It's mid-afternoon and your head is pounding. You realise your last drink was at breakfast. Lunch happened at the desk, in front of a screen, and whether you were full or just finished, you couldn't say. Your shoulders have been up near your ears since the morning meeting, and you only notice now, as they ache.
Your body was reporting all of this as it happened, and the receiver was turned down. That receiver has a name, a list of things that weaken it, and a surprising amount of room to improve.
The sense without a common name
The five senses that face outwards get taught in every school. The one that faces inwards rarely gets mentioned. Interoception is your sense of what's happening inside your own body: your heartbeat and breathing, hunger and fullness, thirst, a full bladder, warmth and cold, the tightening of muscles, and the physical side of emotions, the knot in the stomach or the heat in the face.
Science named it over a century ago. In 1906 Charles Sherrington, who later won a Nobel Prize for his work on nerves, described the receptors inside the organs as "interoceptive". The noun came later.
The messages travel up a long line. The vagus nerve runs from the base of the brain down past the heart and lungs to the colon, and 80 to 90 percent of its fibres carry news from the organs up to the brain rather than orders down. The body's main line to the gut mostly listens.
Much of the reading is done by the insula, a fold of the brain's outer layer tucked deep inside each side of the head. Its right front part is busy when you sense thirst, pain or tiredness and when you time your own heartbeat, and people with more grey matter there tend to read their insides more accurately.
Your brain reads these signals all the time, mostly below the surface, and uses them to keep you running. It's how you know to eat, drink, rest, cool down or slow down. When the signals come through clearly and you pay them some attention, you act on small needs before they become big ones. When they come through faintly, or you've learned to talk over them, you find out late, as a headache, an evening binge, a stiff neck or a crash.
Three different skills
Interoception covers three separate skills, and they often part company.
Accuracy comes first, meaning how well you detect what's going on inside. The standard way to measure it goes back to a test from 1981, and it's simple. Sit still for a minute and count each heartbeat you can feel, hands off your pulse, then check the count against the real number. Some counts land close. Others are wildly off.
Next comes how tuned in you believe you are, the answer you'd give on a questionnaire. The third is how well that belief matches your accuracy, whether your confidence in a count tells you anything about whether it was right. When 80 adults were put through all three, the three turned out to be distinct. Feeling sure of your body predicted only part of how accurate you were.
Meditators are the striking case. Experienced meditators from two traditions, Tibetan Buddhist and Kundalini, spend hours paying attention to their bodies, so they were expected to win the heartbeat count easily. They didn't. They did no better than non-meditators of the same age and weight, across several sessions. What they did do was rate their own performance higher and find the task easier. Feeling in touch and being accurate are different things, and accuracy can be trained directly.
Accuracy pays off well outside the lab. Traders on a London trading floor beat matched non-traders at the heartbeat count, and the more accurate traders made more money than their colleagues and lasted longer in the markets. The team behind the test put it down to the gut feelings that trading folklore has always talked about.
What turns the signal down
Long stress dims it. When you spend weeks on alert, pushing through and staying switched on, your attention tends to go to the outside world, and the inside one gets quieter. It works as a short-term survival trick and wears badly as a way of life.
Rules do the same thing more quietly. Eat at lunchtime because it's lunchtime, finish your plate because wasting food is wrong, have three coffees because that's how the day goes, keep going until the task is done. Each rule is sensible on its own. Stacked up over years, they teach you to take your cues from the clock and the to-do list instead of your body, and the body's own signals get harder to hear. It can start early, at a table where the plate has to be cleared before you may leave. In 1917, to stretch food through the First World War, Herbert Hoover's US Food Administration had schoolchildren pledge, "At table I'll not leave a scrap of food upon my plate." The Clean Plate Club came back in 1947.
Screens pull attention outward at the moments when inside signals matter most, at meals and at bedtime. Caffeine and sugar paper over tiredness so well that you stop noticing it until you're exhausted.
Age plays a part too. In 59 adults aged 22 to 63, the older they were, the worse they did at the heartbeat count, and age alone accounted for about 30 percent of the differences between them. It's one more reason to train the skill rather than assume it.
Hunger, fullness and the difference between them
Hunger is the signal that suffers most from the clock, and the cost shows up at the scales. Fullness takes time to build after you start eating, as hormones from the gut reach the brain. Eat fast and you can finish a large meal before the message arrives. When 30 women were served the same meal twice, eating it slowly once and quickly once, they ate about a tenth less at the slow meal and left feeling more satisfied. Why Some Foods Fill You Up and Others Leave You Hungry has what else decides how full a meal leaves you.
Real hunger and a craving feel different once you know the difference. Hunger builds gradually, sits in the stomach, and any reasonable food would do. A craving arrives suddenly, sits in the mouth or the mind, and wants one particular thing, usually something sweet, salty or crunchy. Stress, boredom and tiredness all produce cravings that pass for hunger until you stop and check.
What you eat changes how clearly the signals come through. Protein fills you up more than carbohydrate or fat does, and meals that start with meat, fish or eggs, with the fat that comes with them, keeps hunger quiet for hours. With the starch gone, blood sugar swings less, which means fewer false alarms, and when hunger does come back it builds slowly enough to read.
Tired, thirsty, sore or tense
Tired and sleepy are two different signals, and mixing them up costs sleep. Sleepiness is heavy eyelids and a nodding head. Tired means you feel drained and heavy while your mind stays wide awake. Going to bed tired but not sleepy is a reliable way to lie awake for an hour, so wait for the sleepy signal before you turn in.
Thirst is a fair guide on an ordinary day, and even during exercise, but it fades with age. When seven fit older men, all past 65, went 24 hours without water, they felt less thirsty than young men put through the same thing and drank less afterwards, even though their blood showed they were the more dried out of the two groups. Urine colour is a better check. In three tests, colour tracked how concentrated the urine was closely enough to use as a field guide: pale straw means you're doing fine, and dark yellow means drink.
Pain in training comes in two kinds. A dull, spread-out ache in the muscles you worked, at its worst one to three days later, is the normal soreness of a body adapting. Sharp pain in one spot, pain in a joint, or pain that gets worse the longer you keep going is a stop signal, and training through it is how small injuries become long ones.
Breath is often the first thing stress changes. Quick, shallow breathing high in the chest, with the shoulders doing the work, usually starts before you realise you're stressed. Catching it gives you an early warning, and a few slow breaths, each let out more slowly than it was taken in, turn the body's alarm down again. by James Nestor goes much further into how breathing shapes the rest of the body.
Emotions live in the body first
"Hangry" entered the Oxford English Dictionary in January 2018, defined as "bad tempered or irritable as a result of hunger". It also answered an old riddle, which asks for a third common English word ending in "-gry" after angry and hungry.
It's a whole word for hunger that shows up as a short temper before it shows up as hunger. Other feelings work the same way. Before you know you're anxious, your body usually does: a quicker heartbeat, shallow breathing, a tight stomach. Anger shows up as heat and tension, sadness as heaviness. The brain reads these changes and, partly from them, works out what you're feeling.
Reading those early signals helps you handle the feeling. In a test of 28 adults asked to calm their reactions to upsetting material by thinking about it differently, those with better awareness of their bodies brought their reactions down more. Missing the signals is how feelings seem to arrive from nowhere, fully formed.
For a minority, this link is weak. Alexithymia, a word coined in 1970 from the Greek for roughly "no words for feelings", means trouble recognising and naming your own emotions, and fewer than 1 in 10 have it to a high degree. Across two experiments, it went with poorer accuracy at the heartbeat count, while autism on its own didn't.
The problem can run the other way too. An anxious mind can read the body too loudly and too darkly: a racing heart becomes a heart attack, a flutter becomes a sign of something terrible. Accuracy helps here as well. In a test with 121 autistic adults, who often live with high anxiety, six sessions of heartbeat-counting practice with feedback on how close each count came left them less anxious three months later than a comparison training did. Accurate signals are less frightening than guessed ones.
Too much attention is its own problem
Tuning in has a limit. Watching every twinge, checking your pulse through the day and searching every new sensation online turns ordinary body noise into something that feels urgent. That kind of attention amplifies symptoms and feeds worry, and it leads to the opposite of what you want: a body you trust less.
The aim is accuracy. You want to notice hunger before you're starving, tiredness before you crash and tension before your neck locks, and then act and move on. The bulk of what the body reports is routine maintenance, and it only needs a routine response. How to Respond to a Symptom Without Ignoring It or Panicking, linked below, has the calm middle way for the signals that aren't routine.
Where a tracker fits
A ring such as the , or a watch, can help, used the right way round. Guess first, then look: decide how you slept before you open the app, and notice whether you feel run-down before you check your resting heart rate. Compared like that, the numbers train your own sense, the same way the heartbeat count does.
Letting the score tell you how you feel does the opposite. Sleep clinics now see patients chasing a perfect score until the chasing itself becomes the sleep problem, and they have a name for it, orthosomnia. Why You're Still Exhausted Despite Doing Everything Right has how far the trackers can be trusted. Treat yours as a second opinion.
How to sharpen it
Interoception improves with practice, and the practice is simple.
The heartbeat count. Once a day, sit still, close your eyes and count the heartbeats you can feel for one minute, hands in your lap. Then take your pulse at the wrist for a minute and compare. Do it for a few weeks and watch the gap. It sounds like a party trick, and it's the most direct training there is.
One meal without a screen. Choose one meal a day to eat sitting down with nothing else going on. Before you start, rate your hunger from one to ten, check again halfway through with the fork down, and at the end notice whether you're satisfied or stuffed. It takes a week or two before the signals start to stand out.
The pause before the fix. Before the coffee, the biscuit or the scroll, stop for a breath and ask what's going on: tired, thirsty, bored, hungry or tense? Often the answer is water, a walk or a minute away from the screen, and the coffee was only covering the tiredness.
A body scan at night. Lying in bed, move your attention slowly from your feet to your head, noticing warmth, weight and tension without trying to change anything. It sharpens awareness and calms the body at the same time, which makes it a good way into sleep.
Movement with attention. A walk, a stretch or a gym session done with some attention on how the body feels, where it's tight and where it's tired, trains the same skill. Headphones off for part of it helps.
Notes. A few words a day in a on energy, hunger, sleep and mood turn vague impressions into patterns. After a couple of weeks, the notes usually show something the day-to-day never did: the afternoon slump that follows a skipped breakfast, or the bad night after a late meal.
When a signal needs more than attention
Better body awareness also makes it easier to tell the everyday from the unusual. A signal deserves a closer look when it's new and different from your usual pattern, when it lasts for weeks, when it's getting steadily worse, or when it comes with warning signs such as weight loss without trying, fevers, night sweats, blood in your urine or stool, or pain that wakes you. Those are reasons to get checked, and spotting them early is among the most useful things good interoception does for you. 12 Signs Your Body Is Trying to Tell You Something Important, linked below, goes through what the common signals tend to point to.
Turn the receiver back up
Your body has been reporting on itself your whole life, a steady stream of small messages about fuel, water, rest and stress. Somewhere along the way you learned to override them with the clock, the to-do list and the next coffee. The receiver still works. It just needs using, and the next time a headache is on its way, you'll hear it coming before lunch.
Tonight, before bed, sit still for one minute and count your heartbeats. Then check them. That's the first rep.
Spotted a new symptom and can't decide whether it matters? How to Respond to a Symptom Without Ignoring It or Panicking — how to sort a fresh symptom into the urgent, the worth-booking and the wait-and-see.
Want to know what the common signals point to? 12 Signs Your Body Is Trying to Tell You Something Important — a dozen common symptoms, from tiredness that won't lift to night sweats, and the usual causes behind them.
Know someone who only notices they're hungry once they're starving? Send them this. A minute a day of counting heartbeats might change how they read the rest.
Tried something here, or got a question it didn't answer? Write to us at contact@allforlife.club. Your questions shape the next articles.
Disclaimer: This article is general information. For advice about your own health, talk to a qualified health professional. If you notice any of the warning signs described above, or a symptom is new, lasting or getting worse, get checked.
Affiliate Disclosure: This article contains affiliate links. As an Amazon Associate, All For Life earns from qualifying purchases, at no extra cost to you. We only link to products we would recommend without the commission.
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