Obesity prevention efforts should begin as early as the age of two, when children reach a tipping point that could predispose them to obesity later in life, a new study has found.

Childhood obesity has grown into an epidemic over the past decade, reflected in soaring rates of type 2 diabetes and recommendations that paediatricians check toddlers for elevated cholesterol.

"This study suggests that doctors may want to start reviewing the diet of children during early well-child visits," said John W Harrington, a paediatrician at Virginia's Children's Hospital of The King's Daughters (CHKD).

"By the time they reach eight, they're already far into the overweight category, making treatment more difficult."

The study examined records of 111 overweight children from a suburban paediatric practice. All the children had their height and weight measured at least five times during paediatric visits. The average age was 12.

Children whose body mass index (BMI) exceeded 85 per cent of the general population were classified as overweight. Researchers charted the recorded body mass index of the children from infancy.

They found that the obese children had started gaining weight in infancy at an average rate of .08 excess BMI units per month. On average, they began this progression at three months of age.

Over half the children could be classified as overweight at two years old, 90 per cent before reaching their fifth birthday.

Vu Nguyen, a second year student at Eastern Virginia Medical School, CHKD's academic partner, said the results surprised him.

"I didn't think that obesity would start that early," said Nguyen, who presented the results on Friday at a paediatric research scholars programme.

Nguyen conducted the study with Harrington and Lawrence Pasquinelli, a paediatrician with Tidewater Children's Associates in Virginia Beach.