Dieting and Infant Growth

Study shows dieting among overweight women who breastfeed does not affect infant growth

A recent study of overweight women who exclusively breastfeed showed that dieting and weight loss does not affect the growth of their infants.

Researchers at the University of North Carolina at Greensboro randomly assigned 40 breastfeeding women who were overweight (according to a body-mass index) at four weeks postpartum to two groups. One group dieted by cutting 500 calories a day and exercised for 45 minutes a day for four days a week. The second group did not change their usual daily calorie intake and did not exercise more than once a week.

For 10 weeks the researchers monitored the mothers and their babies. The mothers were measured by weight and fat mass and their babies were measured by length and weight.

The women who were dieting and exercising lost an average of one pound per week, significantly more than women in the comparison group. Meanwhile, their babies grew about an average of three inches and four pounds - measurements not significantly different from the infants of mothers who did not diet or exercise.

The researchers concluded that weight loss of about one pound a week between 4 and 14 weeks postpartum in overweight women who are exclusively breastfeeding does not affect the growth of their infants.

Some nutrition experts are reassured by these findings, but claim that they should be interpreted cautiously. "These babies were studied at a very rapid period of growth, especially for the breastfed baby, and 10 weeks is a very short period of time," said Dr. Judith Roepke, Dean of the School of Continuing Education and Public Service and Professor of Family and Consumer Sciences at Ball State University. "We cannot tell from the study what the long-term effects of this regimen would be on the mother or the baby."

Dr. Roepke believes that the researchers adopted a very responsible approach to weight loss following pregnancy, however. "The fact that they incorporated exercise into the weight loss program is very important, because exercise protected the lean body mass of these women. If you want to lose weight, this is the right way to do it," she said.

Still, Dr. Roepke would recommend that new mothers who need to lose weight first try exercise alone, without dieting, and that they monitor their weight loss carefully. "Women can lose too much weight too soon," she said. "Those who reach their lower body-mass index while breastfeeding should increase their caloric intake to compensate-especially if they exercise."

Any diet or exercise program that a woman adopts following delivery should be individualized and discussed with her health care provider.

The results of the study were printed in the February 17, 2000 edition of the New England Journal of Medicine.