Despite over twenty years of research, childhood and adolescent obesity continues to be a hot topic in today’s research environment. One in five American children and adolescents aged 6-19 is obese. The question of “nature” vs. “nurture” frequently comes up among researchers and clinicians, as they continue struggle to identify ways to prevent childhood obesity. For example, some twin studies strongly suggest a genetic role in the development of childhood obesity; however, the recent rapid increase in the prevalence obesity makes changes in lifestyle a more likely culprit. Furthermore, investigations to elucidate the root causes of childhood obesity are directed not only at genetic causes, but also at environmental causes, such as parenting, food patterns, and family structure. In a recent prospective cohort study of mother-child pairs in the US, Dhana et al sought to tease apart potential etiologies of childhood obesity. In this study, authors sought to determine the association of overall maternal lifestyle during their offspring’s childhood and adolescence with the risk of incident obesity.
The Nurses’ Health Study II (NHSII) and the offshoot Growing Up Today Study (GUTS) provide a uniquely large amount of raw data to analyze for trends in childhood obesity. NHSII is a prospective study of over 100,000 female nurses since 1989. GUTS began in 1996, when almost 30,000 children of NHSII participants were enrolled. The 2018 Dhana study included 25,000 GUTS participants born to 17,000 NHSII women and assessed the relationship of the following lifestyle factors in mothers to the risk of developing obesity in their offspring: diet (assessed with an Alternate Healthy Eating Index 2010 diet score), alcohol consumption, physical activity, body mass index, and smoking history. The Alternate Healthy Eating Index 2010 diet score summarizes information on high intake of vegetables, fruits, nuts, whole grains, polyunsaturated fatty acids, and long chain omega 3 fatty acids, and lower intake of red and processed meats, sugar sweetened beverages, trans fats, and sodium.
This study aimed to measure the incidence of new onset obesity amongst GUTS patients during the study period. They found that offspring of women with obesity (BMI ≥ 30) had a relative risk of 3.10 (95% confidence interval 2.69 to 3.57) of developing obesity, compared with children of mothers in normal body weight range (BMI 18.5-24.9). This finding held when adjusted for race/ethnicity, chronic diseases, living status, household income, and educational attainment of spouse/partner.
Study authors also found that offspring of mothers who adhered to all five of the low risk lifestyle factors had a 75% lower risk of developing obesity than those of mothers who adhered to none, which was not overly surprising. This risk was further reduced when both mothers and their children adhered to a healthy lifestyle.
All of the mothers in this study are nurses and are also 96% Caucasian. This study population is much more homogenous than the general population of US mothers, which is a major limitation to this study. It is possible that diet variation would have a greater impact in a more heterogeneous study group. Further, Hispanics and non-Hispanic blacks have the highest prevalence of obesity in the US, so it seems likely that these groups might have different, and potentially worse outcomes in a similar study. Groups underrepresented in this study, such as non-whites and non-health professionals, tend to have a higher prevalence of childhood obesity, so future studies in other populations could shed light on whether and how these same factors play a role for them.
Ultimately, this study does reinforce the concept that maternal lifestyle choices can play a critical role in a child’s overall health and development. It suggests that we cannot simply rely on counseling kids on diet and exercise, or even on counseling parents on how their children should be eating. Rather, it may be that focusing on the mother’s lifestyle, or perhaps that of the whole family, is more effective. As a future family medicine physician, this prospect excites me. Focusing on both mother and child as patients and recognizing how the entire family unit plays a role in the health of a child, seem both necessary and inevitable.
However, I think it is essential to note that these “low risk” behaviors, including healthy diet, physical activity, and smoking habits, are inextricably linked to socioeconomic status. It is one thing for a mother to know that she and her child should be eating lots of vegetables, but another for her to have the money, time, and supplies to actually make that meal happen. As clinicians, it is not enough to counsel our patients on low risk behaviors. Rather, we must ask our patients questions to better understand their means and access. As future clinicians we should strive to help our patients implement these healthy behaviors into their daily lives.