He told a national conference on children's health: "For children born in adversity school education offers an escape which benefits all." But politicians and professionals needed "a broader education".
Any notion they may have that ill health was a problem simply to be laid at the door of the doctor had to be challenged.
"The diagnosis is social and economic, and the treatment is social and economic," he said. They also had to recognise that the health of children was "the bedrock on which all our lives are built. It is the determinant, not only of our health as adults, but of the prosperity of individuals and communities. "
Professor Watt, who holds the Norie-Millar chair of general practice at Glasgow University, pointed out how death rate patterns in various diseases had been "established by a succession of cohorts of children throughout this century. Adverse risk factors established early in life cast a long shadow over our health as adults," he emphasised.
Increases in recent years in suicide, violent crime and drug-taking rates in men, and higher stress and anxiety levels in women, were all signs of "a deep malaise in society" - and signs of problems which, in turn, affected the health and development of young children.
Professor Watt praised early years educational intervention initiatives pioneered in North America which had resulted in adults with a host of educational, economic and social advantages.
"Investing in children is an important part of the economy," he emphasised. Nursery, day care and playgroups were asked to take the lead in promoting healthy eating and drinking for the under fives by using special nutritional guidelines which have been produced by Forth Valley Health Board and Central Healthcare NHS Trust along with Clackmannanshire, Falkirk and Stirling councils.
The pack was "an important step forward towards an overall improvement in our children's health and, consequently, in their future health as adults," said Morag MacKellar, dietetic adviser for Forth Valley and head of nutrition and dietetics at Central Healthcare.
It recommends that pre-five service providers restrict the choice of drinks at snack and lunch times to milk and water - to the exclusion of fruit juices and soft drinks. But children should be given a wide choice of foods "so they realise it doesn't always have to be a bag of sweets they eat," she said.
The guidelines also aim to encourage under-five services to adopt a "whole environment approach to food". Youngsters should therefore be encouraged to develop their manual skills through preparing snacks, Ms MacKellar said. They should also learn about personal and food hygiene.
Delegates at the conference, organised by Scottish Early Years Forum, also heard about a variety of models in the provision of childcare services. NCH Action for Children has recently combined with Moray Council in devising a new integrated strategy - a move which breaks "the traditional mould of a local authority commissioning services from a voluntary sector body," John Sullivan, senior social work manager for Moray Council, observed.
"The idea has been to provide an improved range of services for children and families within a small local authority," he said.
Education and health services had also been involved in devising the strategy. "It would be wrong to be complacent about children's health in rural areas because poverty is more easily masked," he added.