Published: 10/02/2005, Volume II5, No. 5942 Page 33

Being an uncle brings opportunities to paint myself as eternally benevolent - a role I seldom inhabit at work. My (infrequent) arrivals are invariably met with joy, not least because they signal presents, treats, and trips out. Together, we roar with laughter and sing our socks off.

My niece asks what it is like to be grown up. 'I wish I was 10, ' she told me last time I saw her. 'I wish I was 10 years younger', I say to her, but she is far too young to understand how significant that is for somebody racing through his 30s.

You can imagine the shock when a minor scuffle broke out recently over a large piece of chocolate. 'But I want it, ' cried my niece as I tried to prize open her hand. 'I'll be good, ' she pleaded.

I continued my attack, adamant that she had eaten more than enough. Tears followed: 'But, I've been good' she sobbed through snot and indignation. 'There will not be a tooth left in your head, ' I replied with little charm or wit, and an amazing resemblance to my own dear mother. 'Have a banana, ' I suggested. The look she gave me was stiffening.

I understood her feelings. I like chocolate. And I can just about remember being a child. And we had had a lovely time together, I felt like I had been hard on her (she had been well behaved). And I was upset that in behaving responsibly I had ruptured our relationship - if only for two minutes.

I was also interested in how she linked having a good time with excess. And how in curbing that excess I had spoilt the fun. And it was then that I realised something fundamental about health improvement.

Some people enjoy smoking. They might want to stop, but they like it.

Doing it brings personal pleasure and enables social interaction. It is part of their identity. Others love chocolate; they relish its tastes and textures. Their spreading middles might cause concern, but their love of chocolate continues. Others enjoy the taste of Sauvignon or the kick of a stiff vodka. And a growing number of people enjoy a diminished/ heightened sense of reality through taking drugs.

People do not overeat, drink, smoke, take drugs or have unprotected sex because they are bad for their health or because they make them feel bad. They do them because they feel good; they bring personal and social rewards.

Important stuff.

Changing behaviours is linked to increasing choices (access to fruit and veg, for example); some of it is about reducing choices (not selling fizzy drinks in schools). Much of it is linked to poverty.

But we have not got hold of all of it. There is a missing piece. We do not understand the rewards that engaging in pleasurable but unhealthy behaviours brings. I do not think we have even asked the question. Why do colleagues crowd together in the pouring rain to smoke? What triggers binge drinking in our cities? Why are some 15-year-olds taking cocaine? Why do we eat so badly? We know none of it brings good health. But we enjoy it!

We should step away from focusing endlessly on individuals and their personal challenges and get a clearer understanding of what leads us to do what we do collectively. Eating, smoking and drinking are often shared activities; they are social as much as individual. We should consider questions about poverty and access, as well as the social importance of pleasure, and its rewards. An effective assault on obesity, alcoholism and the rest will not exist until we do.

David Woodhead is deputy director of public health at Salford primary care trust and Salford city council. He writes in a personal capacity.