Our Athlete's Top Nutrition Questions Answered
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We asked our athletes to send us their most honest nutrition questions and put them to our Head of Nutrition, Laura Warren. No fluff, no upsells — just the science, applied. Here's what came back.
Long read. Skip to the section that applies to you.
Anthony — Ultramarathoner
Q. I've had a hunch that eating whole meals and foods with protein + fats always leads to better outcomes in performance efforts over 12 hours. But is there any actual evidence behind that? Should I be aiming for standard meals and a minimum amount of the other macro nutrients (not carbs) on 12+ hour efforts?
A: For endurance performance the evidence still leans heavily toward carbohydrates as the primary limiter, while protein/fat play more supporting roles (satiety, stability, muscle protection).
I'll try and break it down to assess the research and studies behind this but also acknowledge what works for one, doesn't necessarily work for all and being open to trialling in training a few different ways of fuelling leads to a clear understanding of what works the best for your unique body.
From a physiology standpoint here's what drives performance in 12+ hour physical efforts:
Carbohydrate (glycogen availability and intake) is still recognised as the rate-limiting fuel for endurance performance. This is because when intensity is anything above very easy aerobic, carbs dominate energy production. This recommendation is based on the basis that muscles predominantly use glycogen (stored carbohydrate) as fuel during moderate to high intensity exercise and performance typically drops when muscle and liver glycogen stores deplete. You may have experienced or seen people "bonk" in races. It's like a car running out of petrol.
There is plenty of evidence to back this up:
- Carb intake during endurance training/races is positively correlated with speed and finishing outcomes (1)
- Carb feeding during exercise improves capacity and ability to sustain intensity (2)
- Standard guidance still favours high-carb, moderate protein, low fat for endurance performance (3)
So in short, in ultra-duration events, carbs are still considered the performance throttle, not protein or fat.
But I also want to recognise your hunch regarding including protein + fat meals as these macros contribute to energy stability and durability.
Protein and fat have a number of effects on your body. They slow gastric emptying which supports more stable blood glucose. They reduce hunger which may lessen GI distress. Protein in particular contributes to less muscle breakdown over long durations and fats provide sustained energy at lower intensities.
What about fat-adaptation / low-carb approaches I hear you say…
There is a real mechanism here and I think it can certainly be amazing for some people once fat adaptation occurs — this takes time and commitment but once achieved can spare glycogen and help in very long, steady physical efforts.
The studies show fat-adapted athletes have a higher fat oxidation and similar endurance at moderate intensity but it doesn't consistently improve high-end performance (4). This approach could be advantageous to athletes who are unable to tolerate ingesting carbohydrate during a race though.
So what should you actually do for a 12+ hour ultramarathon effort given the current framework?
Carbs drive performance. Protein protects the system. Fat smooths the ride.
The ratios above are going to be unique to you and I encourage you to change things up if you feel you are plateauing in performance. Having a curious approach to nutrition and being open to trying new ways of doing things helps us quickly identify what definitely doesn't work and hopefully more of what does.
References
- Inamura, N., Taniguchi, H., Yoshida, S. et al. A comparative observational study of carbohydrate intake and continuous blood glucose levels in relation to performance in ultramarathon. Sci Rep 14, 1089 (2024). https://doi.org/10.1038/s41598-023-51048-6
- L.C. Dos Santos, C. de Moura Costa, R.C. de Moura, V.O. Silvino, M.A.P. Dos Santos, A.D.C.A.S. Brandão, Effects of carbohydrate supplementation on the performance of endurance athletes: a systematic review. Clin. Nutr. ESPEN 68, 198–205 (2025). https://doi.org/10.1016/j.clnesp.2025.04.021
- Helge JW. A high carbohydrate diet remains the evidence based choice for elite athletes to optimise performance. J Physiol. 2017 May 1;595(9):2775. doi: 10.1113/JP273830. Epub 2017 Feb 8. PMID: 28044326; PMCID: PMC5407959.
- Burke LM, Hawley JA. Effects of short-term fat adaptation on metabolism and performance of prolonged exercise. Med Sci Sports Exerc. 2002 Sep;34(9):1492-8. doi: 10.1097/00005768-200209000-00015. PMID: 12218744.
Maeve — Multisport athlete
Q. Sometimes I have extended fatigue after a race. What would you recommend I eat more of to get back to full energy faster?
A: The main causes of "extended fatigue" post-race lasting beyond 24–48 hrs are typically driven by:
- Low glycogen replenishment (carb intake is too low)
- Insufficient total protein or poor amino acid absorption
- Iron depletion (this is very common in female endurance athletes)
- Low B12 or overall energy intake in general
I'll aim to give a few easy to implement strategies but remember to trust your body with any changes you make — always listening to the whisperings it gives, as what works for one does not always work for all.
Acknowledging first that multi-sport training and races are very demanding on the body's resources, so as a foundation we have to adequately fuel.
The core strategy is to focus on the 4 R's of Recovery: Rehydrate, Replenish (carbs), Repair (protein) and Rest.
Rehydrate
Rehydration is a key priority after a multi-sport race, particularly if it has been very hot, you sweat a lot, or it is a long-distance event.
Aim to replace 150% of the fluid you lost within 4–6 hours of the race. You can work this out by weighing yourself pre and post-race. If you lose 500g (0.5kg) over your race, you will need 750mls (1.5 x 500) of fluid for recovery. 1 scoop Circl mixed into the 750ml of water is ideal here.
Replenish
Whole food carbohydrates are essential after a race because this restores your glycogen levels, which is the fastest way to get your energy back.
Target:
- 1.0–1.5 g carbs/kg bodyweight within 60 mins post-race
- Continue higher whole food carb intake for 24 hrs
Easy vegetarian options to try:
- Rice, sweet potatoes, pasta — can choose a GF option if applicable
- Oats + banana + honey + plant-based milk
- Dates with dark chocolate and nuts
- Fruit smoothies
- Muesli and fruit
- Wraps with hummus + roast veggies
Repair
Protein is essential for muscle repair. During multi-sport events, the body breaks down muscle protein for fuel; high-quality protein consumption shortly after exercise stops this breakdown and switches the body from a catabolic (breaking down) state to an anabolic (building up) state.
Target:
- 25–40g protein within 60 mins post-race
- 1.5–2.5 g/kg/day total
Vegetarian sources to consider:
- Eggs (if included)
- Greek yogurt
- Tofu or tempeh
- Lentils + rice combo
- Beans + quinoa combo
- Protein smoothies (pea or whey blends depending on what sits well)
It's often best to combine the carbs and protein into one smoothie or meal. Look at the above options to see what appeals to you — i.e. fruit, muesli and yoghurt or a tofu and roast veggie rice bowl.
Aiming for a carb:protein ratio of 3:1 or 4:1 works well for most people.
Rest
It's crucial that Rest is recognised as vital after a multi-sport race, to allow the body and mind to recover from the intense, cumulative stress of the physical and mental challenge it is. During rest the body repairs the microscopic muscle tears, replenishes energy stores, and reduces inflammation, leading to improved performance rather than burnout.
It's important we touch on Iron, as this can be a major fatigue driver in female endurance athletes in general.
Low iron = low oxygen delivery = lingering fatigue.
The best way to rule this out is a blood test through your Doctor or a walk-in at Awanui Labs. I'd like to make note here that the laboratory "normal" range for ferritin for adult women is 20–380 µg/L. Normal ranges are not always optimal — I've seen over and over in my clinical experience that the majority of women feel better when ferritin sits between 50–150 µg/L. Below 50 µg/L, the body often shows signs of fatigue, poor sleep, low mood, restless legs. Below 30 µg/L, those whispers tend to become shouts. If persistent fatigue is a concern you can supplement (if your blood levels are below 50 µg/L) — look for an easy to absorb form like Iron Bisglycinate. Pair with vitamin C (broccoli, citrus, tomatoes) and avoid tea/coffee the hour either side of taking, to enhance absorption.
You could also increase your intake of foods that contain non-haem iron.
Examples include: lentils, chickpeas, spinach, kale, pumpkin seeds, dried fruit (apricots, figs), blackstrap molasses, and quinoa.
Vitamin B12 is another nutrient I would recommend getting a blood test to assess, as it is crucial for red blood cell production, nerve function, cell repair, and converting nutrients into energy. Low B12 has often been described by clients as fatigue that feels like "flat battery" that just can't recharge.
Vegetarian food sources to include are dairy / eggs (if included), fortified plant milks — or supplementation is often necessary, particularly for those on a vegan diet.
Total calories should be monitored as this can often be the hidden issue — it delays recovery even if your macros look "clean."
What this could look like in practice:
Immediately post-race (within 60 mins): Smoothie — banana, berries, oats, protein powder of choice, coconut water or plant-based milk (ideally one that is not full of vegetable oils). This ensures you hit carbs + protein fast.
2–3 hrs later (proper meal): Big buddha bowl is a good option — choose a rice, pasta or quinoa base, add tofu/tempeh or eggs, roasted veg, plus an olive oil based dressing.
Ongoing (next 24 hrs when not sleeping): Aim to have a snack/meal every 3–4 hrs. Some options:
- Yogurt + fruit + muesli
- Nut butter and honey on toast
- Trail mix with dried fruit
- Hummus, veggie and tofu wraps
If fatigue persists despite incorporating the recovery strategy:
- Check ferritin and B12 levels
- Review overall hydration and energy intake
- Look at sleep quality, pre-race and during race hydration and fuelling strategies
Jordan — Head of Brand, Circl Health
Q. What is the no.1 thing most aspiring athletes miss in their nutrition protocols?
A: In my experience the most consistently missed piece isn't some exotic supplement or macro ratio — it's fuel timing and total energy availability.
Most aspiring athletes underperform not because they eat "badly," but because they don't eat enough, at the right times, to support their training load and recovery. That leads to chronic low energy availability (1).
When you think of many aspiring athletes, they are fitting their training in around full-time jobs, maybe family or other business commitments.
They tend to train hard — often multiple sessions in a day. They may eat "clean" but restrict calories unintentionally and delay or skip key fuelling windows because of lack of awareness on how this affects performance.
Doing this long term results in glycogen that is never fully replenished, hormones and recovery are compromised, which ultimately leads to performance that plateaus or even declines.
You may recognise yourself in one of these patterns:
- Under-fuelled or under-hydrated pre-session
- Not eating or drinking enough during long training efforts
- Missing the 0–2 hour recovery window — most common mistake. This is when the body is primed to absorb carbs + protein.
How to fix:
1. Preparation is key
- Treat nutrition as part of the session itself. Fuelling should be planned and practiced, not reactive.
2. Fuel the work (during)
- 30–90g carbs per hour (depending on intensity/duration)
- Fluids + electrolytes layered in
3. Optimise the first 2 hours post-training
- Carbs: ~1–1.2 g per kg bodyweight
- Protein: ~20–40g
- Recovery should start immediately, not "when convenient." Take 5–10 mins post-session to slow down the breath — inhale 4, out for 7. Focus on the diaphragm drawing in the breath and then relaxing. This cues the parasympathetic nervous system, which is the "rest, digest, heal and repair" state we need to be in to absorb nutrients fully and recover. Ideally your drink/food is prepped and brought with you to your training session/event so it's ready to be consumed within 60 mins.
4. Eat enough across the day
- If you're hungry all the time, feeling flat, or craving sugar later in the day — use it as the sign it is: you're under-fuelling and need to make changes.
- Remember, energy intake needs to match output, not appetite.
References
- Beck KL, Thomson JS, Swift RJ, von Hurst PR. Role of nutrition in performance enhancement and postexercise recovery. Open Access J Sports Med. 2015 Aug 11;6:259–67. doi: 10.2147/OAJSM.S33605. PMID: 26316828; PMCID: PMC4540168.
Chris — Founder, Circl Health
Q. From a nutrition and supplementation perspective, what are the top 3 things to boost recovery?
A: If you strip recovery down to what actually moves the needle physiologically, three things matter most: glycogen repletion, muscle protein synthesis, and fluid/electrolyte balance.
Here is what I consider the "top 3" recovery strategies…
1) Carbohydrate timing + adequacy (glycogen restoration)
After training, your muscle cells are primed to take up glucose (via GLUT4 translocation and increased insulin sensitivity). If you don't capitalise on that window, recovery — and your next-session performance — will lag.
Within 0–2 hours you want to ingest ~1.0–1.2 g carbs/kg bodyweight. Some good options are fruit, rice, sweet potatoes, oats.
For multi-session days: repeat carb feeding every 2–4 hours.
2) Sufficient protein dose (muscle repair + adaptation)
Within ~2 hours post-exercise ingest 20–40g high-quality protein (eggs, chicken, fish, tofu, tempeh, whey, pea or bone broth protein powders are good options) and then spread high-quality protein across the day (every 3–4 hours).
This helps maximise muscle protein synthesis signalling (via the mTOR pathway) and accelerates repair.
3) Fluid + electrolytes (rehydration + cellular function)
Many athletes rehydrate poorly — either under-drinking or replacing water without adequate electrolytes.
Aim to replace ~125–150% of fluid lost (weigh yourself before/after sessions if you want precision). It's important to include sodium (500–1000 mg/L) in fluids, especially after heavy sweat loss. You can add potassium/magnesium if you are cramping or it's a long-duration effort. Thankfully we have Circl, which takes the guesswork out of the electrolytes for us.
By restoring plasma volume we improve nutrient delivery, which supports nerve/muscle function and reduces fatigue carryover.
Where supplements actually fit (secondary, not primary):
Once the above are nailed, a few supplements deserve notable mentions:
- Creatine monohydrate: 5g daily — improves strength recovery, repeated sprint ability, and cellular hydration
- Omega-3 fatty acids: ~1–3g EPA/DHA — may reduce inflammation and soreness (DOMS)
- Magnesium: 200–400mg — supports muscle relaxation and sleep quality
References
- Beck KL, Thomson JS, Swift RJ, von Hurst PR. Role of nutrition in performance enhancement and postexercise recovery. Open Access J Sports Med. 2015 Aug 11;6:259–67. doi: 10.2147/OAJSM.S33605. PMID: 26316828; PMCID: PMC4540168.