Pregnancy weight gain won’t make your baby fat

by Ellyn Satter, Registered Dietitian and Family Therapist

Currently, weight hysteria is being focused on pregnancy. However, as I pointed out in Big babies do not become big adults, data correlating high birth weight with child and adult “overweight” is a numbers game that pictures as abnormal what for many children is normal growth. Instead of interfering with maternal nutrition during pregnancy, it is far better to encourage pregnant women to eat as much as they are hungry for and gain weight in a way that is right for them.

A numbers game

The “fetal overnutrition hypothesis”¹ contends that the seeds of later overweight are planted in the fetus by parents’ high BMI, the mother’s “excessive” obstetrical weight gain, and/or delivering a large baby. However, five percent of children normally plot at the 95th percentile or above. Those relatively large and normally growing infants continue to be relatively large at age 7 years and as adults. Relatively large mothers, and to a lesser extent, relatively large fathers, tend to have relatively large babies. The problem arises when, in today’s weight-preoccupied world, that normal largeness is labeled overweight or obesity and alarmed parents are warned not to let their infant eat “too much” or downright pressured to restrict their infant’s food intake. Not only does such doubt and restriction create misery for both parents and child, it creates the very problem it is intended to avoid. Parents who don’t trust their child to eat and grow well restrict either directly or indirectly. Children whose food intake is restricted become food-preoccupied, eat a lot when they can, and gain too much weight.

The real problem is low birth weight

It is ironic that the same weight hysteria is not focused on low birth weight, which is far more clearly problematic. Low birth weight correlates with increased adult hypertension,^2,3 cardiovascular disease, and type 2 diabetes.² Epidemiological studies worldwide demonstrate a relationship between poor fetal growth and increased susceptibility to insulin resistance, obesity, and type 2 diabetes. A study of 150,000 pregnancies show that a one kg (2.2 lb) increase in birth weight correlates with a 10-20% lower risk of subsequent heart disease.⁴  There may be a U-shaped relationship between birth weight and disease. Low birth weight (less than 2,500 g, or 5.5 lb) or high birth weight (more than 4,000 g, or 8.8 lb), as compared with birth weight between 2,500 and 4,000 g, was associated with slightly increased risk of type 2 diabetes.⁵

Dieting during pregnancy is the culprit

Food restriction and striving for stated weight-gain outcomes during pregnancy distorts eating attitudes and behaviors and increases the risk for both mother and baby.

 

Food restriction can create havoc with metabolism during pregnancy and harm the baby. Extensive metabolic research suggests that the culprit linking food restriction and/or low weight gain during pregnancy and subsequent disease is fetal exposure to high levels of glucorticoid. This is a hormone produced by the mother to stimulate gluconeogenesis,⁶ the conversion of protein (and other arcane substances), to glucose, or energy. Energy is the primary requirement of the fetus, and if the mother doesn’t consume enough energy, her levels of glucocorticoid go up and she burns protein, including her own body tissue, to get it. 

In pregnancy, as always, do no harm

These low correlations and contradictory results of the “fetal overnutrition hypothesis” are nowhere near convincing enough to support interference with maternal nutrition during pregnancy. In fact, raising the alarms creates harm. It carries the potential for increasing women’s concerns about child overweight beginning in pregnancy and exacerbates the risk of distorting feeding dynamics throughout the child’s growing-up years. Food restriction and striving for stated weight-gain outcomes during pregnancy distorts eating attitudes and behaviors and increases the risk for both for both mother and baby. Mothers who are concerned about a child’s weight tend to feed in a restrained fashion-they try to get the child to eat less food and less-appealing food than they wish.⁷ The evidence shows that restrained feeding with respect to both amounts and types of food clearly correlates with increased child overweight.