For decades doctors have agreed that breastfeeding has significant advantages for both mom and baby. Mother's milk helps build baby's budding immune system, establishes emotional bonding and even triggers the release of oxytocin, the so-called "love hormone" that is associated with both hugging and orgasm.
But what about weight loss for the mother? At least one study says this is a myth. But those who work with nursing mothers say the issue is more complex and argue that in the long run, breastfeeding does contribute to overall fitness.
Just this week sexy actress and new mother Salma Hayek told Oprah in animated tones, "It's a lie! It's not true! I'm going to say something. Except for a couple of exceptions, the only reason people lose weight like that when they're breastfeeding. It's that they're not eating and they're breastfeeding. And that's not good for the baby."
Her reaction is typical of the strong opinions many mothers have about breastfeeding and weight gain.
Like Amanda Socci, who says she tipped in at 210 pounds when she gave birth to her daughter in 2006. One year after delivery, Socci made little progress in getting back to shape.
But now - two years after delivery - the 36-year-old, first-time mother, who is still nursing her daughter Margarita, has lost 40 pounds. She attributes the eventual weight loss to running around after a toddler, not to breastfeeding.
"People say nursing helps you lose weight," said Socci, who works as a volunteer in her hometown of Alexandria, Va. "It doesn't help. Every two hours I was sitting and nursing. I couldn't walk or run. I was eating more. But when my daughter learned how to walk, I started running. I couldn't keep up with her."
The truth probably lies somewhere in the middle. Breastfeeding does have a metabolic effect that encourages the body to return to its natural shape. But nursing alone, especially if mother leads a sedentary life and hits the freezer for ice cream — just won't burn off the pounds.
Most studies show that mothers who "eat to hunger" show a steady, gradual weight loss while nursing, according to Kathleen Huggins, author of the classic "Nursing Mother's Companion," which has sold more than one million copies.
"There may be a wide variation in the loss but most nursing mothers lose most of their weight during the first three to six months post partum," Huggins told ABCNews.com. "A few studies may show little difference in weight loss and this may be because breastfeeding is not clearly defined. Some mothers may only be partially breastfeeding."
Hayek, 41, who won an Academy Award nomination for best actress for the 2002 film, "Frida," said she has struggled with her weight since her daughter Valentina Paloma was born last September. She was also treated for gestational diabetes — a common, but temporary form of the disease that increases the size of the fetus and leads to weight gain, among other medical hazards.
Socci, too, experienced gestational diabetes and was placed on a strict diet during her pregnancy, avoiding sugars and salt. But after delivery, she was able to return to a normal diet and found breastfeeding increased her appetite.
Hayek's story elicited numerous reactions online. Kendra, a mother of four, commented on Huffington Post that exercise and breastfeeding, "will shrink your stomach up. I'm thinner now than I was in high school.