When Is It Safe for Breastfeeding Moms to Begin Losing 'Baby Fat'?

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Feb. 16, 2000 (New York) -- Overweight new moms who need to get back in shape can safely start taking off the pounds with diet and exercise within weeks of giving birth, even if they are breastfeeding, a new study shows. However, one researcher feels that women should wait until their newborn is 4 to 6 months old.

"There are women who are afraid of dieting while breastfeeding because they are worried about harming the milk supply," lead author Cheryl A. Lovelady, PhD, tells WebMD. "This study shows that women who are overweight and breastfeeding can get back into shape slowly -- losing an average of about one pound a week -- without affecting the weight gain of the baby." Lovelady is with the department of nutrition and food service systems at the University of North Carolina at Greensboro.

The 40 women in the study were overweight, though not obese. All were at least 20% over their ideal weight, with the average woman being about 5 feet 4 inches tall and weighing 145 to 175 pounds. Four weeks after delivery, they were assigned either to a diet and exercise program or to a no-diet group that was instructed not to exercise vigorously more than once a week or restrict their diet. Women in the diet and exercise group were prescribed a diet containing 25% of energy from fat, 20% from protein, and 55% from carbohydrates. The goal was to cut approximately 500 calories per day while maintaining a nutritious diet. Lovelady says the emphasis was on reducing the amount of sugar and fat. "Basically, there was a decrease in potato chips, a decrease in soft drinks -- those types of foods -- with the goal being a gradual weight loss and a sensible diet," she says. Women in both groups were prescribed a daily multivitamin.

The exercise program consisted of four sessions per week of brisk walking, jogging, or aerobic dancing. The women were instructed to start slowly and work up to a maximum of 45 minutes per session at a level within their target heart rate range.

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At the end of the 10-week study, women in the diet and exercise group lost an average of over 10 pounds of their total body weight and almost nine pounds of fat mass compared with respective losses of almost 2 pounds and less than 1 pound in the non-exercise/dieting group. Body fat decreased by over 3% in the diet/exercisers, compared with almost no decrease in the other group. The average calorie decrease in the diet and exercise group was 544 calories per day compared with a decrease of 236 calories per day in the non-exercise/dieting group. The results are published in the Feb. 17 issue of The New England Journal of Medicine.

The average weight gain among infants was slightly less than 1 ounce per day for babies of mothers in the diet and exercise group, which Lovelady reports is similar to gains in the babies of the no-diet group. Average gains in length also were similar for all infants in the study.

However, in an accompanying editorial, a researcher from Baylor College of Medicine in Houston says although there were not major differences between the groups, the study was small and important differences can't always be seen except in larger trials. Nancy F. Butte, PhD, associate professor of pediatrics, says the study seems to confirm existing research showing that a moderate diet and exercise does not affect the quality of a mother's breast milk or her supply of milk, nor does it seem to affect the rate at which the infant grows, but she says more studies are needed to look specifically at breast milk changes in women who are dieting and exercising.

Another factor to consider is that giving birth and breastfeeding a baby bring changes to a woman's life and to her family that can be stressful and fatiguing. "I just think that four weeks is too early [to start trying to lose weight]," Butte tells WebMD. "Milk production is just getting established, and between all the stresses of adapting to a new child, it's a vulnerable time to start weight reduction." She advises that women who need to lose weight postpone a diet and exercise program until four to six months after giving birth, when breast milk is no longer the sole source of nutrition for the infant.

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Vital Information:

  • New moms who are breastfeeding and want to lose weight can start doing so within weeks after giving birth, according to new research.
  • A study shows that weight loss of one pound per week in the mother does not harm the milk supply or affect the growth of the baby.
  • One nutrition expert is cautious about the results of the study, and recommends women wait four to six months before starting a weight-loss program.
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