Book Review

Inner Sense: how the new science of interoception can transform your health

by Caroline Williams (Profile Books, 2025)

Every so often, a new understanding about the body captures both scientific and public imagination, inspiring much research and seemingly explaining almost all oddities and ills. Recent examples have included the role of inflammation and prediction, and now the focus is on interoception – awareness of the sensations through which bodies communicate with brains. Interoception is endlessly fascinating, although I do wonder if managing it will have quite so dramatic an effect as science writer Caroline Williams suggests in the subtitle of her excellent book.

There is a lot to absorb. Williams masterfully weaves her way through the body, explaining and exploring the extent and impact of our interoceptive abilities. The brain, she makes clear, is nothing without the body. For instance, our heart beat not only reminds us that we are alive but somehow marks out our bodies as our own. Experiments show that our sense of self can more readily be extended to an inanimate object such as a rubber hand, if a projected version of it flashes in time with our own heartbeat. We are also quicker to notice and react to something new if it reaches our senses when our hearts are contracting, sending blood around the body. This makes sense in terms of the ‘fight-or-flight’ response, and can also lead to some misinterpretations.

The vagus nerve, as we know, is very popular right now, not least because of Stephen Porges’ polyvagal theory. In a section entitled “What really happens in vagus?”, Williams compellingly presents contradictory information from neuroscience which shows far greater complexity than the theory might lead us to expect.

In-depth exploration of messages sent from the gut to the brain reveals how this affects what and how we eat. Drugs like Ozempic, which tell the brain that the gut is full, may cause loss of appetite even for liquid, sometimes leading to dangerous dehydration. Meanwhile, a diet high in protein can make us nicer! We learn that neurons found in fat can detect pressure and stretching as well as light at wavelengths invisible to the naked eye, and that the light-sensitive receptors in fat are important for staying metabolically healthy – more intriguing evidence that “our bodies are sensing more about what’s going on inside us than anyone previously expected”.

Apparently people with hypermobile joints are 16 times more likely to have a panic attack than less supple others and Williams explains why: “Bendiness throughout the body disrupts bottom-up interoceptive signals”. Hypermobility is just one symptom of a genetic mutation that makes collagen throughout the body more stretchy; stretchier blood vessels don’t squeeze tightly enough to maintain correct pressure when someone stands up quickly or eats a large meals or gets too hot. The heart has to beat faster to compensate and the sensation may be interpreted as unease, leading to anxiety. Knowing this, and what to do, can help counteract it.

There is so much to learn. Brainstem processing doesn’t involve thinking but definitely affects state of mind. Feeling ‘tired all the time’ may be due to over-cautious body budgeting, arising from particular interpretations and predictions about what is going on inside us. Our bodies constantly emit tiny quantities of light and scientists have no idea why (but it might be telling that tumours emit vast amounts, their release due in some way to mitochondria, the ‘powerhouses’ of cells). Understandings about interoception are teaching us better ways to handle what is now termed ‘nociplastic pain’, where there is no clear evidence of damage to tissues or nerve pathways. And gentle touch, it appears, can be more soothing if applied before a painful procedure.

Ever keen to disabuse readers of any brain-body split, Williams emphasises that “the brain is neither the starting point for our mental experience nor the end point for our body’s live updates. The brain isn’t the control centre of the mind; it is more a collaborative hub where body and brain work together to decide what is the most sensible plan of action, given the current state of affairs.” The last chapter of this riveting book rounds up what we can all do to tune into our body rhythms and better manage our responses.

Reviewed by Denise Winn (Oct 25)