Babies fed enriched bottle milk are more likely to be obese by the age of five, claim researchers.
A study shows faster weight gain in infancy can programme babies for life, putting them at risk of health problems ranging from heart disease to diabetes.
It found healthy babies given formula milk enriched with protein, vitamins and other nutrients had 22 percent to 38 percent more body fat at five to eight years old than those fed standard bottle milk.
The British researchers believe they took in more calories and experienced weight gain at a crucial stage in growth.
Mothers were once advised to give enriched milks to underweight babies if they were not breastfeeding. But they are now told not to ‘fatten up’ their babies unless they are premature.
Study leader Professor Atul Singhal, from the MRC Childhood Nutrition Research Centre at University College London, said: ‘This study supports the case in the general population for breastfeeding since it is harder to overfeed a breastfed baby.’
'Immediately, it raises the issue about the best way to feed those children small for gestational age, which should now be evaluated in the light of all current evidence.
'In public health terms, it supports the case in the general population for breastfeeding - since it is harder to overfeed a breastfed baby.
'And it will undoubtedly be of interest to formula milk companies wishing to improve their products' he added.
In the study, published online in the American Journal of Clinical Nutrition (must credit), body fat mass in five to eight-year-olds was 22 percent to 38 percent greater in those given nutrient-enriched milk.
The scientists said previous research suggested 20 percent of adult obesity may be caused by over-nutrition or other early excessive weight gain in infancy.
Researchers looked at two randomised, controlled, double blind studies - where neither they nor the mothers knew which kind of milk they were assigned - involving small newborn babies in hospitals in Cambridge, Nottingham, Leicester and Glasgow.
Mothers who had no plans to breastfeed were given either standard formula milk or a specially devised formula containing extra protein, energy-boosters, vitamins and minerals.
In the first study, which was conducted on 299 babies between 1993 and 1995, the formula was used for nine months.
The second study involving 246 infants between 2003 and 2005 was stopped early due to evidence of the link between early over-nutrition and later obesity found in the first study.
The UK has one of the lowest breastfeeding rates in Europe, with almost one in three new mothers never attempting to breastfeed compared with two percent in Sweden.
Previous research found babies on formula milk who were weaned onto solid foods too early - before the six month recommendation - were the fastest growing infants.
Scientists believe that the relationship between calorie intake and weight gain is far stronger in infancy than among older children.
By four months old, 75 percent of babies in Britain drink formula rather than breast milk.
Breastfeeding is known to be associated with slower weight gain - setting up healthier eating patterns - while it is thought infant formula increases the production of fat cells, fuelling weight gain throughout childhood.