Anorexia vs bulimia: how the two eating disorders differ

Anorexia nervosa and bulimia nervosa are the best known eating disorders. The NHS describes anorexia as an eating disorder and serious mental health condition in which people try to keep their weight as low as possible, often with a distorted image of their body that leads them to think they are fat even when they are underweight. It describes bulimia as an eating disorder and serious mental health condition that can affect anyone.

Both involve an intense preoccupation with food, weight and body shape. Beat, the UK eating disorder charity, says people with bulimia place strong emphasis on their weight and shape and may see themselves as much larger than they are, and that people with anorexia may have a distorted image of themselves and a deep fear of gaining weight. The differences are in the pattern of behaviour and, often but not always, in weight.

The table summarises how the NHS and Beat describe each condition.

The conditions are not always separate. Beat describes two subtypes of anorexia nervosa. In the restricting subtype, people severely restrict the amount and type of food they eat. In the binge-purge subtype they also restrict, but may do lots of exercise, make themselves sick or misuse laxatives, and may experience cycles of bingeing and purging.

Beat says the binge-purge subtype can sometimes be confused with bulimia nervosa, and that the main difference is that people with the anorexia binge-purge subtype continue to restrict their intake overall and are typically underweight, whereas people with bulimia are usually within or above a healthy weight range. It stresses that both are serious and deserve support.

Beat also describes atypical anorexia, where symptoms do not match every diagnostic criterion, for example because the person is at a weight considered "normal" for their age, sex and development. This is classed as a type of other specified feeding or eating disorder (OSFED) and is described as just as serious as anorexia nervosa. Beat says atypical anorexia can develop both into and from anorexia nervosa, so the picture can change over time.

The NHS lists signs of anorexia that include, for adults, an unusually low body mass index, missing meals or eating very little, thinking about food a lot, avoiding foods seen as fattening, believing you are fat when you are a healthy weight or underweight, periods stopping, and physical problems such as light-headedness, hair loss or dry skin. For under-18s it refers to weight and height lower than the minimum expected for their age.

For bulimia the NHS lists binge eating and purging, fear of putting on weight, being very critical about weight and body shape, excessive exercise, mood changes, planning binges, guilt and shame, secretive eating, and avoiding social activities involving food. Physical signs include tiredness, trouble sleeping, weakness, a sore throat from being sick, bloating or tummy pain, puffy sides of the face and irregular or stopped periods.

The NHS advises that if you are worried about someone else, you should encourage them to speak to their GP, and that signs in someone else can include eating lots of food over a short period, hiding food or eating in secret, going to the bathroom a lot after eating, and exercising excessively or obsessively.

The NHS says long-term anorexia can lead to severe problems linked to malnutrition, including muscle and bone problems such as osteoporosis, fertility problems, heart and blood vessel problems such as an irregular heartbeat and low blood pressure, brain and nerve problems, kidney or bowel problems, a weakened immune system or anaemia. It says anorexia can also put your life at risk and is one of the leading causes of deaths related to mental health problems, whether through physical complications or suicide. Most of these problems usually begin to improve once food intake improves.

For bulimia the NHS lists teeth problems because stomach acid damages enamel, damage to the lining of the throat, irregular or absent periods, seizures, heart or kidney problems, bowel problems including constipation, and weakened bones. It says that without the right support bulimia can sometimes be life-threatening.

For either condition the NHS advises seeing a GP as soon as you can, even if you are not sure. The GP will ask about eating habits and how you feel, may weigh you (for bulimia the NHS notes you can tell your GP if you do not want to know your weight), check your physical health, and refer you to an eating disorder specialist or team if they think you may have an eating disorder.

For anorexia, adults should be offered a talking therapy, commonly CBT, Maudsley anorexia nervosa treatment for adults (MANTRA) or specialist supportive clinical management, and under-18s should be offered family therapy and perhaps CBT or adolescent-focused psychotherapy. For bulimia, treatment can last several months or years and may include talking therapies, usually starting with a self-help booklet or online programme, medicines such as antidepressants if there is a linked condition like anxiety or depression, and support from a dietitian. The NHS says some people need hospital stays if they have serious health problems or are at risk of self-harm or suicide.

Beat, the eating disorder charity, runs a helpline and support services for people with any eating disorder and for families, and the NHS lists it as a source of confidential advice.