Energy availability in cycling is the energy left from what you eat once your training is paid for, per kg of fat-free mass. A 2026 UCI review by Louise Burke and colleagues treats 40 to 45 kcal per kg a day as adequate, with 30 often cited as a lower threshold, and warns that home estimates are rough.
What is energy availability in cycling?
The review is part four of our UCI nutrition series, one of the topic reviews behind the UCI's 2026 position on nutrition, published in the International Journal of Sport Nutrition and Exercise Metabolism. Burke, of the Australian Catholic University, and colleagues from Bath, Liverpool John Moores, Simon Fraser, Leeds Beckett and São Paulo universities, a Swiss cycling academy and a professional team define it with one sum. Take your energy intake for the day, subtract the energy your exercise cost, and divide by your fat-free mass in kg.
Energy balance asks whether you ate as much as you used over the whole day. Energy availability asks what was left for everything else once the riding had taken its share, and the authors point out that cycling's exercise cost can be very high, and that energy spent on the bike is gone for every other system. They describe low energy availability as a continuum. A brief dip that reverses, such as a hard block followed by proper recovery, is what they call adaptable. A longer or deeper shortfall, especially alongside other stresses, is problematic and is linked to the outcomes the IOC groups as relative energy deficiency in sport, or REDs.
How many calories does a bike ride burn?
Here a power meter helps more than most kit. The review notes that most power meter makers claim an error of about 1% to 3% for the work you do, and that riders turn about 19% to 23% of the energy they burn into work at the pedals, so the rest leaves as heat. One kilojoule of work at the pedals is about 0.24 kcal, which means each kilojoule your head unit shows cost your body roughly 1.04 to 1.26 kcal.
Take a 75 kg rider with 15% body fat, which gives about 64 kg of fat-free mass, riding 3 hours at an average of 170 W. That is 1,836 kJ of work, or roughly 1,900 to 2,300 kcal burned. To leave 45 kcal per kg of fat-free mass for everything else, about 2,880 kcal, that rider would eat roughly 4,800 to 5,200 kcal across the day. On a rest day the same target is about 2,880 kcal. Burke and colleagues stress that targets like these, worked out from simple equations, should be treated with extreme caution, as a rough guide and never as a fixed number to hit.
The review's own worked examples show how wide the spread is.
| Example rider in the review | Training | Estimated daily energy use | Intake for an energy availability of 30 to 45 |
|---|---|---|---|
| Woman, 22, mountain biker, 65 kg, 25% body fat | about 3 hours a day | 4,006 kcal | 3,024 to 3,756 kcal |
| Man, 32, road rider, 68 kg, 9% body fat | about 5 hours a day | 5,525 kcal | 4,407 to 5,336 kcal |
| Woman, 27, gravel rider, 72 kg, 16% body fat | 2 hours a day | 3,685 kcal | 2,750 to 3,658 kcal |
| Six professional men, 8 days of spring classics (Heikura, 2019) | race days against rest days | not reported | energy availability measured at 14 on race days against 57 on rest days |
Why do the big days leave riders short?
The professional data point at the long days. Ida Heikura and colleagues followed six professional men through 8 days of one-day races and found energy availability averaging 14 kcal per kg of fat-free mass on race days and 57 on rest days, with body mass and skinfolds unchanged across the block. The riders ate 10.7 g of carbohydrate per kg on race days against 6.4 on rest days, yet took only 51 g an hour while racing, short of the guidelines. In a second study cited by the review, 10 continental professionals training 21.5 hours a week ranged from minus 21.9 to 76 kcal per kg of fat-free mass over 7 days, and most had 1 to 3 lower days followed by a higher one. The review's authors read this as a shortfall from extra riding rather than from eating less, made up on the lighter days.
An amateur's version is the long Saturday ride after a working week. The review notes that even professionals' intake can stay much the same on bigger days, so eating enough on a 4 hour day takes planning, and a normal dinner can leave it well short.
Does where the shortfall comes from matter?
Burke and colleagues think it does. They cite evidence that a shortfall driven mainly by eating less may do more harm to muscle and bone than one driven by riding more, and when a rider is short they put eating more ahead of training less, partly because cyclists generally find that easier to accept than cutting their training. They also report how common restriction is. In a 2024 survey of 203 competitive cyclists, 145 men and 58 women, 5.7% had a clinical eating disorder and 16.7% had questionnaire scores indicating disordered eating, and in another survey 77% of 97 competitive male cyclists had tried to lose weight in the previous 12 months.
Their advice on body weight is to treat it as one metric rather than the goal. They suggest a flexible range in place of a fixed target, with the lower end kept for key competitions, and they note there is no evidence that deliberate changes in body mass or body fat are consistently associated with better or worse cycling performance.
How do you know if you are eating enough for cycling?
At home, you can't know it precisely. The review explains that food diaries usually under-report what riders eat, that the energy cost of exercise has its own errors, and that there are no clear thresholds separating adequate from low energy availability. For those reasons energy availability is not used to diagnose REDs. Clinicians use the IOC's REDs Clinical Assessment Tool, version 2, which works from signs and symptoms. If you are worried about how much you eat or how your body is responding to training, talk to a doctor or a registered dietitian.
Our view at WattPlan is that most amateurs should stop trying to calculate energy availability day by day and instead eat to the ride, because the kilojoule count from a power meter is the most reliable number in the whole sum and the days it is high are the days riders fall short.
WattPlan's workout player shows a running calorie count while you ride, worked out from your average power assuming about 25% efficiency, which gives about 0.96 kcal per kilojoule. That assumes you are more efficient than the 19% to 23% in the review, so the real cost of a ride is likely to be about 9% to 32% higher than the player shows. Its feed reminders ask for 60 g of carbohydrate every 45 minutes, about 80 g an hour, which covers part of a long ride's cost on the bike.
What to do this week
- Note the kilojoules on your two biggest rides of the week, multiply by 1.0 to 1.25 to get calories, and compare that with what you ate extra on those days.
- On long days, eat during the ride and plan a proper meal soon after, rather than waiting until you feel hungry.
- Keep protein up across the week. Our guide to how much protein cyclists need gives the amounts.
- Don't pair a big training block with cutting food. Talk to a registered dietitian before you try to change your weight.
- Keep any train-low rides to easy sessions you would do anyway, as in our train low guide, and never on a long or hard day.
What we don't know yet
The authors say most of the research consists of short controlled trials or observational snapshots that can't prove cause and effect. Most of the energy data come from professional road racing, and the authors call for more work on gravel and mountain bike stage racing and on how women and men respond differently. The 40 to 45 and 30 figures are reference points rather than proven cut-offs, and the review itself reports a scientific debate, between the IOC's REDs model and an alternative that puts several stresses on an equal footing, that is still going on.
Sources
- UCI Sports Nutrition Project: Body Composition, Energy Requirements, and Energy Availability in Cycling, International Journal of Sport Nutrition and Exercise Metabolism
- Alternate-Day Low Energy Availability During Spring Classics in Professional Cyclists, International Journal of Sports Physiology and Performance
- 2023 International Olympic Committee's (IOC) consensus statement on Relative Energy Deficiency in Sport (REDs), British Journal of Sports Medicine
- UCI Sports Nutrition Project: Position Statement on Nutrition for Cycling, International Journal of Sport Nutrition and Exercise Metabolism