If you’re a female athlete, or even just a woman who likes to train hard, you’ve probably wondered if your nutrition is optimal. You’ve questioned whether the general recommendations for athletes are helping you get the most out of your body and your training.
This is an excellent question, especially since the vast majority of dietary suggestions for athletes are based on research performed on men. Top that unfortunate fact with the reality that a staggering 2/3 of collegiate female athletes are actively trying to lose weight and you might think that we have a bit of a problem.
In fact, studies show there’s a mismatch between nutrition recommendations and what women really need based on the limited studies done on female subjects. The whole situation is complicated by the social pressures that are placed on women to be thin and the often incorrect belief that a leaner athlete is always a better athlete.
Therefore, this article will discuss how women’s metabolism differs from men’s and provide evidence-based nutrition recommendations so that women can optimize both health and performance.
Gender Differences In Energy Needs
Female athletes tend to have a significantly lower energy intake relative to body mass than men. In fact, female athletes are commonly reported to be in an energy deficit because of a preoccupation with body image and pressure to achieve a low body fat percentage (1).
Although in certain situations, fat loss may be beneficial and warranted for overweight athletes, energy restriction will lead to the loss of lean mass, which will likely compromise performance. In addition, frequent dieters have been found to have higher body fat percentages, likely due to adaptive reductions in resting metabolic rate (2).
Some studies have found that female athletes, particularly those in endurance sports such as running, live in a chronic energy imbalance, consuming at or below their resting metabolic rate in calories daily. This is bad news because it consistently leads to hypothalamic amenorrhea (lack of period) in female athletes, and negative performance-related side effects such as fatigue, irritation, slower phosphocreatine recovery rates, increased stress fractures, and reduced thyroid hormone.
Similarly to patients with anorexia, exercising women have been found to have high levels of the appetite suppressing compound peptide YY. Interestingly they also have high levels of ghrelin, a hormone that typically raises appetite. However, it’s thought that in lean, female athletes with amenorrhea, the high peptide YY blunts the appetite raising effects of ghrelin.
Whatever the mechanism, one thing we know for sure is that adequate calories are necessary for optimal performance and recovery from exercise and the majority of female athletes simply aren’t getting enough. Scientists recommend that female athletes never go below 30 calories/kg of bodyweight a day, with ideal intakes being significantly higher. For strength/power or resistance-trained athletes, researchers recommend women consume 39 to 44 cal/kg bodyweight/day (1).
Because endurance-trained female athletes often have a higher exercise energy expenditure (they burn more calories during training), it’s recommended that they calculate calorie needs by multiplying kg of lean body mass by 45 (3). Then add estimated calories burned during exercise on top of that value.
Therefore, a 50 kg women with a body fat percentage of 15 percent would have a lean body mass of 42.5 kg and would require 1900 calories a day without exercise. Burning 500 to 600 calories during sport training would increase her daily calorie needs to 2,400 to 2,500 a day.
Gender Differences In Macronutrient Needs
If you’ve ever gotten nutritional advice from a sports dietitian, it’s likely they put a lot of emphasis on carbohydrates. However, research shows that women are less reliant on glycogen during exercise but utilize more fat for energy than men. This is thought to be due to the differences in sex hormones between the genders, specifically the greater concentration of estrogen and progesterone and lower testosterone in women (1).
Additionally, women appear to rely on burning intramuscular triglyceride stores for energy during exercise more than men. This has a muscle glycogen sparing effect. During sprints and resistance exercise, women have lower glycolytic enzyme activity and higher post-workout glycogen stores than men (5-7).
This has both performance and nutrition implications. By sparing glycogen and relying more on intramuscular fat stores, women may have a greater overall exercise capacity than men. In addition, they likely don’t need the same quantity of carbohydrate to restore muscle glycogen concentrations post-workout since not as much glycogen is depleted following the same relative work volume.
Furthermore, female athletes may benefit from a lower proportion of calories from carbohydrates and a higher intake from fat.
Of course, women still need high-quality carbohydrates from fruits, vegetable, beans and whole grains in their diets, but tunnel vision shouldn’t be on carbs while sacrificing protein and fat. This is especially important because surveys show that female athletes who are dieting often cut out fat in an effort to reduce calories.
Low fat diets may impair exercise performance, reducing intramuscular fat stores. They also compromise health: Adequate fat provides fat-soluble vitamins necessary for bone health and it helps support hormone production to prevent menstrual disturbances.
Therefore, it’s recommended that higher fat diets may be advantageous for female athletes in strength sports to complement energy production derived from intramuscular and circulating lipids (fats), while concurrently sparing muscle glycogen (1). Researchers recommend female endurance athletes in obtain at least 30 percent of their energy from dietary fat to ensure rapid replenishment of intramuscular triglyceride stores following exercise (3).
When choosing fat sources, quality is essential to improve fat metabolism and provide fat-soluble antioxidants, which protect against lipid peroxidation that commonly increases during intense resistance exercise. Choose fats from sources found naturally in lean protein foods, nuts, seeds, nut butters, fatty fish (for example, salmon and trout), fish oil supplements, avocados, and egg yolks. Avoid all processed and trans fats
In regards to protein, it’s commonly believed that female athletes don’t require as much as male athletes. Although studies are inconsistent with regards to gender differences in protein metabolism, women have a decreased rate of muscle protein synthesis after exercise (1). This suggests that women may need to consume MORE protein after resistance exercise in order to elicit the same anabolic environment and achieve a positive nitrogen balance.
Why is nitrogen balance important?
It is an indicator that your body is not breaking down lean muscle tissue for energy. Protein is also necessary for the body to maintain proper enzymes and hormones necessary for intense training programs.
Scientists recommend a protein intake in the range of 1.3 to 1.8 g/kg of protein for omnivorous female athletes to maintain nitrogen balance. Vegetarians may require on the upper end of this range, especially if they don’t eat eggs or dairy products frequently.
Vitamin & Mineral Needs Unique To Female Athletes
Iron needs are increased during exercise and women experience greater iron losses due to menstruation, which makes iron deficiency anemia one of the most prevalent deficiencies observed in female athletes. Risk is worse in vegetarian athletes because vegetarian iron sources have poor bioavailability (10 percent) compared to animal protein (18 percent), which provides the more absorbable “heme” iron (1,3).
Scientists recommend regularly testing for iron status and increasing heme iron-rich foods or supplementing with 18 mg/day when stores are inadequate. Of note, contraceptive use will lower menstrual blood losses by as much as 60 percent, decreasing iron needs from 18 to 11 mg/day.
Vitamin D deficiency rates are high for female athletes, ranging from 33 to 42 percent and may be even higher depending on the season and type of sport. Vitamin D is necessary for muscle function and immunity in addition to bone health. Female athletes are strongly recommended to test vitamin D levels quarterly and supplement with up to 5,000 IUs to maintain a blood value of above 30 ng/ml (1,3).
Calcium may need to be supplemented due to losses through sweat or with amenorrhea and low estrogen levels. Calcium can be found in green leafy vegetables (e.g., lettuce, celery), meat, fish, soy, rice milk, and certain legumes (peanuts). If supplementation is necessary, it’s recommended to take 1000 mg/day in two 500 mg doses from calcium carbonate or citrate (3).
Water and electrolyte needs are different between male and female athletes due to the influence of the menstrual cycle. For example, in the luteal phase (following ovulation until the start of a period) when estrogen and progesterone are elevated, a female’s core temperature increases by 0.6°C. During this phase sodium losses increase as well and the volume of water in the blood decreases. This combination puts women at greater risk of hyponatremia and dehydration.
Additionally, research shows that women have three times higher hyponatremia rates following marathons and ironman competitions, possibly because they overdrink water, which has a dehydrating effect by diluting sodium concentrations.
The solution is to increase electrolyte and protein intake surrounding training sessions, particularly during the luteal phase.
Creatine is a popular performance-enhancing supplement due to its ability to increase time-to-exhaustion and work capacity, however, studies show women almost never take advantage. Fear that creatine will increase body weight seems to be one reason that women shy away from creatine, but this is unfounded.
In fact, research indicates creatine is safe for women and will enhance anaerobic exercise performance without increases in body weight. Supplementation is particularly important for vegetarians who have deficient creatine stores, which may lead them to miss their high-intensity performance potential.
Four Key Take Away Points To Remember:
#1: Gender differences in fat burning and carb metabolism during exercise suggest macronutrient ratios and post-workout fueling recommendations need to be customized for female athletes.
#2: Adequate calories are absolutely essential for training recovery and health. Get between 39 and 44 calories/kg/bw a day. When doing high volume training, account for additional energy expenditure.
#3: Healthy fats from a variety of sources are necessary to support hormone balance and vitamin levels. Avoid a low-fat diet.
#4: Nutrient and hydration needs may vary based on the phase of a woman’s cycle or contractive use. Blood tests and a customized supplementation program can help avoid deficiencies.
Final Recommendations: Female athletes have unique nutrition needs for optimal performance and health. Use this information to customize a nutrition program that promotes athletic success and sets you up for a long and healthy life.