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January 2012

Does Childhood Obesity Start at Conception?

 

baby

By Natalie Digate Muth, M.D., M.P.H., R.D.

It is no secret that the United States faces an epidemic of childhood obesity. Obesity prevalence among children has increased from 5 percent in the 1960s to about 17 percent currently (Ogden et al., 2006). Few would argue that the changes in the way we live—from how we get to work and school to what we eat for snacks and meals—are responsible for the rapid and alarming widening of our waistlines from infancy to old age. But it turns out that, for many kids, the risk of obesity starts long before their first fast-food outing, bowl of ice cream, or entire afternoon spent watching TV or playing video games.

A growing body of research points to the role of the prenatal environment on later health outcomes for children, especially when it comes to the propensity to gain weight. A retrospective study of 10,000 babies found that the risk of overweight by age seven was 48 percent higher for babies whose moms had excessive pregnancy weight gain, even after accounting for numerous potential confounders (Wrotniak et al., 2008). Other studies found similar results for preschoolers and adolescents (Oken et al., 2008; Oken et al., 2007). Results from a study presented this past summer at the Endocrine Society meeting found that women who gained excessive weight during pregnancy had newborns with more fat mass than newborns whose moms gained the appropriate amount of weight—17.5 ounces of fat compared with 13.9 ounces. About 70 percent of women exceeded weight-gain recommendations (Josefson, 2011).

Institute of Medicine Guidelines for Weight Gain
Pre-pregnancy BMI Total Weight Gain (lb)

Weight Gain 2nd/3rd
Trimesters (lb/week)

Underweight (<18.5 kg/m2) 28–40 1.0−1.3
Normal weight (18.5−24.9 kg/m2) 25−35 0.8−1.0
Overweight (25.0−29.9 kg/m2) 15−25 0.5−0.7
Obese (> 30kg/m2) 11−20 0.4−0.6
Source: Rasmussen K. and Yaktine, A. (2009). Weight Gain During Pregnancy: Reexamining the Guidelines. Washington, D.C.: Institute of Medicine.

 

It appears that there is something about moms gaining more than the Institute of Medicine recommendations that may predispose their kids to pack on the pounds. Researchers suggest several potential explanations for the relationship between excess pregnancy weight gain and childhood obesity, but none are certain. For instance, it may just be that moms who gain too much share the same obesity-promoting genetic make-up and dietary and activity preferences as their kids. While certainly this plays some role, the relationship between too much pregnancy weight gain and childhood obesity holds even for moms who started pregnancy at a normal weight. It probably has a lot to do with blood sugar, which tends to be elevated in women who gain too much weight, whether or not they develop gestational diabetes. Glucose passes through the placenta, but insulin does not. When the fetus experiences the elevated blood sugar, his or her pancreas must secrete more insulin to normalize blood sugar levels. Insulin itself is a growth factor causing a fetus to be larger. It also may initiate a hormonal cascade that leads to increased appetite and weight gain in childhood, adolescence and adulthood.

While excess weight gain during pregnancy is associated with harmful outcomes for infants regardless of mom’s pre-partum weight (in fact, the effects are most pronounced for underweight moms who gain too much weight), overweight women are more likely to give birth to underweight or overweight babies; both are scenarios that increase an infant’s risk of obesity later in life.

Taking Action
Both an expecting mom and her developing baby can benefit enormously from lifestyle changes a mom makes during pregnancy. Here are some important tips to offer your pregnant clients to help them achieve the healthiest possible outcome.

Curb Excessive Weight Gain
Perhaps the most important action an expecting mom can take is to optimize her nutrition and physical activity during pregnancy to avoid excessive weight gain. A pregnant woman needs about an extra 300 calories to support a developing baby—a little less in the first trimester and more in the third. An expecting mom should let hunger be her guide in determining how much to eat, but she should also keep an eye on the scale to prevent excessive weight gain. If she is gaining too little or too much, she should pay careful attention to her nutrition and physical-activity habits.

The research to date is insufficient to guide obstetricians and expecting women with proven strategies to prevent excessive weight gain (Gardner et al., 2011). The best advice you can give your clients may simply be to go back to the basic principles for weight management for the general population: balance calories in with calories out. And that comes from a well-thought-out nutrition and activity plan.

Food Choices
For optimal maternal health and growth of the baby, the Federal Government recommends an individualized Daily Food Plan for Moms (check out choosemyplate.gov). The following general guidelines should set the stage for a healthy pregnancy and appropriate weight gain.

  • Eat five small meals per day including breakfast, lunch, an afternoon snack, dinner and an evening snack. 
  • Focus on fruits, vegetables, whole grains and high-calcium foods to meet micronutrient (vitamin and mineral) needs. Most obstetricians also recommend a prenatal vitamin for “insurance.”
  • Meet increased protein needs through a varied diet high in nutrient-dense foods and lean proteins.
  • Eat low-mercury fatty fish twice per week. Some research suggests that fish oils (omega-3s) may enhance pregnancy duration and improve the baby’s later cognitive, visual and cardiovascular development.
  • Leave a little room to satisfy cravings, but try to limit “empty” calories (food without much nutritional value).

In addition to the standard guidelines above, some new research suggests that an expectant mom can also eat to shape her growing baby’s food preferences. That is, she may be able to stamp out picky eating and start her baby loving fruits and vegetables in utero. Researchers at Monell Chemical Senses Center in Philadelphia have been studying how the food an expecting mother eats flavors the amniotic fluid surrounding a fetus and subsequently an infant’s acceptance of various foods. In one study, researchers divided women into three groups: those who drank carrot juice every day during pregnancy, those who drank carrot juice everyday while breastfeeding, and those who avoided carrots completely. Then, when the babies began solid foods, the researchers videotaped their responses when fed rice cereal made with either water or carrot juice. The babies that had been exposed to carrot flavors in amniotic fluid or in breast milk ate more of the carrot-flavored cereal and they made fewer negative faces while eating it (Cuda-Kroen, 2011). This may be one reason why babies from cultures in which a pregnant woman eats spicy, bitter and pungent foods have kids who lovingly accept those foods. It may also be one way to get kids turned on to fruits and vegetables and help to avoid overweight and obesity.

Physical Activity
The American College of Obstetricians and Gynecologists (ACOG) recommend that otherwise healthy pregnant women engage in at least 30 minutes of moderate-intensity exercise on most if not all days of the week (ACOG, 2002). To expound on these guidelines, ACOG published clarification by the researchers Zavorksy and Longo in the May and June 2011 issues of Sports Medicine (Zavorsky and Longo, 2011a) and Obstetrics and Gynecology (Zavorsky and Longo, 2011b). The goal is to exercise at an intensity of at least 60 percent of the heart-rate reserve while gradually increasing physical-activity energy expenditure to reduce the risk of gestational diabetes. The more vigorous the exercise, the less total exercise time is required. The researchers note that light muscle strengthening performed during the second and third trimesters of pregnancy has minimal effect on newborn body size and overall health.

A mom who is physically active during her pregnancy not only improves her own health and well-being, but may also improve the heart health of her baby. In one study, babies of mothers who were physically active had lower heart rates and greater heart-rate variability at 36 weeks gestation (May et al., 2010). Of course, exercise also provides the additional benefits of helping to stave off both excess weight gain and gestational diabetes. 

While mass efforts are underway to shape the nutrition and activity behaviors of school-age children, the most successful interventions to optimize maternal and child health may be the ones that start at conception.

References
American College of Obstetricians and Gynecologists (2002). Exercise during pregnancy and the postpartum period. International Journal of Gynaecology and Obstetrics, 77, 1, 79−81.

Cuda-Kroen G. (2011). Baby’s palate and food memories shaped before birth. National Public Radio, August 8, 2011.

Gardner, B. et al. (2011). Changing diet and physical activity to reduce gestational weight gain: A meta-analysis. Obesity Review, 12, 7, e602−620.

Josefson, J. (2011). Excessive pregnancy weight gain raises the risk of having a fat baby. Presented June 7, 2011, at the Endocrine Society’s 93rd Annual Meeting, Boston, Mass.

May, L.E. et al. (2010). Aerobic exercise during pregnancy influences fetal cardiac autonomic control of heart rate and heart rate variability. Early Human Development, 86, 4, 213−217.

Oken, E. et al. (2008). Maternal gestational weight gain and offspring weight in adolescence. Obstetrics and Gynecology, 112, 5, 999−1006.

Oken, E. et al. (2007). Gestational weight gain and child adiposity at age 3 years. American Journal of Obstetrics and Gynecology, 196, 4, 322, e321−328.

Ogden, C.L. et al. (2006). Prevalence of overweight and obesity in the United States, 1999−2004. Journal of the American Medical Association, 295, 13, 1549−1555.

Rasmussen K. and Yaktine, A. (2009). Weight Gain During Pregnancy: Reexamining the Guidelines. Washington, D.C.: Institute of Medicine.

Wrotniak, B.H. (2008). Gestational weight gain and risk of overweight in the offspring at age 7 years in a multicenter, multiethnic cohort study. American Journal of Clinical Nutrition, 87, 6, 1818−1824.

Zavorsky, G.S. and Longo, L.D. (2011a). Exercise guidelines in pregnancy: New perspectives. Sports Medicine, 41, 5, 345−360.

Zavorsky, G.S. and Longo, L.D. (2011b). Adding strength training, exercise intensity and caloric expenditure to exercise guidelines in pregnancy. Obstetrics and Gynecology, 117, 6, 1399−1402.

_____________________________________________________________________

Natalie Digate Muth, M.D., M.P.H., R.D., is a pediatrics resident at UCLA Mattel Children’s Hospital. She’s also mom to two young children, Tommy (3) and Mariella (11 months).


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