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Effects of being underweight

Most people who have an eating disorder have an unremarkable body weight. Many will under-eat at times and binge eat at other times, so that weight is maintained overall within normal limits. However, some people with an eating disorder maintain extreme control over their eating, and become and remain significantly underweight. One of the diagnostic criteria for Anorexia Nervosa is a body weight less than 85% of the weight expected for a particular height. This is serious, as being underweight has significant physical, psychological and social consequences, and these consequences are often seen in people suffering from Anorexia.

Physical consequences of Anorexia include profound effects on the heart and the circulatory system due to loss of heart muscle, loss of bone density and muscle wastage, gastro-intestinal problems, hormonal problems including amenorrhea, and difficulties in the regulation of temperature and sleep. Psychologically, mood is generally low, and irritability and anger are exacerbated. There is a tendency to become socially withdrawn and inward-focused, and people who are underweight have an increased need for predictability and routine, and have difficulty being spontaneous. Thinking becomes rigid, and concentration and decision-making capacities are markedly impaired.  Preoccupation with food is usually intense, with almost constant thoughts about food and eating, such that it is common for underweight people to become very interested in cooking, recipes, cookery shows and so on. There is likely to be a corresponding decrease in engagement with previous interests and hobbies. Obsessiveness increases, with people becoming inflexible in their routines, particularly around food. There may be rituals around food preparation, the order or way in which food is eaten and the timing and circumstances of meals. People often need to eat alone, and food may be eaten very slowly.

Being under-eating causes many serious psychological and physical effects

The Minnesota Starvation Experiment


An important study of the effects of starvation has had a profound impact on our understanding of the behavioural and psychological changes we see in people with Anorexia.  This study was conducted in the early 1940’s and has subsequently been called the Minnesota Starvation Experiment. As Allied forces moved across German-occupied Europe, they encountered starved and emaciated civilians, many of whom had survived largely on bread and potatoes. As little was known about the effects of starvation or how to deal with the re-feeding of these people, a study was conducted in which 36 psychologically healthy young volunteers were subjected to a six month period of semi-starvation, followed by a three month re-feeding period. During the starvation period the men were given about half the calories needed for weight maintenance, and most lost about 25% of their original body weight.

The physical, social and psychological effects of the starvation on participants were studied in great detail, and reported in a two-volume text called The Biology of Human Starvation. The participants developed an intense preoccupation with food, with most of their thoughts oriented towards what and how they would eat. Concentration, judgement and alertness were significantly impaired. Eating became extremely slow, with unusual concoctions and heavy use of condiments, caffeine and chewing gum. Desire for food was intolerable for some, and binge eating occurred. The men became more depressed, irritable, angry and anxious, and sociability markedly decreased, with the men becoming withdrawn and socially isolated. During the re-feeding phase the men had difficulty regaining control of their eating, and struggled to identify whether they felt hungry or full.  For the majority of participants their eating behaviour did not return to normal until they had been at their pre-study weight for several months.

Clearly, as the participants in this study were psychologically and physically healthy prior to the experiment, all the behavioural and psychological features seen in the participants were direct effects of the starvation itself. The implications of this study for understanding the symptoms of Anorexia are clear: The behaviours and psychological changes that occur in people with this illness are direct results of the low weight, rather than being part of the illness itself, and therefore will begin to resolve once normal body weight is restored. The behaviours and characteristics shown are not indicative of peoples’ true personalities, which are in fact effectively masked by being underweight.

Weight restoration is essential


It is therefore clear that initially the primary goal of treatment for an underweight person with an eating disorder is weight restoration. Many of the features of his or her underweight behaviour and apparent personality change will gradually disappear as normal weight is restored. As found in the Minnesota study participants, the body does not immediately return to being able to regulate food intake on its own, but consuming a well-balanced and nutritionally complete diet, spread regularly throughout the day, encourages the body to re-establish normal weight maintenance mechanisms. It is very important for weight to be fully restored in order to reverse the starvation effects. If only partial weight regain occurs, the effort applied to achieve that weight gain will not be matched by equivalent improvements in mental and physical health.

It is often difficult for an underweight person to engage with treatment initially because many of the effects of being underweight keep a person “locked-in” to the eating disorder, creating vicious circles that maintain the problems. For example, the rigidity of thinking leads to difficulty making decisions or changes; the obsessional, inflexible approach to life makes it difficult to imagine eating or living differently; the social withdrawal reduces engagement with others and lowers mood; the preoccupation with food makes it difficult to consider engaging in other aspects of daily life. Please review the article Cognitive Behavioural Therapy for Anorexia Nervosa for more information about these kinds of vicious cycles that maintain the eating disorder. Support from others is likely to be centrally important in helping get through the weight-restoration stage of recovery. Once the effects of starvation have been reversed, other psychological factors that contributed to the development and maintenance of the eating disorder may need to be addressed, and areas of life which have been neglected will be re-developed.

I understand that if you are underweight and under-eating you may feel very fearful of  weight gain, but it is extremely important that you see your doctor and have a thorough medical assessment. I encourage you to contact me at Eating Disorders Brisbane, so that we can discuss your difficulties and fears and explore treatment options.

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