Most of us who have had children can relate to the common pregnancy self-talk that, as we enter the drive-thru, says, “I’m already going to gain a ton of weight. What’s another few pounds?”But research has demonstrated that even a few extra pounds above the recommended weight gain amount increases a woman’s chances of retaining excess weight after pregnancy and becoming obese in the long-term. In one large study, 14.2 percent of previously normal-weight women became overweight by one year postpartum. And among normal-weight woman, 40 percent of them put on excess pounds during their pregnancies.MORE: Why Are People Obsessed With Pregnant Celebrities?Given that this added weight increases the risk of long-term obesity in both the mother and the infant, preventing the excessive weight gain in the first place is central.A new study highlights an exercise and nutrition program that succeeded in preventing a significant number of women from gaining excessive weight during their pregnancies and also from retaining extra weight afterwards. Women were divided into three groups: a moderate-intensity exercise group who received nutritional counseling, a low-intensity exercise group who also received the same nutritional counseling, and a control group who received no intervention.The exercise program was simple: Walk. The first week began with 25 minutes of walking three to four times a week. The women gradually increased their walk time to 40 minutes.MORE: 7 Easy Ways to Reach 10,000 StepsThe nutrition program was equally simple, with suggestions for calorie intake that would support the recommended progressive weight gain (about 2000 kcal per day). The women were instructed to eat three meals and three to four snacks per day, with 40-55 percent of the calories coming from complex and low-glycemic index carbohydrates, 30 percent of the calories stemming from healthy fats, and 20-30 percent coming from protein.The results, for the most part, were what you would expect. A lower percentage of women in the exercise groups gained excessive weight when compared to the controls, and they also retained less weight at two months postpartum.But the surprise comes between the two exercise groups.No significant difference was found between gestational weight gain in the low-intensity group versus the moderate-intensity group. You would expect more dramatic results from the higher-intensity group, but this was not the case. Thirty-one percent of the moderate-intensity group gained above the recommended weight, while 35 percent of the low-intensity group did…not a significant difference. By contrast, 53 percent of the women in the control group gained excessive weight.MORE: Handling Body Image Issues During PregnancyA few possibilities surface to explain the similar weight gains in the exercise groups of different intensities. One explanation is that the higher-intensity group ended up burning fewer calories from non-exercise activities during the rest of the day. Maybe they were just more worn out from the exercise, and it manifested itself in decreased activity later. Another possibility, as proposed by the researchers, is that, even though the two exercise groups reported similar caloric intake, the higher-intensity group may have actually consumed more calories to make up for the calories burned in the exercise.Whatever the causes, the message remains the same. Low-intensity exercise appears to be as beneficial as moderate-intensity exercise for decreasing the risk of excessive weight gain in pregnancy.Another interesting side-observation of the study was that almost half of the women who ended up gaining excessive weight, had already gained much of it before the start of the intervention (16-20 weeks gestation). This finding suggests that women who have not been exercising prior to conception should begin to exercise earlier than they did in this study. If you are newly pregnant or are hoping to be soon, aim for starting an exercise program at the beginning of the second trimester, about 13 weeks gestation, when the risk of miscarriage is low.MORE: Skincare You Can’t Use During PregnancyIf you have been exercising before conception and have no complications that make exercise unsafe during pregnancy, you can continue your program as comfort allows, taking extra care to avoid exercise in hot and humid conditions. And remember, a modest stroll seems to be about as effective for healthy weight gain as a brisk power-walk.