Through menarche pregnancy the post-partum period and menopause women’s bodies undergo several hormonal transitions which as many of your female patients can likely attest wreak havoc with maintaining a healthy weight. Weight gain during pregnancy can be especially difficult to navigate. Obviously women should gain an appropriate amount of weight during pregnancy but some people can take the notion of “eating for two” a little too far and end up with excess body fat that is extremely difficult to lose even after a long period of breastfeeding which often results in weight loss naturally. Compound this with the growing epidemic of gestational diabetes and it becomes especially important for women to make wise dietary choices during pregnancy.

British researchers studying fruit flies have uncovered a mechanism by which the fertilization of eggs induces changes to the maternal intestine enlarging it and enabling it to extract more energy from food and store more fat. We can’t automatically extrapolate research on fruit flies to apply to humans but this fly hormone called “juvenile hormone” acts similarly to thyroid hormone which plays a role in regulating human metabolism. Other hormones related to fertility and pregnancy may have similar effects in women. 

It is generally assumed that a woman’s appetite increases during pregnancy in order to meet the increasing energy demands of the growing fetus. But this research indicates that at least in fruit flies these adaptive changes to the intestine and the resulting increased extraction of food energy occur very early on after fertilization. According to the researchers “Previous studies have shown that eating for two during early pregnancy is unnecessary. Our research suggests that this is because the digestive system is already anticipating the demands that the growing baby will place upon our body.” This means rather than requiring more total food a pregnant woman’s body may be physiologically adapted—at least temporarily—to harvest more calories from the food she’s already eating.

This is not to say that pregnant women don’t require additional nutrients and slightly more calories than they’re accustomed to eating when not pregnant. But “eating for two” may be a stretch particularly when the second of those two weighs approximately 6-9 pounds and isn’t exactly doing triathlons inside the womb.

Pregnant women know they should be mindful of what they eat because their own diet not only provides direct nourishment to their growing baby but also influences and enables the proper physical development of the baby’s body. But there’s another equally important reason for women to choose healthful whole unprocessed foods in appropriate amounts for their individual constitution and physical activity levels: the nutritional environment in utero can induce epigenetic changes in the offspring—some of which might be irreversible—and which may lead to obesity diabetes cardiovascular issues and other health complications either during adolescence or even throughout the lifespan. A child’s “metabolic phenotype” can be conditioned by its gestational environment which may make it easier or more difficult to maintain good health and a healthy body weight regardless of what he or she eats later on in life.

There’s a fine line to walk regarding maternal caloric intake and the makeup of those calories. Too much energy is detrimental to both mother and baby but too little energy is also problematic. Malnourishment during gestation may condition babies to have a “thrifty” metabolism—one that is programmed to extract more energy from food or to have an exaggerated response from eating excess carbohydrates and fats. In an environment of food scarcity this is a protective phenotype but upon exposure to the year-round abundance of inexpensive calorie-dense nutritionally empty foods later in life these people are more likely to develop metabolic syndrome diabetes and other health complications.

Beyond diet it’s important for pregnant women to manage their stress levels. Increased cortisol levels during gestation can have long-term effects on their offspring as well. High maternal cortisol may result in cardio-metabolic disorders cognitive problems and mood disturbances in offspring.