Body image is a term which may refer to our perceptions of our own physical appearance, or our internal sense of having a body which is constructed by the brain. Essentially a person's body image is how they perceive their exterior to look, and in many cases this can be dramatically different to how they actually appear to others. Negative feelings towards a person's body can in some cases lead to mental disorders such as depression or eating disorders, though there can be a variety of different reasons why these disorders can occur. Within the media industry there have recently been popular debates focusing on how Size Zero models can negatively influence young people into feeling insecure about their own body image. It has been suggested that size zero models be banned from cat walks. Many celebrities are targeted by the media due to their often drastic weight loss and slender frames, examples of such personalities would be member of the Spice Girls and wife of L.A Galaxy Footballer David Beckham, Victoria Beckham, famous socialite and daughter of Lionel Richie, Nicole Richie and ex Destiny's Child member turned solo singer and Actress Beyonce. Other controversial thin celebrities include British Super Model Kate Moss. Some examples of celebrity men targeted in a similar fashion can be found, but the media seems to focus principally on the effect that the Size Zero phenomenon has on young women.
Body Image and Physical Appearance
Body image is often measured by asking the subject to rate their current and ideal body shape using a series of depictions. The difference between these two values is the amount of body dissatisfaction. Monteath and McCabe found that 44% of women express negative feelings about both individual body parts and their bodies as a whole. Psychology Today found that 56% of the women and about 40% of the men who responded to their survey in 1997 were dissatisfied with their overall appearance.
The desire to lose weight is highly correlated with poor body image, which typically means that more women have a poor body image than men. Susan Kashubeck-West, Laurie B. Mintz, and Ingrid Weigold report that the sex differences in body image disappear when we consider only those people who are trying to lose weight.
Our life orientation also shapes how we feel about our bodies. Women who self-identify as feminists view their body more positively than those who do not consider themselves feminists, even though there was no difference between the groups in average body weight. Exercise habits, sexual experiences, and mood also influence the feelings people have toward their bodies.
Men's body image is a topic of increasing interest in both academic articles and in the popular press. Current research indicates many men wish to become more muscular than they currently perceive themselves to be, often desiring up to 26 pounds of additional muscle mass.
The desire for additional muscle has been linked to many men's concepts about masculinity. A variety of research has indicated a relationship between men's endorsement of traditionally masculine ideas and characteristics, and his desire for additional muscle. Some research has suggested this relationship between muscle and masculinity may begin early in life, as boys' action figures are often depicted as super-muscular, often beyond the actual limits of human physiology. 
This desire for additional muscle has been given various nicknames, including "The Adonis Complex", "Bigorexia", "Reverse Anorexia", and "Muscle dysmorphia". Muscle dissatisfaction has been linked to low self esteem, personality disorder  and is related to the use of muscle-building supplements and anabolic steroids.   As such, men's body image dissatisfaction represents a substantial concern to public health researchers.
Body Image and the Brain
Definition and Origin
According to Vilayanur S. Ramachandran of the University of California, San Diego, the nature of self has five defining characteristics. One of them is the sense of embodiment and ownership of a body. Although we do in fact have a body, the brain is responsible for the construction of a "body-image," a term introduced in the writings of neurologist Henry Head (which also has been used interchangeably with the term body-schema.) Your sense of having a body involves the visual system, the vestibular system, and proprioception; the sense of body position and movement (a term coined by Charles Scott Sherrington in his published work entitled, The Integrated Action of the Nervous System.) Proprioception correlates with dynamic body maps in the somatosensory, motor, and parietal cortices. Most notable is the primary somatosensory receiving area (S1) in the somatosensory cortex, where the sensory homunculus or "little man" resides. The neurons in this region are responsible for cutaneous (skin), visceral (organ), and proprioceptive sensation, as they fire to represent each part of your body--from the genitalia to the internal organs--with the help of sensory input that travels from peripheral nerves, through the spinal cord, and into the brain.
Ablation of those sensory nerves that carry sensory input from proprioceptors to the brain, results in a loss of proprioception. A person may experience such a loss in certain limbs, or throughout their entire body. In Oliver Sacks book, The Man Who Mistook His Wife for a Hat, he describes a patient named Christina who suffered from a selective neuritis--an infection in her spinal fluid that disconnected her entire body from the parietal cortices in her brain, causing a total loss of proprioception--and thereby a sense of disembodiment. Christina would flail and overshoot her limbs. Her body flopped around like a rag doll. Standing or sitting straight was nearly impossible for her.
Many amputees who have lost limbs, continue to sense the presence of them, as the body-image remains intact. Even those born without arms or legs, experience such phantoms. Often, the presence of these phantoms are so convincing, patients may step out of bed onto phantom legs or feet, or pick up cups with a phantom hand (Ronald Melzack, 1992-2006). A phantom limb is integral to wearing a prosthetic, in which the phantom fits like a glove. The body-image of the missing limb must be present, otherwise a prosthetic cannot be used effectively.
There are many types of phantoms. Some are paralyzed; frozen in unusual positions. Many phantoms are like photocopies; exact replicas of the missing limbs. Others are grossly distorted and disproportioned--they may even be disconnected from the rest of the body and dangle in mid-air. Some disappear, only to be resurrected decades later. Interestingly, a women may have a phantom penis with phantom erections. While the overall sex of a human being is determined by DNA, it is possible that the sex of the brain itself is determined by the hormones an embryo is exposed to while in the womb. Nonetheless, a man may have a female brain, and a woman may have a male brain. This phenomenon may explain transsexualism.
The somatosensory system has been known to be involved in phantom limb syndrome. According to V.S. Ramachandran, motor signals contribute to phantom limb phenomenon as well. The motor cortex is primarily responsible for voluntary movement. But when motor signals are sent to muscles, a duplicate signal is sent to the parietal lobes as well in a feedback loop, thereby eliciting a sense of proprioception in the missing limbs.
The body-image also emerges from the convergence of multiple senses (i.e. proprioception and vision) in the angular gyrus and supramarginal gyrus. The body-image can detach from the physical body, and take on a phantom existence. Note that electrical stimulation of the angular gyrus causes an out-of-body experience, a decoupling of vision and proprioceptive sensory experience.
Also, some patients with anosognosia, usually left-side hemiplegics who have suffered from a stroke, experience a disassociation with their paralyzed limbs. Some may be convinced that their paralyzed leg for example, is not really theirs--perhaps the leg of a stranger. They will assert that their real leg has disappeared, and in this conclusion, attempt to shove or kick their own leg out of bed. This kind of anosognosia involves lesions on the right side of the brain--notably the somatosensory and parietal cortices.
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Olivardia, R., Pope, H.G., Borowiecki, J.J., & Cohane, G.H. (2004). Biceps and body image: The relationship between muscularity and self-esteem, depression, and eating disorder symptoms. Psychology of men and masculinity, 5, 112-120.
Pope, H.G., Phillips, K.A., & Olivardia, R. (2000). The Adonis complex: The secret crisis of male body obsession. Sydney: The Free Press.
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Ramachandran, V.S. and Rogers-Ramachandran, D. “Its All Done with Mirrors.” Scientific American Mind, August 2007: 16-18
Ridgeway, R.T., & Tylka, T.L. (2005). College men’s perceptions of ideal body composition and shape. Psychology of men and masculinity, 6, 209-220.
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- The influence of societal factors on female body image. J Soc Psychol. 1997 Dec;137(6):708-27
- Psychology Today: Body Image Poll Results
- Separating the effects of sex and weight-loss desire on body satisfaction
- Psychology Today: Body Image Poll Results
- Pope, Phillips, & Olivardia 2000
- McCreary, Saucier, &Courtenay 2005; Kimmel & Mahalik, 2004
- Pope, et al. 1999
- Olivardia, et al. 2004
- Davis, Karvinen, & McCreary, 2005
- Olivardia, et al. 2004
- Ridgeway & Tylka 2004
- Vilayanur S. Ramachandran, 2007