Cyclists don’t get a free pass when it comes what they eat, just because they ride a bike regularly.
If you’re hoping to lose a few pounds or kilos, you can still clock up the miles and find you’re not losing weight – and if you aren’t, you can look to your diet.
The simple fact is that if the calories in exceed the energy out, the energy deficit required for weight loss isn’t being met.
There is certainly no shortage of diet options for us to better manage our eating, but as committed cyclists, it needs to be tailored for the work our bodies are doing.
This huge array of restricted-calorie diets at our disposal can also have the effect of freezing us into inaction. One way of eating, however, focuses more on when you eat rather than what: intermittent fasting. You can’t even call it a diet – it’s an eating pattern.
Its ideas and mainstream appeal draw on the ancient eating patterns of our ancestors, who would hunt for their food and go far longer without it than the ready supply many in the Western world enjoy in the 21st century.
Intermittent fasting's proponents argue that the way of eating that delivered us to 2026 as the dominant species on the planet is better than the diets of plenty that have left nations such as the USA and UK facing an unprecedented obesity crisis – and all the knock-on consequences to our health.
It also, research suggests, has many benefits to our health above and beyond weight loss, such as a longer, healthier life, a sharper mind and even how our bodies respond to diseases such as cancer.
Processing calories requires a lot of work for your body’s cells and the simple act of giving them a rest has been shown to help it recycle damaged cells and repair itself.
Food-free time
Intermittent fasting can be practised in various ways, but broadly speaking, it’s a pattern of eating that involves longer periods of time without calories than you’re likely used to – sufficiently long to kickstart your body’s fat-burning processes for fuel.
Your liver’s glucose stores deplete after around 12 hours, so in burning your (often plentiful) fat stores, ketones are released and used as an alternative fuel source by your muscles and nerves. This is called metabolic switching.
Arguably the most popular and easy-to-maintain type of intermittent fasting, the 16:8 pattern, takes your body beyond 12 hours up to 16 hours of fasting, with the remaining 8 hours the time when you consume your daily calories.
An alternate method, the 5:2 pattern, involves ‘normal’ eating five days a week, with reduced calories (typically around 600) on the two other days (ideally not back-to-back).
Neither method – and particularly time-restricted methods such as 16:8, which don’t specify daily calorie intake – gives a green light to eating as you please. If you keep up your calorie intake pre-fasting, you’re clearly not going to lose weight.
As Red Bull-Bora-hansgrohe team sports nutritionist Will Girling says, it is “physiologically impossible to lose more fat in one day or another, if they are completely identical, the only difference being is that in one you just haven’t had breakfast. The caloric expenditure is the same on both days.”
By simply the act of shrinking the time in the day when you do eat, it reduces the chances that you will eat as much as previously, through better appetite control and less snacking.
Fuelling for sport
The very valid question that you, as a cyclist, will have however, is whether intermittent fasting is appropriate or compatible with endurance sport.
Girling finds intermittent fasting an “incredibly interesting area of nutrition” but warns that people who are very active or have goals around sports performance should be wary. Women should also think twice, given different hormonal responses to fasting than men.
A pro athlete or an amateur engaged with big goals in endurance should typically avoid it, certainly as a permanent, consistent change.
“You might be waking up at 6am to smash out an hour’s exercise and crack on with your day, then come back home and have dinner with your family. There are some real implications for your social life and your performance life,” says Girling.
“If we have hard work to do on the bike, or some high-intensity work in the gym, at all points we’re looking to maximise fuelling, maximise carbs to facilitate performance and then have sufficient protein and possibly carbs to support muscle recovery and replenishment. Intermittent fasting may well not fit into that.”
Fasted training
The idea of fasted training is intermittent fasting in miniature – not a regular routine but cherry-picked up to several times a week to fit in with your exercise goals.
In a fasted session, you’d do your morning ride at a low intensity, having not taken on board calories since dinner the evening before, in order to train your body to burn fat for fuel.
Per gram, fat contains more than twice the energy of carbohydrate and can be stored to a far greater degree – although this energy doesn’t come as fast.
Until a few years ago, it was a hugely popular protocol in professional cycling. Races were often a war of attrition, so training your body to use fat for fuel and preserve precious carb stores for later in a race was what many riders were doing.
It certainly didn’t suit all riders, however, and training so much and lacking energy was a real problem for those flirting with burnout.
The foot-to-the-floor racing of the past five or six years – let’s call it the era of Tadej Pogačar – has changed all that and riders need fast, abundant energy from kilometre zero because racing is so frenetic and gung-ho.
That’s led to a carbohydrate boom in pro cycling as riders train their gut to handle as much as 180g of carbohydrate an hour without their bowels (metaphorically) exploding. Not so long ago, 60g an hour was what riders raced on.
Fasted training’s decline can also be attributed to long-term studies not showing a benefit for elite cyclists, says Girling. It’s still included in riders’ training sessions, albeit far more seldom, “perhaps once or twice a week in the easier part of the season”.
“Am I well, did I have a good night’s sleep, do I have a tickle in my throat? All these caveats apply [to fasted rides] because fasting increases the cortisol response, suppresses the immune system further and exposes us to more potential sickness,” he adds.
A personalised approach
Many of the trends of pro cycling eventually trickle down to us at home, but where does fasted training, or a longer intermittent fasting pattern, fit into our cycling life?
“We really need to be looking at what our goals are,” says Girling. He points to an amateur cyclist he’s working with who trains alongside his job as a pilot.
“He rides competitively and flies four days a week, and on those four days we do intermittent fasting because it’s easier for his day.
"He’s busy, he’s awake a lot of hours of the day and he gets more clarity without having meals that sometimes aren’t ideal for the circumstances he’s in. But for the days he’s at home and not working, he’s doing hard four-hour rides and he’s fuelling those days.
“It’s the same with me – if I’m travelling with the team and I’m going to be in airports or planes all day, and the food is rubbish, then I might intermittent fast that day.
"It always comes back to the goals – what are we trying to achieve? Is it performance and recovery or are we trying to manage our day and not overeat calories and see a steady increase in our body composition?”
Female cyclists, particularly those engaged with high-intensity exercise, should also be more wary of training while fasted, and post-menopausal women should avoid it altogether.
The cortisol spike during a fasted ride can hinder recovery and limit fat loss, while the decline of oestrogen during menopause makes women more prone to osteoporosis (weakening of bones). Training while fasted can hasten the breakdown of bone.
- Read more: Stop fasting, plan around your cycle and work on strength – how women can boost their fitness
Recreational riders
What about the people riding their bikes for health reasons, who ride at a slower, steadier pace for less time and don’t need to concern themselves with getting race-ready?
Neuroscientist Mark Mattson is the preeminent expert on intermittent fasting of this century and research from his lab at the National Institute of Aging in Baltimore, Maryland (which he retired from in 2019) over 20+ years led directly to the popularisation of the eating trend.
After retirement, he worked on his book The Intermittent Fasting Revolution: The Science of Optimising Health and Enhancing Performance. Published in 2022, it brought together all his and others work on the subject to date and showed what people can gain from incorporating it into their lives.
He’s been intermittent fasting for 30 years, mainly on the 16:8 pattern, and is a fan of exercising in the fasted state, saying it has several health benefits.
“Because intermittent fasting or exercise can on its own improve learning and memory, the combination of the two can help optimise cognitive performance,” he says.
The same is true, he says, for ‘autophagy’ (where old, damaged cells are broken down and recycled) and mitochondrial biogenesis (the creation of new mitochondria, an important part of adaptation to exercise that helps energy metabolism efficiency improve).
