Fueling research goes back to the 1920s, when Boston Marathon studies found that athletes who consumed carbohydrates performed better. The research has come a long way since then. We now know that combining glucose and fructose in a 1:0.8 ratio improves absorption. This knowledge increased fueling guidelines from 60 to 90 g/h, with many elite athletes aiming for 120+ g/h.
But an important question remains: do these guidelines apply equally to female athletes? The answer is more complicated than many people realize. We'll break it down here.
Quick answer: Female athletes should follow the same guidelines as male athletes (22.5 to 90 g/h depending on duration and intensity). However, because these guidelines are based on data from men, it is particularly important that female athletes monitor their response and adjust intake accordingly.
Want personalized guidelines? Use our Fueling Calculator.
A History of Underfueling in Female Athletes
For many years, female athletes were often encouraged — explicitly or implicitly — to eat less. Concerns about body weight, aesthetics, and outdated coaching beliefs led many women to chronically underfuel their training.
Chronic underfueling can lead to Relative Energy Deficiency in Sport (RED-S). While RED-S can also affect male athletes, it historically is more common in female athletes.
As nutritionist and research Tina Goršek Šparovec talks about here, symptoms like loss of menstruation or low energy availability were often normalized. As a result, many athletes did not receive treatment in time and suffered long-term consequences. RED-S also meant that many female athletes never met their full athletic potential.
Luckily, coaches and sports nutritionists are now much more aware of the problem, and they generally encourage female athletes to fuel adequately. However, the question remains of how much female athletes should fuel.
What Research Says About Carbohydrate Oxidation in Men vs. Women
One way researchers study fueling needs during exercise is by measuring exogenous carbohydrate oxidation, or the amount of carbohydrate consumed during exercise that is actually used for energy.
The findings are mixed:
- Two studies found no meaningful differences in peak carbohydrate oxidation rates between males and females. Differences were minimal (<0.1 g/min) and not statistically significant.1,2
- Three other studies observed slightly higher oxidation rates in males, typically 0.2–0.3 g/min more than females.3,4,5
None of these studies are definitive though. The study sizes were very small, most used recreationally-trained athletes, and all but one study used only glucose as the carbohydrate instead of a glucose-fructose blend.
The Bigger Problem: Women Are Missing From the Research
The problem isn’t just mixed results or small study sizes. It’s who the research studies.
A group of researchers conducted a large audit that looked at 938 carbohydrate fueling studies. It found that:
- 79% of the studies included no women at all.
- Of the 11,202 participants across all studies, only 11% were female.
In the studies which did include female athletes, only 31% defined menstrual status. None of the studies met researchers’ standards for controlling for ovarian hormone effects.
As a result, carbohydrate intake recommendations are largely derived from male data.
This matters because sex-based differences, such as metabolic rate, intramuscular fat content, and menstrual hormones, could influence carbohydrate needs. Whether they actually affect fueling requirements, and by how much, remains unclear.
What Female Athletes Should Take From This
Even though females are underrepresented in the research, the evidence we do have shows that female athletes can oxidize substantial amounts of ingested carbohydrates, and proper fueling clearly improves endurance performance.
Until we have more data to show otherwise, female athletes should follow the same fueling guidelines as male athletes. You can get personalized amounts in our fueling calculator.
However, because the guidelines are largely based on male data, female athletes need to apply guidelines more carefully.
Here are some practical tips for female athletes when applying these guidelines.
1. Don’t Follow Guidelines Blindly
Start with general fueling guidelines and then adjust them based on how your body responds. Note that this advice applies to all athletes, male and female, but it’s particularly important for females to monitor their response since the guidelines are validated in men.
2. Communicate with Your Coach and Nutritionist
Talk openly with your coach and nutritionist about how you feel before, during, and after training. This information helps them adjust your fueling strategy to meet your individual needs.
3. Speak Up
While it isn’t your responsibility to fix gaps in sports research, speaking up and sharing your experiences can help ensure female athletes are better represented and supported.