Diseases previously seen only in adults are now being diagnosed in hefty children, who are likely to also be overweight or obese as adults.
"Overweight and obese children bear near-term risks of developing Type Two diabetes, and ill health, heart attack or stroke before they are 65," said Janet Voute, chief executive officer of the Geneva-based World Heart Federation, on Monday.
The federation issued the warning before World Heart Day on 26 September, which is focusing on children, adolescents and heart disease.
Unhealthy lifestyles comprising high-calorie diets, dwindling exercise and hours spent in front of the television or computer have contributed to a surge in childhood obesity.
Poor diet and little exercise cause
obesity, leading to heart disease
Voute hopes that by making the link between children and heart disease and by showing how poor diet and lack of exercise in youth contribute to it, people will be shocked into doing something about it.
An estimated 10% of children or at least 155 million youngsters worldwide are overweight or obese, according to a report by the London-based International Obesity Task Force (IOTF).
"We must protect children from an environment that leads to heart disease by teaching lifelong healthy eating habits and limiting exposure to unhealthy food," said Sania Nishtar, chair of the federation's advisory board.
Voute believes parents, children and adolescents do not fully realise that the habits adopted at a young age could lead to health problems in adulthood.
"Lifestyle habits are set early and that is why the World Heart Federation is calling attention to that issue," she said.
"Lifestyle habits are set early and that is why the World Heart Federation is calling attention to that issue"
World Heart Federation chief
Voute called for a revamp of nutrition in schools, including a rethink of what is served in cafeterias and sold in vending machines. Policy makers also need to increase physical activities in schools.
The federation also warns that tobacco is threatening the health of children's hearts.
Globally, nearly 25% of students smoke and half of children worldwide are subjected to passive smoking by living with a smoker.
Children regularly exposed to second-hand smoke have a 25% increased risk of both lung cancer and heart disease and an 80% raised risk of stroke, according to the federation.