An increased risk of cardiovascular disease is indicated in decreasing healthy years for obese young people.
Being obese has the potential to reduce a person's life expectancy by up to eight years and diminishes their number of healthy life years by up to 19, international researchers have found.
The effect of excess weight on years of life lostwas greatest for younger individuals and was mainly due to an increased risk of cardiovascular disease.
Meanwhile, Australian researchers have found programs to prevent young people becoming overweight or obese are failing, primarily because they are poorly designed and evaluated.
To measure the impact of obesity on life expectancy, Canadian researchers built a computer model that measured the increased risk of developing cardiovascular disease and diabetes in adults of different body weights.
They estimated overweight individuals, with a BMI between 25 and 30, could lose up to three years off their life expectancy, depending on their age and gender.
Obese individuals, BMI between 30 and 35, were expected to lose between one and six years, while very obese people could lose between one and eight years.
Using data from a major US health survey, the team also measured the impact of excess weight on an individual's healthy life years – years free of obesity-associated cardiovascular disease and diabetes.
The study, published in The Lancet Diabetes & Endocrinology journal, found being overweight or obese was linked with a two to four-fold loss of healthy life-years compared with total years of life lost.
Loss of healthy life-year is mainly due to the development of type 2 diabetes or cardiovascular disease at an earlier age so was most pronounced in very obese young adults, who lost about 19 healthy years.
Nutrition researcher Margaret Allman-Farinelli said young adulthood was the weight gain "danger" time because, on average, Australians aged 25 to 34 gain on 6.7 kilograms over ten years.
"Per annum, they gain more weight than any other adult group," said Professor Allman-Farinelli, from the University of Sydney's Charles Perkins Centre.
This was likely due to lifestyle changes such as joining the workforce and having to cook for themselves.
"The other thing that happens in young adulthood is the physical activity can start to drop off," she said.
But an analysis led by Professor Allman-Farinelli of trials designed to prevent weight gain in young adults found only 50 per cent helped participants control their weight in the short term.
The analysis, published in Obesity Reviews, found most studies failed to follow up participants' progress after six months, or report data such as cost or the ethnic and socioeconomic background of the participants that policy makers need to introduce programs into the community.
Professor Allman-Farinelli said more rigorous research was needed to identify programs that help young people control their weight because preventing weight gain was a better strategy than treating it.
"Once overweight, most people are on a trajectory of continual weight gain throughout their life," she said.