By SUZANNE BOHAN
Chron.com

As if new mothers don’t have enough challenges.
Now they need to get adequate sleep if they want to keep postpartum weight off, according to research released Monday from Kaiser Permanente and Harvard Medical School.


New moms who reported getting less than five hours or less of slumber per day when their infants were 6 months old were three times more likely to carry an extra 11 pounds by the baby’s first birthday, according to a study of 940 women published in this month’s issue of the American Journal of Epidemiology.

The findings, however, aren’t intended to throw up another daunting goal for new mothers, said Erica Gunderson, Ph.D., a Kaiser researcher and lead author of the study.
Rather, women frustrated with their inability to shed pounds packed on during pregnancy now have another strategy besides joining a gym or cutting calories to lose that unwanted excess.
“We should help women get enough sleep and not just focus on diet and exercise,” said Gunderson.
Every parent remembers the ensuing months of sleep deprivation following a baby’s birth. But the burden falls especially hard on women. One 2004 study found that women lost 42 minutes of sleep a night, compared with 16 minutes for men, in the months after a newborn arrived home.

The Kaiser/Harvard study is the first to analyze the role of sleep deficiency on weight gain in mothers, and its findings dovetail with years of research directly connecting too little sleep with excess girth in all adults.

A 2006 study of 68,000 women found that during a 16-year period, those sleeping five hours or less a night were one-third more likely to gain 33 pounds or more, compared with women snoozing at least seven hours nightly.

What’s less understood is why a dearth of sleep leads to weight gain, although the Kaiser/Harvard study noted that a shortage of sleep, defined as less than seven hours daily, triggered increased levels of hormones called leptin and ghrelin, as well as the stress hormone cortisol, all of which stimulate appetite.

The research on the 68,000 women, however, found that women who slept less actually ate less as well, leading those researchers to conclude that exhaustion dissuaded those women from exercising, and the sleep loss may also have altered their metabolism.

“The exact mechanism behind the weight gain,” Gunderson noted, “needs further explanation.”

The Kaiser/Harvard researchers studied 940 women in the Boston area. The scientists took into account factors like diet, exercise, weight gain during pregnancy, as well as breast-feeding habits, before isolating the effects of sleep on weight, Gunderson said.

“We still found a strong association with sleep,” she said. “It suggests in the postpartum period there are some behaviors we may be able to modify.”

Gunderson added that only 13 percent of the women had retained at least 11 pounds one year after their baby’s birth, compared with their pre-pregnancy weight. However, four-fifths of the women participating in the study were white, most had college degrees, and 90 percent lived in households with annual incomes higher than $40,000.

Gunderson said studies more inclusive of a variety of races and income levels found that 15 to 20 percent of women gained significant amounts of weight one year following childbirth.

The study didn’t address, Gunderson added, whether sleep needs to be continuous, to ensure enough rest, or simply add up to at least seven hours of slumber daily.

The study also left unanswered how mothers can get adequate sleep, given the demands of a newborn. While infants usually sleep 14 to 18 hours a day, they rarely do so for longer than three hours consecutively, according to the National Sleep Foundation. In addition, some babies prefer to sleep more during the day.

That’s a subject for subsequent research, Gunderson noted. “We need to find out the reasons some women are only getting five or fewer hours (of sleep) per day,” she said.

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