This is the first of a two-part series on fitness and nutrition for new mothers. The next column focuses on nutrition and weight loss.

Q. Can you really get back your old body, or even a better one? If so, how long should it take?

A. Postnatal exercise experts Lisa Druxman and Dr. Jennifer Wider say yes, but it takes discipline and time (three to 12 months). New moms should make exercise a priority and perhaps buy or rent fitness DVDs, take long walks or do yoga while baby sleeps.

A review by Cochrane Library suggests women who return to their pre-pregnancy weight within six months have a lower risk of being overweight 10 years later.

Q. What are the benefits of post-natal exercise?

A. Wider says it can speed a woman's recovery time after delivery and studies suggest it can increase energy and lower a woman's chances of postpartum depression.

Q. How long should I wait after delivery before working out?

A. Most physicians recommend waiting six weeks to resume a traditional exercise program, but Druxman suggests immediately starting pelvic floor rehab by doing Kegel exercises (squeezing the muscles that stop the flow of urine for three to five seconds 15 times at least three times a day) and adding gentle pelvic tilts and small abdominal crunches in the first couple weeks, short five- to 15-minute walks after two to four weeks and maintaining the routine until after six weeks.

However, she said to avoid strenuous exercise; stop if the exercise causes pain, dizziness or an increase in bleeding; and avoid wide squats and big lateral movements.

Q. When can I start exercising after a cesarean section?

A. The body needs time to heal after this major surgery, but many women are ready to resume intermittent walking or other gentle exercise after two weeks, Druxman says, and Wider says at six weeks women can start isometric exercises — resistance training that involves contracting muscles without moving the joints.

Q. What are the best exercises for getting back in shape?

A. Walking. And even better, walking with a stroller. A study by the American Council on Exercise showed that using a stroller burned approximately 18 to 20 percent more energy at 3 mph and 3.5 mph than walking without a stroller (on average 6.2 and 7.4 calories per minute respectively).

If you walk with baby in a sling, keep your shoulders down and back, your neck long and relaxed and regularly contract your shoulder blades, bringing them together as if you were squeezing a pencil.

A rowing machine, or using resistance tubes or bands to row or work your biceps, can help build up strength for carrying your baby.

Charles Stuart Platkin is a nutrition and public-health advocate, and author of "Breaking the FAT Pattern" (Plume, 2006). Sign up for the free Diet Detective newsletter at www.dietdetective.com.