How low fuel can show up in runners

Runs feeling harder, or slow to recover

The IOC's 2023 statement lists slower endurance performance, a weaker response to training, and not recovering between sessions among the effects of running low on energy. A hard block, stress, heat, poor sleep, or being sick can do this too.

Sleep

Sleep trouble is on the IOC statement's list of emerging signs, which means researchers are still studying the link. Stress, pain, and a new schedule are common causes too.

Getting sick more often

The IOC statement lists getting sick more often among the health effects of low energy in athletes. Heavy training blocks and busy seasons at work or home can play a part too.

Stomach trouble

The IOC statement lists stomach and gut trouble, during exercise and on regular days, as an emerging sign that researchers are still learning about. It has many other causes, from certain foods to race-day nerves.

Mood and drive

If your mood has been low for a while, it's worth talking to a doctor or someone you trust. The IOC statement lists more stress, worry, and mood changes among its emerging signs, and lower drive to train among the effects on performance. Life stress causes all of these too.

Periods stopping or spacing out

First: if there's any chance of pregnancy, a pregnancy test is the place to start.

The IOC statement lists missed periods, and periods that come far apart, among the signs sports doctors look at. Many other things can cause this, like thyroid changes, PCOS, or perimenopause, and a doctor can check for them. It's worth bringing up at your next visit.

On hormonal birth control

Hormonal birth control can change or stop bleeds, so period changes can't be read the usual way while you're using it. The IOC statement makes the same point.

Pregnant or recently had a baby

We left the questions out of your results. Tiredness, sleep changes, stomach trouble, and mood changes are all common during pregnancy and after a baby, so this list doesn't fit this time well. Your OB or midwife is the best person for questions about eating and running right now.

After menopause

Periods don't apply as a sign after menopause, so we left that question out. Most of the research behind this list was done in younger athletes, so the other cards may fit less neatly. A sports medicine doctor can help sort that out.

Bone stress injury

The IOC statement lists bone stress injuries in the past two years among the signs sports doctors look at. Bone health depends partly on getting enough energy. Mileage, shoes, and running form matter too, so a sports medicine doctor can look at the whole picture.

Running without eating first

Plenty of runners head out without eating, especially early in the morning. If you'd like to try something first, small and simple works: a banana, toast with honey, or a glass of juice.

Nothing on long runs

Many runs don't need any food. Long ones are different, and that's when something in your pocket starts to matter.

Busy days

Busy days are when meals slip.