Researchers have found they can predict which babies will grow up to be obese.
The study showed that baby growth charts used at birth and up until the age of three can give an insight into how big a person will become later in life.
Babies' length and weight are measured from birth to the age of three, with the figures put on the growth chart as a percentile which shows how the child measures up with other youngsters of the same age and gender.
Doctors have now said that early weight gains should be looked at and not passed off as 'baby fat'.
Currently, toddlers in the 95th percentile or above are considered overweight and are more likely to be obese by the time they were 10, but the new research found that youngsters who moved more than two percentile points between birth and the age of two were also at risk of obesity.
The American study observed more than 44,000 babies over a decade.
Elsie Taveras, co-director of the One Step Ahead clinic - an overweight prevention programme at Children's Hospital Boston, said the findings gave doctors guidance to recognise when a baby is at a real risk of becoming obese later in childhood. She claims it could help stop the growing obesity epidemic in its earliest stages.
She said: "We shouldn't neglect these early gains and think that it's just baby fat, and that these children are going to grow out of it.
"Crossing two or more percentiles in weight-for-length should trigger a discussion between parents and their paediatric providers of what's contributing to the rapid gains.
"Infants are different than adults, and we wouldn't put infants on a diet, but we can detect some possible early risk factors that could be targets for counselling."
What do you think? Do you take any notice of the red book percentile charts?