The Best Ways to Lose Weight After Pregnancy
Credit: Tyler Olson | Shutterstock.com

For some women, that joyful time when a warm and snuggly newborn has finally arrived can be mixed with emotions about the changes in their own bodies, and many of these women have questions about how they will lose the weight they put on over the past nine-plus months.

Studies show that many women appear to hold on to at least a couple of pounds postpartum, and a quarter of women retain 11 or more pounds (5 or more kilograms) a year after giving birth. After having a baby, a woman retains, on average, 2.5 to 5 lbs. (1 to 2 kg), said Kathleen Rasmussen, a professor of maternal and child nutrition at Cornell University. That may not seem like much, but if a woman goes on to have more children or gains more weight for other reasons, the pounds can add up, she said.

Holding on to pregnancy weight can lead to serious health consequences down the road, putting moms at risk for chronic conditions like heart disease and diabetes. And losing the pregnancy weight is important not just for new moms, but for babies, too. Going into a future pregnancy at a higher weight can put both the mom and the developing baby at risk for medical complications, such as gestational diabetes and hypertension.

To determine the best practices for women who want to shed the baby weight, Live Science dove deeply into the data, reviewing the best studies on postpartum weight loss and talking to key experts in the field. Ultimately, we found that losing weight after pregnancy boils down to three main points, starting before you even give birth:

For women worried about extra pregnancy pounds, the experts we spoke with agreed that it's certainly possible to return to your pre-pregnancy weight, and indeed, that should ultimately be your goal.

"Most women naturally lose much of the weight they gained in pregnancy without much effort," said Dr. Emily Oken, a professor of population medicine at Harvard Medical School in Boston. And although it's possible for women to lose all of their pregnancy weight without making major changes in their lives, the natural shift in women's lifestyles that happens after they give birth certainly introduces new challenges.

"It's not so much that [women] need to make major changes, but that they need to figure out how to fit in the healthy eating and activities they used to do," Oken told Live Science.

There's no getting around weight gain during pregnancy, of course. But it's important to understand how much weight you should gain, why your body is putting on pounds and how it plays a role in what happens after the baby arrives.

So, how much weight should a woman gain during pregnancy? It all depends on her body mass index (BMI) before she gets pregnant. [Calculate Your BMI]

According to the Institute of Medicine (IOM), women who are considered underweight should aim to gain 28 to 40 lbs. (12.7 to 18.1 kg); women with a normal BMI should aim to gain 25 to 35 lbs. (11.3 to 15.9 kg); women in the overweight category should aim to gain 15 to 25 lbs. (6.8 to 11.3 kg); and women in the obese category should aim to gain 11 to 20 lbs. (5.0 to 9.1 kg). (For women who are pregnant with twins, the recommended weight gain amounts are higher.)

And although a weight gain of 25 to 35 lbs. for someone with a normal BMI may sound like a lot — certainly, a newborn baby doesn't weigh that much — those extra pounds do serve a purpose. As illustrated in the infographic below, pregnancy pounds also come from the placenta, the growing uterus and growing breasts, and increased blood and fluid volume in the woman's body. And yes, added fat also weighs in.  

 

In addition, some studies suggest that gaining too much weight during pregnancy increases the likelihood of a cesarean-section delivery, according to the review. (While C-sections are generally considered safe, they do carry additional risks compared with vaginal births. For example, a C-section is a major surgical procedure, and having a C-section for a first birth can often lead to repeat C-sections in future deliveries.)

According to the IOM, one of the major reasons women should limit their weight gain during pregnancy is to reduce risks to the baby's health. Gaining too much weight during pregnancy increases the likelihood that the baby will have a high birth weight, which can put the baby at risk for obesity and metabolic syndrome during childhood, according to a 2015 review published in the journal Expert Review of Endocrinology & Metabolism. (Metabolic syndrome is a combination of medical issues that include high blood pressure, a large waist circumference and low levels of "good" cholesterol.)

Finally, gaining too much weight during pregnancy also may be associated with preeclampsia, the authors wrote. Preeclampsia is a serious complication that can develop during pregnancy when a woman has both high blood pressure and excess levels of protein in her urine. It can put both the mother and the baby at risk.

But the amount of weight a woman gains should not be spread equally over the three trimesters of pregnancy. The IOM advises women to gain between 1.1 and 4.4 lbs. (0.5 to 2 kg) during the first trimester. Then, during both the second and third trimesters, women are advised to gain 0.5 to 1 lb. (0.23 to 0.45 kg) per week, depending on their pre-pregnancy BMI. The IOM advises that, during these trimesters, underweight and normal-weight women gain 1 lb. per week, that overweight women gain 0.6 lbs. (0.27 kg) per week and that obese women gain 0.5 lbs. per week. [Having a Baby | Stages of Pregnancy]

 

But a key point for expecting women to keep in mind is that the amount of weight gained during pregnancy is associated with the amount of weight lost afterward — quite strongly, in fact.

"Weight gain during pregnancy is the single biggest predictor of postpartum weight retention," said Dr. Jacinda Nicklas, an assistant professor of internal medicine at the University of Colorado School of Medicine and the lead author of the 2015 review.

Oken agreed. "Gestational weight gain is the biggest contributor to postpartum weight retention," she told Live Science. "Women who gain within the recommended amount of weight during pregnancy have less weight to lose and are more likely to get back to their pre-pregnancy baseline."

But despite the risks associated with gaining too much weight during pregnancy, between 40 and 60 percent of women gain more than the guidelines recommend.

To keep weight gain within a healthy range, a woman should certainly not be "eating for two," experts say. A woman needs "close to zero extra calories in the first trimester," Rasmussen said. "The body makes a lot of immediate changes in response to pregnancy [in the first trimester], but these changes don't require a lot of calories," Rasmussen told Live Science. Even so, a lot of the "overgain" that women experience happens in that first trimester, she said.

Indeed, studies show that despite recommendations that women gain the least amount of weight during the first trimester, in reality, this is often the trimester when the largest amount of excessive weight gain (pounds gained above the recommended levels) occurs.

"Women don't need to gain more than a few pounds during the entire first trimester," Oken said. And doing so can have negative consequences. "It is becoming increasingly clear that excess weight gain, even very early in pregnancy, can predict later weight retention and [worse] heart health not only for the mom, but also for her baby," she said.

In a 2015 study published in The American Journal of Obstetrics & Gynecology, Oken found that weight gain in the first trimester was more strongly associated with weight retention at seven years postpartum than weight gain during the second or third trimesters. Too much weight gain in the first trimester was also linked to higher blood pressure after pregnancy than was weight gain in the second or third trimesters.

Why is it important to gain weight within the recommended guidelines during pregnancy?
Why is it important to gain weight within the recommended guidelines during pregnancy?
Credit: Viacheslav Lopatin Shutterstock.com

The excess weight gained above the recommended amount during the first trimester is primarily fat, as opposed to weight from the fetus, the placenta or extra fluid in the woman's body (because these weigh very little at this point in the pregnancy), according to the researchers. Unlike fluid and nonfat tissue, this fat gain is likely more difficult to lose after pregnancy, according to the researchers. [Body Changes During Pregnancy]

"It can be a challenge to not gain too rapidly" in the first trimester, Oken said. For example, women who experience the fatigue that is very common in the first trimester may overeat; other women may experience nausea that's helped by snacking, she said. 

And "in some cases, women might think that, 'Well, now that I'm pregnant, weight gain is expected, so I don't need to think so much about what I'm eating,'" Oken said. It's these women whom doctors especially want to educate about healthy weight gain during pregnancy, she added. However, "many women don't see their OBs [obstetricians] until the end of the first trimester, so we need to get the word out" in other ways, Oken said.

In order to keep weight gain within the guidelines, Oken recommends that women focus on eating nutrient-dense foods, including fruit, dairy products and nuts, and especially avoid "empty" calories or extra desserts. Also, pregnant women should try to avoid drinking their calories in sugar-sweetened beverages, and instead make sure to drink plenty of water, as the symptoms of thirst (such as fatigue and irritability) can sometimes be mistaken for hunger, she said. [How to Gain Weight During Pregnancy, the Healthy Way]

But women shouldn't beat themselves up if they deviate from a day of healthy eating.

Pregnancy can be stressful, and focusing so much on being perfect causes needless worrying during pregnancy, said Katherine Tallmadge, a registered dietitian and an op-ed contributor to Live Science. It's OK to indulge occasionally, but it's still important to be smart about such indulgences in order to avoid overgaining, Tallmadge told Live Science. So, when moms-to-be treat themselves, they should try for smaller amounts or stay on the healthier side of the "treat," she said. For example, if you're craving pizza, go for vegetable, she said. [How to Cope with Stress During Pregnancy]

Women who have gained too much shouldn't get discouraged, because everyone gains weight at different rates, Nicklas said. Women who do gain too much early on in pregnancy should try to slow their rate of weight gain as their pregnancy progresses, she said. Women who have a BMI greater than 35 before getting pregnant may not have to gain any weight during pregnancy, she said.

However, doctors don't recommend that women intentionally try to lose weight during pregnancy, Nicklas added.

After giving birth, the last thing that's likely on a new mom's mind is going on a diet. And according to Cheryl Lovelady, a professor of nutrition at the University of North Carolina at Greensboro, that's just fine.

"I tell moms, 'The first month, don't worry about your weight,'" Lovelady said.

Of course, a woman will immediately lose some of the pregnancy weight simply by giving birth — namely, the weight of the baby, the placenta and the amniotic fluid.

And over the next few weeks, a woman can also expect to lose the weight of the extra fluid in her body that built up during pregnancy. After the fluid is gone, what remains is the extra fat that the woman added during pregnancy.

Women should be able to lose their extra weight by six months after they give birth, Lovelady said.

"We recommend a weight loss of approximately 1 pound per week," Lovelady told Live Science. However, in reality, women will likely lose more weight at the beginning, and the weight loss will slow as they get closer to their goals, she said. By the end, it may be only 1 pound per month, but that weight loss will be a pound of fat, as opposed to fluid, she added. [2016 Best Bathroom Scales]

Not all of the experts agreed that all of the weight had to come off within six months. However, 12 months seems to be the upper limit for how long it should take for women to lose all of their pregnancy weight. That means women who started out at a normal BMI before pregnancy should aim to return to a normal BMI, and women who were overweight or obese before pregnancy should aim to return to their pre-pregnancy weight, and then continue losing weight, if possible, Nicklas said.

Nicklas added that the current research suggests that women who don't lose their weight within this time period are at greater risk of retaining the weight for the long term.

"I recommend that women talk to their doctor if they are having trouble losing weight" at this point, she said. "Many women may need the structure of an evidence-based diet or weight-loss program to lose their pregnancy weight."

It's also important for a woman to lose the weight before getting pregnant again, experts say.

"Ideally, a woman would be at a healthy weight by the time she enters her second pregnancy," said Paige van der Pligt, a researcher at the Center for Physical Activity and Nutrition Research at Deakin University in Australia. But because "the period of time between two pregnancies will be variable — and with approximately 50 percent of pregnancies being unplanned — timing for weight loss can be challenging," she said.

"But the research shows us that it is possible," she added.

With the exception of breast-feeding (discussed below), losing the baby weight is really no different from losing weight at any other point in life, according to the experts who spoke with Live Science. [The Best Way to Lose Weight Safely]

"Evidence shows us that both nutrition and physical activity play an important role in the weight-loss process for anyone attempting to lose weight," van der Pligt said. "For women following childbirth, this really isn't any different."

Indeed, in her 2013 review of studies on the topic, published in the journal Obesity Reviews, van der Pligt concluded that "overall, programs which target combined nutrition and physical activity strategies have been more effective than those which focus on just one of these." She noted that "programs which included individualized support are also important."

In the review, van der Pligt and her colleagues reviewed data from 11 studies that were focused on postpartum weight-loss interventions. They found that seven of the studies involved interventions that were effective in helping women lower their weight retention after pregnancy, and that, of these, six included both dietary and physical activity components, according to the review. The authors concluded, however, that "the optimal setting, delivery, intervention length and recruitment approach" for the most effective interventions remain unclear.

What works best for postpartum weight: diet, exercise, or both?
What works best for postpartum weight: diet, exercise, or both?
Credit: Odua Images Shutterstock.com

A 2013 meta-analysis published in the journal Cochrane Database of Systematic Reviews reached similar conclusions. Looking at data from 14 studies, the authors found that "diet combined with exercise or diet alone compared with usual care seemed to help with weight loss after giving birth" but that further research is needed.

Van der Pligt stressed that "diet and exercise" don't mean women need to go on an extreme diet or start training for a marathon. Several studies suggest that making small changes can be helpful for losing pregnancy pounds.

For example, in the Active Mothers Postpartum trial, which enrolled 450 overweight and obese postpartum women, cutting out junk food and being less sedentary were associated with postpartum weight loss. (Lovelady, who was an author on that study, noted that these results were specific to overweight and obese women. Women who start out at a normal weight and gain within the guidelines usually don't have an issue with postpartum weight retention, she said.)

Overall, a woman should be able to follow any healthy diet after pregnancy to lose weight, Lovelady said. Diets such as Weight Watchers, a Mediterranean diet or a vegetarian diet can all be good options, she said. [Mediterranean Diet: Foods, Benefits & Risks]

In addition, another, smaller study from Sweden — which included 68 overweight or obese women, all of whom were breast-feeding — found that dietary changes had the greatest impact on postpartum weight loss. Beginning at 10 to 14 weeks postpartum, the women were randomly divided into four groups for a 12-week intervention. One group was counseled about their diet, another on diet and exercise, and another on exercise alone. The fourth group received no advice and served as a control group, for comparison. The women in the diet-only group not only lost the most weight but were also the only group that continued to lose weight nine months later, according to the study.

Rasmussen, who was an author on the study, noted that the dietary changes the women made were not major. The intervention focused on cutting out junk food, eating more vegetables and eventually reducing the overall number of calories the women were consuming, she told Live Science. 

(One limitation of the study, however, was that the exercise component was not a huge change from the amount of physical activity the women were getting prior to starting the study, Rasmussen said. So, while they did adhere to the exercise requirements, it didn't represent a substantial increase in their energy expenditure, she said.)

"I can tell you, diet does work," Rasmussen said. She said, for weight loss, she recommends a diet that highlights nutrient-dense calories and avoids empty calories. [Diet and Weight Loss: The Best Ways to Eat]

And although diet appears to be the driving factor in losing the baby weight and exercise doesn't have a huge effect on weight loss, the experts agreed that it's still important for new moms to get back to moving as soon as possible.

Here's an easy way for new moms to get moving.
Here's an easy way for new moms to get moving.
Credit: Oleg Baliuk Shutterstock.com

Yes, gone are the days when women were confined to bed rest after giving birth — certainly, a woman should take care of herself and recover from giving birth, but it's important to get moving, Rasmussen said.

"Most women can start walking soon after giving birth, regardless of whether they give birth vaginally or have a C-section," Nicklas said. But women interested in doing more vigorous activity, such as lifting weights, should ask their OB when they can start, she added. 

All of the experts we spoke with agreed: Walking is a great way for new moms to get exercise. [2016 Best Pedometers]

Walking during the postpartum period has been shown to have excellent health benefits, van der Pligt said. Plus, it's convenient and cheap, and can be an important social activity for new moms, she added. [How to Start Exercising Again After Pregnancy]

In one of Lovelady's studies, for example, the women started their walking program at four weeks postpartum and gradually built up to walking for 45 minutes a day, five days a week, Lovelady said. The women in the study had been largely sedentary for the previous three months, however, she added. For most women, moderate exercise during pregnancy is considered safe and healthy.

It's also important to reduce inactivity. In a 2007 study published in the American Journal of Preventive Medicine, researchers looked at the effects of television viewing, walking and trans-fat consumption on postpartum weight retention. They found that women who watched less than 2 hours of television a day, walked for at least 30 minutes a day and limited their consumption of trans fat had a decreased likelihood of retaining at least 11 lbs. (5 kg) a year after giving birth.

Although researchers know that physical activity alone does not appear to cause weight loss, in combination with a healthy diet, regular exercise helps to maintain the weight loss that occurred, said Oken, who was the lead author of the study.

Although all of the experts interviewed agreed that diet and exercise strategies for postpartum weight loss don't really differ from the strategies one would employ for weight loss at any other time of life, after giving birth, women may have one unique advantage: breast-feeding. [Breast-feeding Basics: Tips for Nursing Mothers]

For example, in Rasmussen's 2008 study, published in The American Journal of Clinical Nutrition, the researchers concluded that "breast-feeding could also make a meaningful contribution, eliminating [postpartum weight retention by 6 months] in many women."

(Nicklas noted that, while full breasts may feel heavier, in reality, they wouldn't contribute much to a breast-feeding woman's weight.)

Certainly, there are several factors that play a role in whether breast-feeding has an effect on weight loss, including how intensively and how long a woman breast-feeds, Rasmussen said. But generally speaking, the more a woman breast-feeds, the greater an effect it will have on her weight loss, she said.

Simply put, breast-feeding burns calories — the body requires extra energy to make milk. (However, this might not be the entire explanation, Rasmussen said. Researchers haven't yet tested whether other factors also contribute to weight loss associated with breast-feeding, she said.)

Feed your baby, and lose weight too?
Feed your baby, and lose weight too?
Credit: didesign021 Shutterstock.com

Indeed, the calorie requirements for breast-feeding women are higher than those for women who are not breast-feeding. Women who exclusively breast-feed burn about 500 extra calories a day, compared with women who are not breast-feeding, Lovelady said. But generally, breast-feeding women are instructed to increase their caloric intake by only about 330 calories daily, she said. The resulting deficit contributes to weight loss.

In other words, the calorie recommendations for lactating women don't completely cover the amount needed to produce milk, Rasmussen said. Researchers assume that part of that caloric cost will be met by burning body fat, she said. So, for women who are reasonably active and gained a reasonable amount of weight during pregnancy, breast-feeding is really quite important, Rasmussen said. "But you can undo it all by overeating," she added.

Still, according to Rasmussen, between diet, exercise and breast-feeding, breast-feeding comes out on top as the most important factor in whether a woman will lose all of her pregnancy weight.

"You have to realize there are two players here: There's the mother, and the baby," Rasmussen said. "So the optimal [approach] for the mother and the baby together is, first for the mother to breast-feed. The "baby gets the best nutrition we have to offer, and the mother, if she doesn't overeat, will lose weight," she added. "If [a woman] wants to lose more weight than that, she can diet, she can exercise or she can do both," Rasmussen said.

However, researchers haven't reached a consensus on the effects of breast-feeding on weight loss.

"This has been looked at in many studies, and there's still not a clear answer" on the role that breast-feeding plays in postpartum weight loss, Nicklas said. If all of the studies are considered, however, there are probably slightly more showing that breast-feeding does help, she added.

But to reassure women who are not able to breast-feed, or choose not to, Nicklas noted that breast-feeding is not essential for weight loss.   

Van der Pligt agreed. Although many women do lose weight while breast-feeding, many studies have shown little or no influence of breast-feeding on a mother's weight change, she said.

"So we can't assume that just because a woman is breast-feeding, she will lose weight," van der Pligt said. It's more about promoting healthy, attainable lifestyle behaviors that will have health benefits for women and assist her in achieving a healthy weight following childbirth, she said.

This article is part of a Live Science Special Report on the Science of Weight Loss. It will be updated whenever significant new research warrants. Note that any significant change in diet should be undertaken only after consultation with a physician.

Follow Sara G. Miller on Twitter @SaraGMiller. Follow Live Science @livescience, Facebook & Google+. Originally published on Live Science.