Why Do You Feel So Bad After an Ultra Endurance Event

Why You feel So Bad After an Ultra

You expect to feel tired after you’ve finished an ultra event. What you don’t expect is to feel off for weeks and sometimes even months later.

Low energy, poor sleep, gut issues, no motivation to train - all of it can lead to a nagging thought:

‘Have I actually done some damage?’

Is All that Sugar Harmful?

You might be wondering whether those days/weeks living off coke, slushies, sweets, fastfood and pies has taken a more longer-term toll on your system, affecting your recovery after an ultra.

During long events your body is expending massive amounts of energy (Mark Beaumont reckoned it was around 9000 calories per day on his round the world record).

Eating high calorie, easily digestible food isn’t just practical, it’s necessary. And because that energy is being used almost immediately its effect on your metabolism is very different from everyday eating.

What Research Suggests

Here are a few facts you might find reassuring:

Insulin and sugar

Eating excess sugar is the main cause of diabetes. When you are using all the sugar you eat this changes the way your body processes it and the insulin response is different. During an ultra, the sugar you’re consuming is being used immediately, not stored.

Fat/Weight Gain

In ultra-endurance events, the challenge is usually meeting energy demands, not overeating. Most athletes finish in a calorie deficit not surplus. For this reason fat can be a sensible choice as it is very high in calories (e.g. Killian Jornet is reported to have consumed large amounts of olive oil on his attempt to link 14,000 foot peaks across the United States).

Gut Stress and GI Issues

Gastrointestinal problems are a commonly cited problem for failing to complete ultra endurance events especially for runners. They can also unfortunately at times linger beyond the duration of the race.

IBS like symptoms

These can include sudden urgent bowel movements, loose stools abdominal pain and flatulence.

Not only are these unpleasant, they can also affect your ultra endurance recovery as your body struggles to absorb nutrients and maintain hydration.

Running in particular can cause more significant gastrointestinal damage often referred to as leaky gut where waste from the gut finds its way into the blood stream due to an increased permeability of the gut lining.

Whilst it’s always sensible to get yourself checked out by a medical practitioner in most cases the body is able to recover normal gut function given enough time. A common approach is a temporary low FODMAP or simplified diet followed by a gradual reintroduction of food groups. In many cases, this is enough to allow the gut to settle and recover.

The Real Causes of Fatigue After an Ultra Endurance Event

In fact the most common problem we see is people simply coming back to training too soon after ultra events causing a more latent and longer lasting fatigue.

The kind of people who sit on a bike for day after day for many hours or run long into the night and into the next day love to move…they tend to struggle with rest on a psychological level.

If you are still carrying post-event fatigue from something you did some months previously the chances are you simply came back before your body was ready. Recovery is part of training, not a break from it.

In addition to this there are some more supported real risks associated with long-term health and ultra endurance events:

1) Low Energy Availability

You can read more about RED-S and Low Energy availability here. In short if you do not fuel your body enough it will adapt in ways that compromise your health and performance by slowing down your metabolism and reducing non-essential hormone production. This leaves you at risk of deficiencies in key vitamins and minerals and makes you illness and injury prone…and yes you will feel very very tired.

2) Poor fuelling timing

Often people can be following a very healthy diet but they are not fuelling their training adequately. A good example is trying to complete a hard morning workout before eating or drinking anything. Your body needs sugar to go fast and your muscles need to be hydrated to work properly.

In general the best strategy is to have a high carbohydrate snack or light meal 1-2 hours before a hard workout (that is an intense workout above zone 2 or any workout lasting more than 90 minutes, in which case you should also be fuelling during the workout).

3) Poor Recovery Nutrition Post-Event

Many people still work on a ‘calories in - calories out’ protocol but the reality is we don’t really know how much fuel we need day to day. Certainly after a long ultra event your body will continue to need high levels of protein, fat and carbohydrate to recover, even though you are not exercising. Failure to fuel well in the hours and days after the event can compromise your recovery and leave you unable to come back strong and healthy.

4) Ultra-Processed Diet Creeping into Daily Life

Ultra processed food is addictive…and it’s not good for us long term; our gut needs fibre and fermented/pickled food and our body needs vitamins and minerals to support a healthy immune system. Developing a taste for processed food and simple sugars during a long ultra event can leave you more vulnerable to making those food choices outside of training and events leading to poor gut health and excess calories in day to day life.

5) Oral hygiene

There is good evidence that eating and drinking large amounts of high sugar, acidic food and drinks can compromise your dental health, causing cavities and gum disease, which can then affect your overall health.

Good ways to avoid this are:

• Two bottle system - for every mouthful of your favourite sports drink drink a mouthful of plain water

• Clean your teeth, regularly (not always a priority 36 hours into a 56 hour ultra event)

• Rinsing your mouth with water regularly

What Actually Helps Recovery After an Ultra

So here are some things you can do to promote your recovery after your ultra:

• Give yourself enough rest and recovery post-event (you can read more about how to do this here).

• Fuel well and stay hydrated during your event

• Eat and stay hydrated in the hours and days after

• Prioritise a balanced diet (protein, carbohydrates, fruits and vegetables)

• Re-establish normal balanced diet within 24-48 hours of completing, but be aware your body may need more fuel than usual for several days as it continues to recover

• Look after your teeth at all times, even during your ultra events

• Watch out for signs of low Energy Availability (see list of symptoms in this article)

Further Questions

How long does fatigue last after an ultra endurance event?

Fatigue can last several days to weeks depending on recovery, nutrition, and training history. The key is to listen to your body and come back according to what your body is capable of. Remember, it often takes longer than we expect or hope for and recovery is not linear - you can feel good one day and very tired again the next.

Is it normal to feel unwell after an ultra?

Yes — symptoms like fatigue, poor sleep, and gut issues are common, but prolonged symptoms may indicate under-recovery or illness. Always get yourself checked out if you feel seriously unwell and go to the emergency room if needed.

Should I rest completely after an ultra?

Some rest is essential; it's usually best not to plan any formal workouts for at least two weeks, although a gradual return to some gentle movement is usually beneficial once recovery has started.

If you’re struggling to feel like yourself again after an ultra, it’s rarely just about what you ate during the event.

We help endurance athletes break cycles of fatigue and return to consistent, sustainable performance.

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