As a sports dietitian, I have noticed so many female athletes struggling to fuel adequately for their training. A runner setting out for a three-hour run on an empty stomach. A gym session fuelled by coffee. A low-carb protein bar.
Most of our guidelines for sports nutrition come from studies on endurance trained males. Coupled with societal pressures with messages of 'less is best', no wonder female athletes are confused.
This critical gap in knowledge has motivated me to research female athletes and what they need to fuel their training, with a particular focus on team sports.
As I approach the end of my PhD studies, here are the five things that have surprised me the most:
Rebekka Frazer conducts testing with athletes using wearable devices for her research.
Wearables can be very misleading
Fitbits, Apple Watches, WHOOP bands and Garmin are increasingly being used by athletes to quantify training load, but just how reliable are they?
Wearable devices are useful for things like tracking distance and heartrate trends. But they also give an estimate of the energy you've expended during exercise and research shows they're producing some huge inaccuracies in that guess.
An accurate measure of exercise energy expenditure usually requires laboratory equipment to assess oxygen consumption and carbon dioxide production. This typically requires wearing a metabolic mask while exercising - which is not practical in most real-world settings.
The problem is that many of these devices rely on algorithms that assume all exercise is steady state and relatively low intensity, and for this type of training, wearables are pretty handy. However, once that intensity picks up, the wearables fall over.
Low to moderate intensity cycling or running is very different to the intermittent, high-intensity exercise characteristic of team sport with bursts of activity and rest.
In my last study we took a group of female athletes through both a game simulation (to replicate field-based training for team sport) and a resistance training session. For the game simulation, we found that exercise energy expenditure was underestimated by up to 172 calories or overestimated by up to 65 for a 30-minute session. A one-hour resistance training session could be underestimated up to 200 calories.
Individual variation was huge too, and what was "slightly inaccurate" for one participant was way off for another.
So, when people say, "I burnt 500 calories, so I can eat 500 calories more today,' it's not that simple.
We know for some, tracking activity has a favourable impact on promoting more movement across their day and that's a good thing. Just don't use a wearable to dictate your food intake.
Women are often dramatically under-fuelling for exercise
One of the biggest issues I see is that people tend to eat the same thing day in, day out. They don't adjust for training loads at all.
This might be fine for someone doing half an hour in the gym a couple of times a week, but it's a very different story for the woman training for an ultramarathon with three-hour Saturday runs.
When someone fails to accommodate the additional calorie needs of their sport, it can result in low energy availability, where there isn't enough energy left to keep the body healthy and functioning properly.
When this inadequate fuelling is sustained for long enough, it can have adverse impact on both performance and health, including menstrual function, bone health, etc.
In one of our studies, we measured energy availability in a group of female soccer players during pre-season.
Not one athlete achieved optimal energy availability and all failed to upregulate their intake of food on training days to meet current sports nutrition guidelines for carbohydrates.
Lea Bachmann of Switzerland disappointed and dejected after her out during the Pole Vault Women at day three of the World Athletics Championships Tokyo 2025 at National Stadium on September 15, 2025 in Tokyo, Japan. Photo by Daniela Porcelli/Getty Images.
There's also a subset of athletes that believe if they can achieve a certain physique with lower body fat, that they're going to be faster and perform better. The research doesn't support that, but it is, I dare say, quite an ingrained belief.
Which brings me to my next point on how to fuel….
Everyone is pushing protein, but women desperately need carbohydrates
There's an overemphasis on protein, and that's because protein sells.
You can take a regular cheese, one that's always had a naturally high protein content, and simply rebrand it "protein cheese" without changing the nutrient panel at all, and it sells instantly. The same with high-protein bread, high-protein meals. The marketing is relentless.
Protein is important, but what's getting lost is that carbohydrates are your body's preferred fuel source for high-intensity exercise.
When women become fearful of carbohydrates and replace them with protein, they're neglecting what their body actually needs to perform.
We tested this in a trial of 15 female rugby players during a 7 week preseason. We provide all athletes with food on training days but only half the group were provided with a greater amount of carbohydrates (the amount recommended by current sports nutrition guidelines). All athletes provided with this greater amount of carbohydrate on training days gained more muscle over the 7 weeks without an increase in body fat. Contrast that with the group who did not get extra carbohydrate, and only 50% of those athletes gained muscle.
Your protein needs are the same for rest days as they are for training days, but your carbohydrate needs increase as your training load increases.
Rebekka Frazer's research is advancing understanding of energy availability and within day energy balance in female athletes.
Generally speaking, a piece of fruit before a training session is fine if you're exercising less than an hour. But if you're going out for these long runs, then we need to be fuelling a bit more substantially.
Flavoured oat sachets with a bit of honey on top is quite a popular option. Or a couple of pieces of raisin toast would be appropriate. An Accredited Sports Dietitian is the best person to provide more individualised advice based on your goals, preferences and current training load.
Protein is really well-placed after exercise and spread throughout the day. That helps with recovery but also helps you maintain your muscle mass. So maybe finish a run with some eggs on a bagel with juice, or high-protein yoghurt with granola and fruit to meet your recovery needs, and continue with more protein hits throughout the day.
When athletes are adequately fuelled, they feel better and are potentially better able to adapt to the training. Train to get faster, stronger and more resilient, not to burn calories.
Women's iron levels drop quickly, and we need to monitor this better
Iron is a big one. Men only need around 8 mg of iron per day. Women of menstruating age need 18 mg due to menstrual losses
This is additional to iron lost through sweating and footstrike haemolysis where tiny blood vessels burst on impact while running.
Iron deficiency makes everything feel harder. Training feels harder, life feels harder. And because women tend to normalise feeling "a bit tired," it gets overlooked again and again.
In one club I worked with, the men had access to supplements, regular medical testing, and ongoing monitoring. The women received none. It was up to each female player to stay on top of their own iron status.
For one of my studies, we collected blood samples at the start and end of a seven-week pre-season period and saw that iron levels had declined across the board. Two out of 15 female athletes were iron deficient at the start and levels in all 15 athletes had dropped by almost 20 percent on average by the end.
Faith Nathan in action during an Australia training session ahead of the Perth SVNS at Charles Riley Memorial Reserve Field 1 and 2 on 5 February 2026 in Perth, Australia. Photo by Paul Kane/Getty Images for Rugby Australia.
This is why we need to be monitoring women's iron levels better, and I'd suggest a check every at least every 12 months (or more frequently if you've experienced iron deficiency in the past).
Iron is one of the easiest things to fix, and it can make a huge difference to how a woman feels both on and off the field.
Women tend to normalise "feeling a bit off"
This might be the thing that underpins all the others.
In my research and practice, I keep seeing that women just accept feeling tired, flat, or worn down as "normal". I did it myself when I discovered I was stage two iron deficient.
I told my GP, "I am a bit tired, but I also have a lot going on."
It was the same with many female athletes in my studies who were juggling work, uni, family and training. They assumed their tiredness was normal.
But as I learned from my own iron deficiency, feeling tired often means something has been under-supported for a long time.
I've worked with both men and women's teams. Female athletes are typically under-resourced, yet are expected to perform at the same level as their male counterparts.
Female-specific sports science research is lacking because our physiology can require more complex study designs.
As a result, many current recommendations are based on male-focused research, which is not always translatable to women.
That's why I'm doing this work. And it's why I want this information in the hands of as many women as possible - because feeling "a bit off" shouldn't be the norm.
Female athletes deserve the support and advice that works for their bodies.
Rebekka Frazer is an accredited sports dietitian and PhD candidate in UniSC's School of Health .
