Pregnant ladies listen up; enjoy your cravings but don’t have seconds.

Pregnancy demands weight gain; there is no logical reason that growing a fetus inside you should not result in weight gain. Indeed, too little weight gain increases the risk of having a preterm birth and low-birth-weight offspring. On the flip-side, there are individuals who use pregnancy as an excuse to get fat. Perhaps I’m being a tad vain, but it’s true. Yet, excessive gestational weight gain (GWG) is associated with gestational diabetes, cesarean delivery, giving birth to fat infants, and increased risk of chronic diseases later in life.

Not surprisingly, a proper diet plays a central role in the pregnant mother-to-be’s health. Recently, Tielemans et al systematically reviewed the association between energy and macronutrient intakes and weight gain during pregnancy in both observational and intervention studies in low-, middle-, and high-income countries. In total, 56 studies with over 78,000 healthy women aged between 12-46 years were reviewed.

Somewhat unsurprisingly, higher energy intake was associated with greater GWG among high-quality studies, with inconsistent results being reported by low-quality studies.

Generally speaking, a higher protein intake was not associated with GWG. However, it was associated with lower GWG among normal-weight and overweight women, and when consumed in place of dietary carbohydrates and fats.

Most studies showed no association between GWG and total fat intake. Similarly, no association was found when looking at specific fatty acids and types of fat (saturated, mono-, and polyunsaturated).

Finally, most studies did not find an association between carbohydrate intake and GWG.

To summarize, pregnant ladies should watch their calories (within reason) and eat more protein, but otherwise enjoy their cravings.

Sugar for a baby’s belly

The irony of the above study is that pregnant women have to look after two bodies. Sure, gestational weight gain may depend more on calories than macronutrients, but what about the growth of the fetus? The transmission of obesity across generations is a concern, and fat moms greatly increase the risk of obesity in the offspring later in life. This raises the question, how do macronutrients play a role?

The answer, at least with regard to dietary carbohydrates, comes from Renault et al, who performed a secondary analysis of data from 222 obese women participating in a randomized controlled trial (RCT) and examined the association of maternal carbohydrate intake in early and late gestation with body composition in offspring at birth assessed by dual-energy X-ray absorptiometry (DXA). The RCT consisted of encouraging each woman to follow a 1200-1700 kcal/day Mediterranean diet while obtaining 11,000 steps per day for activity.

The offspring’s relative fat mass 24-hours after birth was not associated with the intake of digestible carbohydrates in early pregnancy (6-10 weeks) but was significantly associated with intake during late pregnancy (~32 weeks). Indeed, the offspring from a mother consuming 238 grams/day of carbohydrates (the average intake of the highest intake quartile) has a body fat percentage 2.8 points greater than a mother consuming 188 grams/day of carbohydrates (average intake of the lowest intake quartile). The glycemic index and load of the diet during late gestation also significantly predicted greater offspring fat mass.

Things are not as simple as eating fewer carbohydrates, however. Dividing up the women by their glucose tolerance shows that the significant association between carbohydrate intake and infant fat mass was not present in those with normal glucose tolerance, but increased with increasing intolerance (figure 1). Therefore, all mothers should consume lower glycemic load carbohydrates, but only those who are insulin resistant should consider limiting intake if their baby’s belly is a concern for them.

Active pregnancies benefit more than just the mom

Mothers-to-be can have some pretty wacky food cravings. The last thing I want is one of you reading this to start freaking out because your craving happens to be bagels and biscuits. For better or worse, it seems prudent to share the work of Wasinski et al, who recently used female mice to show that physical activity could be the fat-savior.

More specifically, female mice were sedentary or subjected to swim training (60 min daily at “moderate intensity”) throughout their pregnancy. The 3-month old offspring were then put on a high-fat diet to induce obesity. With no size or weight differences between the offspring when beginning the high-fat diet, those born to active mothers constantly ate less food and gained less bodyweight and fat mass than those born to the sedentary mothers. Notably, the reduced fat mass was seen in terms of body fat percentage as well, indicating that body composition was superior in the active-born mice regardless of bodyweight.

To accompany these physical advantages, the active-born mice also demonstrated greater insulin-stimulated glucose uptake and preserved insulin sensitivity in comparison to the sedentary-born mice. Interestingly, the proportion of carbohydrate and lipid oxidation (respiratory quotient) was similar between both groups of mice despite the active-born mice actually displaying reduced levels of spontaneous activity during the active period.

Finally, the expression of several genes was evaluated in fat tissue and skeletal muscle of the mice. In the muscle, adiponectin expression levels were significantly increased in the active-born mice only, with no differences in serum levels. The active-born mice also displayed 6-fold lower leptin levels than the sedentary-born mice. 

To summarize, staying moderately active during pregnancy has generational effects – so keep it up.