Bad Appetite

The social, psychological, and biological drivers of appetite.

The Biology of Body Image

How your insular cortex could make you feel fat.

Have you ever felt like some part of your body was…not really yours? I’m not talking about phantom limbs or alien babies here – more about a subtle sort of discomfort with a significant body part. An obstinate muffin-top that insists on poking over your waistband perhaps. Breasts that have always been a little larger than you wanted them to be. Or thighs and buttocks that stubbornly fail to look like Gisele Bundchen’s no matter how many different pairs of skinny jeans you attempt to squish them into.

Well a group of scientists from Australia and England think you should probably blame your insular cortex. Wedged between the frontal and temporal lobe, deep inside the cerebral cortex, the insula is one of the most well-connected, multi-tasking structures in the brain. Pain? Taste? Empathy? Disgust? Attention? Perception? Awareness? The insula’s got it covered. In fact a recent meta-analysis found that the insula was activated in about a third of all neuroimaging studies.

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One function that might be particularly relevant to one’s butt-related grumbles, though, is something you might call ‘body representation’ – working together with brain areas involved in basic perception, like the somatosensory cortex, the insula helps to create an integrative model of one’s body.

If you have a malfunctioning insula that isn’t properly listening to signals from other brain regions, the researchers argue, this could give you a genuinely distorted body image. Conceptions of body parts that undergo rapid expansion, e.g. the hips, legs and trunk during the pubertal growth spurt (or maybe some other period of rapid weight gain, like the first year of college…) could be the most vulnerable to insula efficiency.

Now I admit I'm stretching the theory a little bit here – the ‘insula hypothesis’ was developed as an explanation of the various symptoms of anorexia, rather than of common-or-garden body dissatisfaction with normal body sizes or excessive weight gain (although it does seem plausible that the biological bases of body image in each of these cases should overlap...).

It's also quite possible that the even the original theory won’t pan out, or will turn out to be untestable – one of the problems with building a hypothesis around such an integrative brain area is that it’s extremely challenging to find a task that doesn’t activate it. And the resolution of current brain imaging techniques doesn’t really allow us to test whether different groups of neurons within the insula are doing different things.

True or not, though, the theory has some interesting implications.

For example, could you start to feel better about your body by doing things that encourage the integration of sense data into one’s internal body image?

Maybe it would help to spend some time lovingly gazing at your lumps and bumps in the mirror instead of frowning at them, avoiding them, dressing to obscure them, or trying to find an angle that makes them appear smaller than they actually are.

Alternatively, fans of yoga talk glowingly about how it makes them feel more ‘in their body’ – maybe this improves body image as much or more than the butt-tightening powers of the downward dog. Other forms of exercise like dance or weight-training could also have a helpful body awareness effect.

Or if none of that really appeals, what about more passive forms of body stimulation? In fact here’s a thought: maybe it doesn’t matter whether those fancy weight-loss rubs and potions you get at health spas actually help you lose weight – they could still make you feel better by making you get up close and personal with your physical self.

So if you’re feeling a little out-of-body I have a recommendation you might like to try: Book yourself a long, luxurious massage, and tell your therapist to spend extra time on all the areas you like the least. It’ll feel great. It’ll definitely activate your insula. And who knows, maybe afterwards you’ll love and accept your wobbly parts just a little bit more.

 

Susan Carnell, Ph.D., is a research psychologist at Johns Hopkins University, where she studies what drives some people toward obesity.

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