The increased risk of cardiovascular disease (CVD) seen in healthy men starts as early as the age of 19, say US scientists.
They also showed that the innate protection against CVD associated with females begins in puberty and fades after menopause.
The study focused on 507 children who were assessed from the age of 11 to 19.
BP, insulin sensitivity, BMI, blood glucose and cholesterol were all assessed at regular intervals.
Although puberty saw the percentage of body fat rise in girls and fall in boys, underlying predisposition to CVD was already becoming evident among males as young as 19.
Triglyceride levels rose, HDL cholesterol levels fell, systolic BP significantly increased and insulin resistance also went up in men by the end of their teenage years.
At the same time, girls had falling levels of triglycerides, rising levels of HDL cholesterol, a less steep rise in systolic BP and were showed less insulin resistance than males.
No gender differences between total and LDL cholesterol were found.
Lead researcher Professor Antoinette Moran, a paediatric endocrinologist at the University of Minnesota's Children's Hospital, said: 'Boys and girls have equal cardiovascular risk before puberty, but by the end of puberty boys have greater risk.
'This is somewhat surprising since it occurs at a time when boys are becoming less fat and more lean, and girls are accumulating body fat.'
It suggests 'factors other than body fat are contributing to cardiovascular risk,' said Dr Moran, adding that while oestrogen is a likely contributory factor, this is still to be proven.
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