 2013. Br J Sports Med, 48:289.
Manore MM. Exercise and the Institute of Medicine recommendations for nutrition. Curr Sports Med Rep. 2005 Aug. 4(4):193-8.
Volek JS, Forsythe CE, Kraemer WJ. Nutritional aspects of women strength athletes. Br J Sports Med. 2006 Sep. 40(9):742-8.
Houltham, S.D. & Rowlands, D.S. A snapshot of nitrogen balance in endurance-trained women (2014). Appl Physiol Nutr Metab, 39:219-25.