Health: My God, he asked for carrots]: Eileen Fursland offers parents tips on weaning a child off sweet foods

Who hasn't resorted to bribing a child at some time? 'Just a spoonful of carrots and then you can have some lovely pudding . . .' But, says an American psychologist, bribery is one of several mistakes parents make when it comes to persuading children to eat 'healthy' food.

As evidence grows of the power of diet, especially in early life, in protecting against disease, the pressure on parents is even more intense. Yet it is 'eating up their greens' that children resist most.

But the promise of pudding only makes a child dislike vegetables more while increasing his craving for ice-cream, claims Dr Leann Birch, professor of human development and nutritional sciences at Pennsylvania State University.

Here, a survey commissioned for a current Channel 4 series, Eat Up, showed that more than half of the 250 schoolchildren who completed a food diary for a day ate no vegetables at all and very little fruit, and that most children will not eat vegetables voluntarily. (Brussels sprouts were particularly despised). A survey by the Henley Centre in June found that nearly four out of 10 children refused to eat the same meals as their parents.

Dr Birch and her team have investigated common practices in feeding children to gauge their effect on food-acceptance patterns. She has formulated an approach for parents to try and says early experience is crucial.

The first rule bans rewards of any kind. Sweet foods and praise for eating a hated item are out. In one study children were given yoghurt drinks, a food about which initially they felt neutral. The children who were rewarded for drinking eventually came to like the yoghurt less than those who had not been rewarded.

'This is consistent with a lot of psychological literature,' Dr Birch says. 'For many activities, if you take something people like doing, and pay them to do it, they begin to like it less.'

Because of our innate preference for sweet things, vegetables have little going for them as far as children are concerned. Yet many foods needed for a nutritious diet are not sweet, so children must learn to like them. Unwittingly, Dr Birch says, many parents hinder this process.

'Parents tend to give up too soon. Children are naturally suspicious of new foods and, for a baby, everything is new. Unless that food is sweet, it's unlikely to be readily accepted.'

Her research shows that if you offer a new food often enough the child will accept it. It may take eight to 10 exposures to the food before that happens.

'Parents must not see a child's initial rejection as a fixed dislike. It's asking a lot of a parent to present a food many times and see it rejected, but that's what you have to do.'

Rule No 3 is not to give the child too much to eat. 'The amount many parents put on their child's plate is inappropriate. People tend to think a two-year-old child should eat half a cupful of peas. In fact, he would need about a quarter of that amount.'

Children are good at heeding the physical signals that tell them how hungry they are and when they are full. Dr Birch's research shows that, given free choice, children control their food intake far better than adults. She offered children either a high- or low-calorie snack and, soon after, a meal. Even pre-school children controlled their intake almost calorie for calorie by eating less after the high-calorie snack and more after the low-calorie snack.

This explains why children who have snacks and drink between meals are more fussy at mealtimes.

In the same experiment, adults ate the same amount of the meal regardless of whether they had had a high- or low-calorie snack beforehand. 'It's easy for adults inadvertently to turn off this sensitivity in their children. If you talk to children who are eating about how whether they are getting full, they continue to do well. But if you say: 'Clean up your plate' or 'if you eat it all, we'll give you ice-cream', the children's responsiveness to energy needs disappears.'

Most experts agree that when faddy eating becomes a family issue, part of what is going has little to do with nutrition. It is more a power struggle.

'We've been doing work that suggests parents who are overweight are particularly controlling of their children. They assume their children can't control their intake and start restricting food or pushing it. This produces children who aren't sensitive to their internal cues of hunger and satiety, possibly perpetuating these familial patterns of obesity.'

David Booth, professor of psychology at the University of Birmingham, advises parents against getting into battles over food. 'It is important not to screw up the personal relationship between parent and child. The best advice is not to get over-fussed, as long as the child is eating enough to grow and be healthy. Children can suffer from food allergies and intolerance and even anorexia, but these cases are much rarer than people believe. If the child is losing weight, specialist advice should be sought - but pickiness is not the same thing.'

Not everyone takes this low-key line. John Pearce, professor of child and adolescent psychiatry at Nottingham University, claims success for his more drastic approach. In this, the child is refused all food other than the one the parent wants him to eat for 48 hours. 'Make sure your child isn't having snacks or drinks between meals, and limit milk. The trump card is hunger. If he doesn't eat the food you've provided, he doesn't get anything else,' Professor Pearce says.

The advice to parents to keep serving the food, but not to push the child to eat it, worked well for one mother who had spent months making faces out of vegetables and dyeing them all the colours of the rainbow to get her child to try them. 'I would have been so happy if he had eaten just one pea,' she said.

After two weeks of taking the laissez-faire line, 'Dale asked for a carrot. He tried it. He asked for another. I was flabbergasted.'