Q. Does it matter how much weight I gain when I am pregnant?

A. Tempting as it sounds, eating for two does not mean eating twice as much. In fact, most women only need an extra 300 to 400 calories daily to support a healthy pregnancy. That's the amount of calories in just one keiki-sized fast-food cheeseburger!

While hāpai, gaining either too much or too little weight can alter your baby's internal programming in ways that may affect its health for years to come. Babies whose mothers gain too much or too little weight during pregnancy are at increased risk of developing diabetes and heart disease as adults.

Gaining too little weight can deprive the fetus of nutrients during critical phases of development. Also, when too few calories are available to the fetus, "thrifty genes" may be expressed, encouraging the body to store fat and hoard every calorie. People with thrifty genes gain weight easily and have difficulty losing weight. Lastly, too little weight gain often results in a baby being born underweight. These babies are prone to infections, which lead to inflammation often associated with heart disease and diabetes.

In the case of gaining too much weight, the baby may end up being too large at birth. As children, they have excess body fat, putting them at risk for obesity-related diseases in adulthood. Changes in programming of processes that control appetite, metabolism and gene expression may be responsible. In addition to diabetes and heart disease, baby girls with high birth weights are at increased risk of developing premenopausal breast cancer as adults.

The Institute of Medicine provides guidelines for pregnancy weight gain based on weight before conception. IOM recommends normal-weight women gain 25 to 35 pounds, underweight women gain 28 to 40 pounds, overweight women gain 15 to 25 pounds, and obese women gain 11 to 20 pounds. Women carrying twins need to gain more weight than recommended here.

Health experts generally agree with these recommendations; however, when it comes to obese women, there is some controversy. Several studies have shown that obese pregnant women who followed well-balanced diets and gained little or no weight had healthy babies. Some doctors believe that as long as the fetus is growing, this should be acceptable.

If you are pregnant and need help determining the right amount and types of foods to eat, seeking the guidance of a registered dietitian would be beneficial.

Amy Tousman is a registered dietitian and certified diabetes educator with Nutrition Unlimited in Kailua. Send your questions to: Prescriptions, Island Life, The Advertiser, 605 Kapi'olani Blvd., Honolulu, HI 96802; islandlife@honoluluadvertiser.com; or fax 535-8170. This column is not intended to provide medical advice.