My son, Jason, 18, used to be a chubby teenager, but made the ugly-duckling-to-swan transformation around the age of 15, and is now a gorgeous, slim young man. Jason attributes his success to drinking gallons of water, but he clearly went much further. At every meal, he serves himself virtually half of what the other kids take, despite being the eldest.

He looks great, but we’re concerned about his paranoia of overeating. In my darkest moments, I wonder whether he is anorexic. He thinks skin-tight jeans make him look cool. Yet, how do we define cool, sexy or hot? How do we, as parents, navigate the question of image in today’s celebrity-obsessed world?

The science behind looking good and image for young people has two parts. While there is research confirming that being attractive counts in life (teachers, friends and parents judge physically attractive children as more competent, academically able, socially skilled and emotionally more adjusted), there is an even more substantial body of research to show that it is how a person feels and what they radiate to others that counts.

There are four dominant teenage myths surrounding image:

• It’s what you look like that counts.

Wrong. It is how a person feels that counts. Feeling comfortable and confident in one’s body leads to a positive body image. Research has shown that individuals who place an unusually high value on their own appearance, and who have a strong desire to be regarded as attractive, tend to have poorer mental and physical health than those who don’t. This is because body image is psychological and is influenced by an individual’s self-esteem, self-worth, perception of one’s body and how others may perceive it. It is not based on the truth, but on a perception of the truth, sensitive to mood swings, physical environment and experiences.

• If I look like my friends, I’ll be happy.

Wrong. What scientists call ‘social comparison’ is one of the quickest ways to lower self-esteem and damage self-confidence. People with an inherent tendency to judge what they look (and live) like compared with others can remain dissatisfied with their lot throughout their lives.

• If I’m beautiful, rich and famous, I’ll be happy.

Wrong. Research has found that children whose aspirations centre around money, fame and physical appearance tend to have poorer mental health than those who pursue goals such as developing close relationships or helping others. Those who feel the need to look good and be recognised have higher levels of depression and anxiety, and experience more physical symptoms, such as headaches, lack of energy and lack of vitality and enthusiasm.

• Girls care about their image more than boys.

Wrong. Girls talk about image more, but, on their own, boys have been shown to be more vulnerable about their looks than girls. The media and health agencies report that body-image issues have become more of a problem for teenage boys over the past decade.

So the real question for your teens is how to make a shift from being obsessed by their own anxieties to being someone who is more interested in other people. Not an easy task for them, or you as a parent to bring the idea across. And don’t despair if faced with another, ‘You don’t understand, Mum. Things are not the same now as in your day…’

More inspiration

Read: about the science behind image myths in Making Happy People by Paul Martin (Harper Perennial, £11.99)

Learn: about positive parenting at the Anglia Ruskin University: anglia.ac.uk/imapp

Photograph: Corbis