Giving regular, short breastfeeds is more beneficial than the "baby-led" method, a British study suggests.
Allowing a baby to choose when it feeds, and for how long, is often recommended to new mothers.
A study of 63 mothers in Bradford found regular feeds of up to 10 minutes on each breast led to increased weight gain and a higher breastfeeding rate.
However, midwives said the method suggested in Archives of Disease in Childhood would not apply to everyone.
The World Health Organization recommends that babies are exclusively breastfed until they are six months old, but only around one in four UK mothers follows that advice.
The researchers, led by Dr Anne Walshaw, a GP, had noticed poor weight gain among breastfed babies after baby-led feeding became more common.
They set up a study at one Bradford GP practice of 63 mothers who exclusively breastfed their babies.
Half were told to feed as and when the baby wanted to, and to offer the second breast only if the baby showed signs of still being hungry.
The rest were advised to feed their babies for a maximum of 10 minutes on each breast around every three hours during the day and, if necessary, at night.
The women in the second group were also told to leave at least two hours between feeds.
Fewer than half of the babies in the baby-led group were still breastfeeding after 12 weeks, compared with over three-quarters of those whose mothers followed the traditional method.
In addition, baby-led feeding and feeding for more than 10 minutes from the first breast, were both linked with poorer weight-gain in the first six to eight weeks of life.
The researchers say baby-led feeding disrupts the body's system for producing breast-milk.
A dose of a hormone called oxytocin is needed to trigger the "let-down reflex", which causes milk to travel from cells in the breast via ducts to the nipple.
But if babies stay on the breast for too long, this oxytocin production is disrupted.
The researchers also said if babies are not put onto the second breast, which will also be full of milk, at each feed, a protein is produced which stops further milk being made, disrupting the feeding process for hours and perhaps days.
'Baby will know'
Writing in Archives of Disease in Childhood, the team led by Dr Walshaw, said: "Babies feeding from both breasts at each feed receive more milk than babies feeding from one breast, and those feeding for shorter average lengths experience increased weight gain and other positive outcomes."
But Hilary English, a breastfeeding adviser for the National Childbirth Trust, said it was possible that limiting feeds to 10 minutes per side would reduce milk production and babies would be under-nourished.
"In general, baby-led feeding is best. A baby will know how much he or she needs."
And Janet Fyla, professional policy adviser for the Royal College of Midwives, said mothers should be guided by if their baby is growing well.
"You cannot generalise. A baby who is getting enough milk will feed for long enough and then come off," she said.