When you think of a person with an eating disorder, you might imagine someone who's painfully thin and unhealthy looking. But the truth is in many cases, you can't tell if someone has an eating disorder simply by looking at them.

If you're concerned someone you know may have an eating problem, there are lots of other signs to look out for. The good news is eating disorders can be treated successfully, and people can recover fully from them. The important thing is to get treatment and support as soon as possible - the earlier someone is diagnosed and treated, the more likely they are to make a full recovery.

The most common eating disorders are anorexia, bulimia and binge eating. These are serious mental illnesses that, according to the charity Beat, affect 725,000 people in the UK. Young women aged 12 - 20 are most at risk, though men and boys make up 15 - 20% of cases.

As for the causes of eating disorders, these can be a complex mix of genetic, biological and environmental factors, often combined with a trauma or life event that triggers the disorder. Some of these factors include having a family history of eating disorders or mental health problems, being under lots of stress and having an obsessive personality - including being a perfectionist - or low self esteem.

Symptoms of eating disorders

It's often difficult to know whether or not someone you know has developed an eating disorder. So here's what you should know about them:

Bulimia

According to Beat, bulimia is the most common eating disorder. Those who are affected become trapped in a cycle of bingeing - where you eat large quantities of food at the same time - and purging, which is when you make yourself sick or take laxatives to prevent putting on weight and because you feel guilty or ashamed about bingeing.

What are the signs?

People with bulimia often have a distorted view of their weight or their body shape. They may seem low, depressed, anxious and upset, and may have sudden mood swings. They may often eat in secret - or disappear soon after eating - and crave unhealthy foods when they binge. They may also exercise excessively to counteract their bingeing.

Many people with bulimia don't experience any significant weight changes (though this can happen). But they may get sore throats if they make themselves sick regularly, or develop irritable bowel syndrome (IBS) from using laxatives too often. They may also complain about being tired all the time or about having stomach or digestive problems.

Anorexia

Around 10 percent of eating disorders are caused by anorexia, says Beat. People with anorexia tend to have a low body weight and - through dieting, vomiting, using laxatives and/or exercising excessively - don't give their bodies what they need to produce energy or to stay healthy. According to the mental health charity Mind, anorexia isn't always about slimming and dieting, but can often be linked to very low self-esteem, negative self-image and feelings of distress.

How to spot it:

Someone with anorexia may eat hardly any food or even stop eating altogether. Because they're usually underweight they may feel cold and weak, and find it hard to concentrate or feel dizzy. Along with severe weight loss their hair may start to thin or fall out, they may feel frequently irritable or moody, and they may wear baggy clothes to hide how much weight they've lost.

Despite the fact they're underweight many people with anorexia may still believe they're fat. They can also take great efforts to hide their eating behaviours from those around them. People with anorexia may also often feel anxious and depressed, and may shut themselves off from the world.

Binge eating disorder

Binge eating affects men and women equally and tends to be more common in adults than younger people. It involves eating very large quantities of food at the same time. If someone binges at least once a week over a period of 3 months or more, they could have binge eating disorder.

According to Beat, binges are usually planned like a ritual and can involve special binge foods, usually eaten in private. But because they have little to no control over their eating, those affected can feel guilty or disgusted with themselves. This can lead to low self esteem, lack of confidence, depression and anxiety.

How to spot it:

Many people with binge eating disorder are overweight or obese as opposed to being very thin. They are obsessed with food and often eat without thinking - including when they're not hungry - and tend to choose foods that are high in sugar, fat or salt. Typical comfort eaters, they turn to food when they feel stressed, upset or unhappy, or when they want to suppress feelings they don't want to deal with. As a result they can become even more stressed, as well as feel embarrassed, worthless and unhappy about the way they look.

How to offer help

If you suspect someone you know has an eating disorder - or any kind of unhealthy relationship with food - offering your support without being judgmental or argumentative could make a big difference to them. According to Beat, people who have recovered from an eating disorder often say how important it was to have unconditional love and support from those who care about them - even when, looking back, they knew their behaviour was difficult to understand.

When you first bring up the subject of your worries to them, it's a good idea to know what you're going to say beforehand. Avoid talking about food, dieting or losing (or gaining) weight. Try to talk more about what they're feeling, rather than what they're doing or how they're behaving.

Find a quiet place for a chat where you won't be interrupted, and tell them you're concerned about them - that you've noticed changes in their appearance or behaviour - and that you want to help. Most importantly, stay as calm as possible, as it's likely they won't respond positively.

If the person you're worried about acts defensively, it's normal at this stage. But they'll know you're there for them when they're ready to talk again. When they do come back to you, let them know what professional help is available to them. Encourage them to see their GP, who can refer them to services that offer treatments such as counselling, nutrition advice and other specialist support. Tell them they may also be offered helpful medication such as antidepressants or other treatments for any underlying causes of their problems.

You can also refer them to organisations they can get help and information from, such as Beat, Anorexia and Bulimia Care, Mind, Mental Health Foundation and Royal College of Psychiatrists.

And remember, you can call us if you're worried about anything - we're here to help. Give us a call on +44 (0) 1788 556 366 for advice or information, or chat to one of our advisors online at any time of the day or night.