Kindergarten kids are heavier and on their way to becoming overweight and obese in the years to come, a new study finds.

“It’s not just kids who are already overweight getting more and more so, there is an entire shift. Even those who are normal weight are gaining weight,” said lead study author Ashlesha Datar, senior economist at RAND Corp. in Santa Monica, California.

Kids today are heavier than those brought up in the 1970s and 1980s, the study says. Nearly 40 per cent of kindergarteners had a body mass index (BMI) in the 75th percentile or above, up from 25 per cent in the 1970s and 80s when the growth charts were first developed.

A percentile shows how boys and girls compare to children of the same age and gender.  For example, a girl in the 70th percentile weighs more than 70 per cent of girls her age but weighs less than 30 per cent.

A BMI in the 70th percentile is at the upper end of the normal range, which means that these kids may be overweight or obese if their habits don’t change.

The number of overweight and obese children has also increased.   About 28 per cent of children in the current sample had a BMI classified as overweight, compared to ten per cent of earlier generations.

Childhood obesity more than doubled in the same period, with 12 per cent of kids classified as obese, compared to five per cent in the 70s and 80s.

When do kids gain the weight the most?  Between the age of five and eight, when the proportion of kids in the 75th percentile or above hit almost 48 per cent.

Experts warn the findings show that it’s important to start better eating and exercise habits as early as kindergarten possibly.  The programs should include kids who are normal weight.