By Sandra Blakeslee and Matthew Blakeslee
Authors of The Body Has a Mind of its Own
Why do you still feel fat after losing weight? Why is yo-yo dieting so prevalent? Are anorexics really being honest in their heart of hearts when they gaze in a mirror at their scrawny, starving bodies and insist they are grossly fat?
You’ve heard all the standard-issue answers to these questions. You still feel fat because your body’s natural set point is out of whack. You yo-yo diet because you simply fell off the celery wagon into a tub of deep fry. Anorexics had absurdly narrow beauty standards flash-burned into their psyches by a relentlessly youth-centric pop culture abetted by shallow, distant parents â€“ that, or they’re just plain drama queens.
But a very different set of answers can now be glimpsed in new findings about how your brain maps your body, the space around your body, and your social world. The science of “body maps” reveals how mind and body interact to create your sense of being a whole, autonomous, embodied individual. It also shows how easily that sense can be discombobulated, and how you can bring it back into balance when it falls out of sync.
To grasp the concept of a body map, ask yourself, how do you know your hand belongs to you? How do you know where your body begins and ends? You might answer, “Well, I just know. Because it’s mine. I can feel things through it and command it to move how I want.”
But this deep-seated sense of control and ownership doesn’t just pop into your mind by magic. It arises from a symphony of coordinated activity between various maps of your body â€“ literal maps, not unlike road maps â€“ that are etched into the thinly layered surface of your brain.
For example, your brain has a fundamental touch map, with swaths of tissue dedicated to mapping touch sensations from each finger, hand, cheek, leg, arm, foot and toe, as well as your tongue, teeth, throat, genitals, and every other body part you can name. When someone claps you on the shoulder, you know it was your shoulder and not your neck or your arm because the cells that make up your shoulder map become active while the cells in your neck and arms maps stay quiet.
Right next to your touch map is a second fundamental map which handles not sensation but motor activity (a fancy term for movement). You can choose which finger to wiggle because each finger is represented separately in your motor map. The cells in the chosen finger map fire, sending commands down to your muscles to make the intended movement happen.
Beyond these two basic maps you have many others that map your muscles, joints, bones and viscera, as well as your immediate action plans, your goals and intentions, and your body’s vast library of so-called “muscle memories.” Your brain also maps the space around your body. Wave your arm up over your head, out to your side and down to your leg. Each point of that space is mapped inside your brain in relation to your body.
In other words, your brain contains a sprawling network of body maps that are always interacting â€“ the vast majority of it occurring outside of consciousness â€“ to give you that deceptively self-evident sense that, yes, your hands, feet, mouth and every other part of your body, inside and out, belongs to you, is accurately understood and perceived by you, and is at your free will’s beck and call.
This view of yourself isn’t entirely unfounded, but it glosses over what is happening under the hood — details that can have big consequences for leading you down the garden path into denial, delusion or unwarranted self-scorn.
To grasp why you may still feel fat after losing weight, you need to consider two particular body maps that can strongly conflict, giving you the sense that you are doomed to be fat. One maps the internal felt position of your body. The other is a distributed map concerning your beliefs about your body.
The first map, called the body schema, is based on signals from your muscles, bones, tendons, skin, and joints that tell your brain where you are located in space and how your body is configured. This map is dynamic, meaning it changes from moment to moment as you move around in the world. It also contains memories of how your muscles engage to produce different actions and postures. And it incorporates your ability to balance your body against the force of gravity.
When you lose a significant amount of weight, your body schema will update itself accordingly. The unconscious signals coming up from your body into your brain reflect a thinner, lighter, more flexible self. Your clothes (which are also incorporated into your body schema â€“ but that’s another story) fit differently. Your belt is a notch or two smaller. Your old jeans are loose.
And yet, like millions of others before you who have successfully toned up and slimmed down, you may still feel fat. The signals from your thinner body schema are not percolating all the way up into consciousness. Sure, you notice you look somehow thinner in the mirror, a little bit, maybe, but that is not how you feel. You feel fat, and you continue to see all your former pudginess because another body-mapping system is trumping your schema. It is called the body image, and it is composed of a more widely distributed collection of mental images, memories, beliefs and opinions about your body.
Your body image stems primarily from experiences in childhood and adolescence. Like political and religious beliefs, your beliefs about your body â€“ I am fat and unattractive; my body is disgusting and frightening; and so on â€“ are built up from what you see around you, what people who are close to you say, and how people in your society behave. For example, a young girl who is teased mercilessly about being flat chested may never think of her body as being normal. A little boy who is teased for having pop-out ears may never, despite later changes in proportions to his face, stop seeing a freak staring back at him through the looking glass.
Thus your body image, held in memory and language circuits throughout your brain, can easily overwhelm your slimmed-down body schema. You get discouraged and regain the weight you can’t stop believing in anyway. Your yo-yo dieting begins another new cycle.
Fortunately, there are ways to redress this schema-image disconnect. For example, wobble boards used by personal trainers bring your body schema into sharp relief, forcing you to attend to the signals you may normally tune out because they frighten or discomfit you. Another route is to go see a somatic psychologist, a therapist who guides patients to stay bodily self-aware and viscerally attuned as they talk about their troubles.
And anorexics? Recent research shows that people with this deadly condition may abnormally map their bodies and the space around their bodies, especially with regard to vision and touch. This is why anorexics literally see themselves as fat when looking in a mirror. Give an anorexic a pair of calipers and ask her to open it to equal the thickness of her arm, and she will open it to the width of Popeye’s biceps. And she is not making it up. Her brain maps have become miswired. With this new brain-based understanding of anorexic sensory misperception, new therapies are being tested to reconnect abnormal body maps. If they end up working, lives will be saved.
copyright 2007 Sandra Blakeslee, Matthew Blakeslee
Sandra Blakeslee is a regular contributor to The New York Times who specializes in the brain sciences. She has co-written many books, including Phantoms in the Brain with V.S. Ramachandran, On Intelligence with Jeff Hawkins, and Second Chances: Men, Women, and Children a Decade After Divorce with Judith S. Wallersein. She is the third generation in a family of science writers.
Matthew Blakeslee is a freelance science writer in Los Angeles. He represents the fourth generation of Blakeslee science writers.