What is periodised nutrition?

Periodised nutrition means planning what you eat around the purpose of your training: the session, the week and the phase of the season. It applies to everyday meals as much as to race-day fuelling. It must also protect your health and fit around the rest of your life.

Take a typical week for a cyclist. Tuesday might be 6 × 4 minutes at VO2max power, Wednesday a 90-minute recovery spin and Saturday a five-hour endurance ride. For a runner, swap in a track session, an easy 40-minute jog and a long run. Each of those days asks something different of the body, so the fuel it needs differs too. 

At Science to Sport (S2S) we sum this up as:

Fuel for the work required, recover for the work ahead.

The first half comes from a carbohydrate periodisation framework published by Impey and colleagues (2018). The second half is our reminder that what you eat today also sets you up for the demands of tomorrow.

Why nutrition should change with training

How much fuel you need depends on how long and how hard you train. As intensity rises, working muscles rely more on carbohydrate, stored as glycogen in the muscle and liver. During endurance events lasting up to about three hours, carbohydrate availability becomes a limiting factor for performance (Hawley & Leckey, 2015).

Carbohydrate also shapes how you adapt. Completing selected sessions with lower carbohydrate availability increases cell signalling linked to endurance adaptations, such as building more mitochondria (Bartlett et al., 2015). Whether that leads to better race results is less clear, and we come back to it under principle 3.

Energy and protein matter every day, whatever the session. Fall short on either and you recover and adapt less well, and over time your health suffers too.

We can think about periodised nutrition according to six principles.

1. Fuel for the work required

The amount of carbohydrate should be matched to how long and how hard the training session is. A high-intensity session needs enough carbohydrate to hit and hold the target power or pace. A long session needs more carbohydrate in total, while an easy recovery session needs far less.

The joint position statement from the American College of Sports Medicine, the Academy of Nutrition and Dietetics and Dietitians of Canada gives these daily targets for periods of optimised training or racing (Thomas et al., 2016):

The same statement sets targets around the session itself. For sessions longer than 60 minutes, it recommends 1-4 g/kg of carbohydrate in the 1-4 hours beforehand. During the session itself, targets scale with duration:

Some professional cyclists now take in more than 90 g per hour, but the performance benefits of these high carbohydrate intakes are still being validated and should only be attempted after deliberately training the gut to cope (see principle 5).

After exercise, if the next hard training session is less than 8 hours away or you are competing in multi-stage or multi-race events, aim for 1-1.2 g/kg per hour for the first 4 hours. With a full day between sessions, your total intake over the day matters more than exact timing.

For an easy ride or run of an hour or less, water and your usual meals will cover you

2. Fuel the athlete first

Before fine-tuning carbohydrate around sessions, make sure you are eating enough overall. With high training volumes, intake can easily fall behind what you burn without you noticing.

Two terms often get mixed up. Energy availability is the energy left for the rest of the body once the cost of training is subtracted, expressed per kg of fat-free mass (Thomas et al., 2016). Carbohydrate availability is how well your carbohydrate stores and intake cover the fuel demands of a specific session.

You can lower carbohydrate availability around one easy session and still meet your energy needs across the day. Problems start when low energy availability is severe or lasts for weeks. That drives Relative Energy Deficiency in Sport (REDs), which negatively affects hormones, bone, immunity, mental health and performance. The latest International Olympic Committee’s (IOC) consensus statement also flags low carbohydrate availability as an added risk, potentially magnifying the impacts on health outcomes (Mountjoy et al., 2023).

Warning signs for REDs include ongoing fatigue, frequent illness, performance that stalls despite good training, bone stress injuries, low libido, and missed or irregular periods. If these sound familiar, see a sports doctor or sports dietitian.

At S2S the order matters: fuel the athlete, then fuel the work. More advanced strategies, such as training with low carbohydrate, come after that.

3. Carbohydrate adjusts with training, protein and fat remain constant

We recommend that protein and fat stay fairly steady from day to day, with carbohydrate changes to meet the energy demands of training. Protein supports muscle repair and adaptation, which continue daily, rest days included. Fat supplies essential fatty acids and helps you absorb fat-soluble vitamins, and those needs don’t change much with training either (Thomas et al., 2016).

For protein, the Union Cycliste Internationale (UCI) Sports Nutrition Project consensus statement on nutritional periodisation recommends at least 1.6-2.1 g/kg per day for endurance athletes, or 112-147 g for a 70 kg athlete (Morton et al., 2025). It suggests 30-45 g per meal, including after key sessions.

We set fat at 0.8-1.2 g/kg per day, or 56-84 g for a 70 kg athlete. The daily target may be slightly lower on days when carbohydrate is high to reduce the risk of gut distress and slightly higher on rest or lower training days to help meet overall energy needs.

With protein and fat catered for, carbohydrate meets the rest of the day’s energy needs, so it rises on big training days and falls on easy ones.

Where "train low" fits

Some athletes deliberately start selected easy sessions with low carbohydrate availability. One version is “sleep low”: a hard session in the evening, little or no carbohydrate overnight, then an easy session before breakfast. In trained triathletes, three weeks of this was shown to improve 10 km run time by about 3%, even though daily carbohydrate intake was the same as in the control group (Marquet et al., 2016). 

The wider evidence base is less convincing. A 2021 meta-analysis of nine studies in well-trained endurance athletes found no overall performance benefit of restricting carbohydrate around targeted sessions compared with training with normal carbohydrate availability (Gejl & Nybo, 2021). Cutting carbohydrate across the whole diet is a different matter again: high-fat, low-carbohydrate diets don’t improve performance and limit your ability to work at high intensity (Hawley & Leckey, 2015).

Train low is an advanced tool, and at S2S we apply it through the glycogen threshold hypothesis proposed by Impey and colleagues (2018). It suggests that signalling for endurance adaptation is especially enhanced when muscle glycogen stays within a window of roughly 100-300 mmol/kg dry weight during a session. In practice, that means starting at or just below 300 and finishing no lower than 100. Starting much lower is likely to compromise training intensity (Hearris et al., 2019), and finishing much lower may blunt the signals for muscle protein synthesis.

Glycogen can't easily be measured outside a lab, so we estimate it from each athlete's recent training and food intake. We then adjust carbohydrate meal by meal so that selected low-intensity sessions fall within that window while key sessions stay fully fuelled, and only in athletes who already meet their energy needs.

4. Periodise nutrition around the training programme

Fuelling individual sessions is only one part of periodised nutrition. The same thinking applies across the week, through a training block and over the season, with the training programme setting the demands (Stellingwerff et al., 2019). The UCI Sports Nutrition Project consensus statement describes periodisation as adjusting energy and nutrient intake across these time scales to support adaptation, recovery, body composition and competition performance (Morton et al., 2025).

The nutritional focus changes with the phase of training. In a high-volume block, the priority is fuelling the work and recovering well enough to repeat it day after day. In a taper, volume drops and carbohydrate comes down with it, before carbohydrate loading at 10-12 g/kg per day in the 36-48 hours before races longer than about 90 minutes (Thomas et al., 2016).

In the off-season, or when injury cuts training, energy needs fall. Matching intake to lower demands can help avoid unwanted gains in body fat, while protein stays high to protect muscle (Thomas et al., 2016).

Nutrition can also be periodised around individual body composition goals. If an athlete is aiming to lose body fat, the American College of Sports Medicine joint position statement recommends doing it in the base phase or well away from competition (Thomas et al., 2016). Compared to a high energy deficit, a modest deficit of about 250-500 kcal a day, with weight loss kept below about 1% of body mass per week, can help to preserve muscle and performance.

Protein needs are higher when in an energy deficit, likely above 2 g/kg per day (Morton et al., 2025). The deficit also needs monitoring, so it doesn’t become prolonged or result in severe low energy availability (Mountjoy et al., 2023).

5. Practise race fuelling in training

Race-day fuelling should be rehearsed in training, partly because the gut adapts to regular carbohydrate intake during exercise (Jeukendrup, 2017b). In endurance-trained cyclists and triathletes, 28 days of training with carbohydrate increased how much carbohydrate they burned as fuel during a 100-minute ride, by about 16% (Cox et al., 2010). In endurance runners, two weeks of daily gut training cut gastrointestinal symptoms by about 60% and improved a 1-hour running test by 4-5% (Costa et al., 2017).

Long rides, long runs and race-pace sessions can be used to test your pre-race meal and its timing, and how many grams of carbohydrate per hour you tolerate at race intensity. Try out which drinks, gels, bars or chews sit well, how you will carry them, and how much fluid you need in the conditions you expect.

Intake should build gradually over several weeks rather than jumping straight to a race target.

6. Individualise the guidelines

Every number in this article is a guideline. The position statements describe their targets as general recommendations, to be fine-tuned around each athlete’s energy needs, training and feedback from training performance (Thomas et al., 2016 and Morton et al., 2025). No single method or diet meets every athlete’s needs in every situation (Jeukendrup, 2017a).

Turning those guidelines into a plan that works for you is where a performance nutritionist adds value. At S2S, we use the evidence-based ranges as the starting point and refine them from the feedback you give us, so your nutrition keeps supporting your goals.

Useful feedback includes how key sessions went, how well you recovered, your energy and hunger through the day, gut comfort when fuelling, sleep, and changes in body mass, health or your menstrual cycle. Small, regular adjustments based on that feedback build a plan that fits how you train and live.

How we work at S2S

The coach sets the training, and the nutritionist plans fuelling around it. We start with the sessions where fuelling makes the biggest difference, usually the hardest and longest ones. Over time, the aim is for athletes to understand the reasoning well enough to make these calls themselves.

Practical takeaways

• Plan your nutrition around your training week. Mark the hard and long sessions first, and put most of your carbohydrate before, during and after them.
• On easy and rest days you need less carbohydrate, so eat accordingly, but keep your total energy intake adequate and consider how you are training tomorrow.
• Keep protein steady: 1.6-2.1 g/kg per day, in meals of 30-45 g, including after training.
• On the bike or on the run, aim for 30-60 g of carbohydrate per hour for sessions of 1-2.5 hours, and up to 90 g per hour for longer ones.
• Take the warning signs of low energy availability seriously: ongoing fatigue, frequent illness, stalled performance, bone stress injuries, low libido or missed periods.
• Treat train low as optional. Keep it to easy sessions and skip it if your energy intake isn’t consistently adequate.
• Rehearse race fuelling in training, at race intensity, with the food and products you will use on the day. 

References

Bartlett, J. D., Hawley, J. A., & Morton, J. P. (2015). Carbohydrate availability and exercise training adaptation: Too much of a good thing? European Journal of Sport Science, 15(1), 3-12. https://doi.org/10.1080/17461391.2014.920926

Costa, R. J. S., Miall, A., Khoo, A., Rauch, C., Snipe, R., Camões-Costa, V., & Gibson, P. (2017). Gut-training: The impact of two weeks repetitive gut-challenge during exercise on gastrointestinal status, glucose availability, fuel kinetics, and running performance. Applied Physiology, Nutrition, and Metabolism, 42(5), 547-557. https://pubmed.ncbi.nlm.nih.gov/28177715/

Cox, G. R., Clark, S. A., Cox, A. J., Halson, S. L., Hargreaves, M., Hawley, J. A., Jeacocke, N., Snow, R. J., Yeo, W. K., & Burke, L. M. (2010). Daily training with high carbohydrate availability increases exogenous carbohydrate oxidation during endurance cycling. Journal of Applied Physiology, 109(1), 126-134. https://doi.org/10.1152/japplphysiol.00950.2009

Gejl, K. D., & Nybo, L. (2021). Performance effects of periodized carbohydrate restriction in endurance trained athletes: A systematic review and meta-analysis. Journal of the International Society of Sports Nutrition, 18, Article 37. https://doi.org/10.1186/s12970-021-00435-3

Hearris, M. A., Hammond, K. M., Seaborne, R. A., Stocks, B., Shepherd, S. O., Philp, A., Sharples, A. P., Morton, J. P., & Louis, J. B. (2019). Graded reductions in preexercise muscle glycogen impair exercise capacity but do not augment skeletal muscle cell signaling: Implications for CHO periodization. Journal of Applied Physiology, 126(6), 1587-1597. https://doi.org/10.1152/japplphysiol.00913.2018

Hawley, J. A., & Leckey, J. J. (2015). Carbohydrate dependence during prolonged, intense endurance exercise. Sports Medicine, 45(Suppl 1), 5-12. https://doi.org/10.1007/s40279-015-0400-1

Impey, S. G., Hearris, M. A., Hammond, K. M., Bartlett, J. D., Louis, J., Close, G. L., & Morton, J. P. (2018). Fuel for the work required: A theoretical framework for carbohydrate periodization and the glycogen threshold hypothesis. Sports Medicine, 48(5), 1031-1048. https://doi.org/10.1007/s40279-018-0867-7

Jeukendrup, A. E. (2017a). Periodized nutrition for athletes. Sports Medicine, 47(Suppl 1), 51-63. https://doi.org/10.1007/s40279-017-0694-2

Jeukendrup, A. E. (2017b). Training the gut for athletes. Sports Medicine, 47(Suppl 1), 101-110. https://doi.org/10.1007/s40279-017-0690-6

Marquet, L. A., Brisswalter, J., Louis, J., Tiollier, E., Burke, L. M., Hawley, J. A., & Hausswirth, C. (2016). Enhanced endurance performance by periodization of carbohydrate intake: “Sleep low” strategy. Medicine & Science in Sports & Exercise, 48(4), 663-672. https://doi.org/10.1249/MSS.0000000000000823

Morton, J. P., Hearris, M., Fell, M. J., Owens, D. J., Halson, S., & Trommelen, J. (2025). UCI Sports Nutrition Project: Nutritional periodization: Strategies to enhance training adaptation and recovery. International Journal of Sport Nutrition and Exercise Metabolism, 36(3), 279-304. https://doi.org/10.1123/ijsnem.2025-0073

Mountjoy, M., Ackerman, K. E., Bailey, D. M., et al. (2023). 2023 International Olympic Committee’s (IOC) consensus statement on Relative Energy Deficiency in Sport (REDs). British Journal of Sports Medicine, 57(17), 1073-1097. https://doi.org/10.1136/bjsports-2023-106994

Stellingwerff, T., Morton, J. P., & Burke, L. M. (2019). A framework for periodized nutrition for athletics. International Journal of Sport Nutrition and Exercise Metabolism, 29(2), 141-151. https://doi.org/10.1123/ijsnem.2018-0305

Thomas, D. T., Erdman, K. A., & Burke, L. M. (2016). American College of Sports Medicine joint position statement: Nutrition and athletic performance. Medicine & Science in Sports & Exercise, 48(3), 543-568. https://doi.org/10.1249/MSS.0000000000000852