Super-Sized Youth: The Ongoing Epidemic of Childhood Obesity

As childhood obesity reaches epidemic proportions, ailments once confined to adults are being diagnosed in younger patients. New studies show that childhood adversities and PFC exposure are contributing factors to this growing scourge.

The devastating physical and emotional effects of childhood obesity have been increasingly well documented as the rate of overweight and obesity skyrocketed in the last half of the 20th century on into the first half of the 21st century. At its peak, one in three children, ages two to 19 years, were considered overweight or obese, based on body mass index (BMI) at the 95th percentile or higher of the Centers for Disease Control and Prevention growth charts. “Childhood obesity has reached epidemic proportions,” says Steven J. Czinn, MD, professor and chair of the University of Maryland School of Medicine’s Department of Pediatrics. “The culture of many of today’s youth is not centered on physical activity or eating healthy foods.”

With childhood obesity increasing, serious medical conditions once considered the provenance of adulthood, such as diabetes, elevated blood pressure and cholesterol levels, and depression, as well as insidious effects such as low self-esteem and body dysmorphia began to comorbidly affect children and adolescents, and childhood obesity captured the clinical research world’s attention. Although rates have come down slightly in the last couple of years, especially in the very young, the problem paradoxically continues to grow as more and more complications come to light. Now hovering at about 17% of U.S. children and adolescents, childhood obesity causes a disproportionate share of immediate and longterm adverse health effects.

Truncated Lifespan

Although morbidity and comorbidities of obesity are common research avenues, obesity’s eff ects on life expectancy have been unclear. To examine the relationship between BMI at adolescence and mortality rate, a team of researchers headed by Amir Tirosh, MD, PhD, of the Brigham and Women’s Hospital and Harvard School of Public Health, Boston, launched a prospective nationwide longitudinal cohort study of 2,159,327 Israeli adolescents between 1967 and 2011. The largest analysis ever conducted on the impact of childhood and adolescent obesity on all-cause mortality rates in midlife, the study comprised 43 million person-years of follow-up, by linking with Ministry of Interior mortality records.

Their chilling findings, which were published in The Journal of Clinical Endocrinology & Metabolism, show that although, overall, people across the globe live longer today than they did 50 years ago, those who were overweight and obese as teenagers did not similarly gain in life expectancy — early mortality rates in 2011 stayed the same as those in the 1960s. For men, the prognosis is even worse. Across all BMI ranges, including what is currently considered normal, men are three times more likely to die than women before age 50. “If such a trend continues, the high rates of childhood and adolescence overweight and obesity are likely to adversely affect life expectancy,” Tirosh says.

New Complications Emerge

Such far-reaching consequences are shocking enough; Add to them a new finding that environmental health hazards pose particular risks for overweight and obese children, and the picture grows bleaker for this acutely at-risk population. As part of the 1997 European Youth Heart Study, researchers led by Clara Amalie G. Timmermann, M.Sc., from the Syddansk Universitet Odense, in Denmark, sampled plasma from 499 eight- to 10-year-old Danish children to conduct perfluorinated/polyfluorinated compound (PFC) analysis, using high-performance liquid chromatography and mass spectrometry. Recently, the endocrine disruption and resultant health risks caused by PFCs, industrial chemicals used in a variety of consumer products, have led to decreased commercial use, but, thanks to their long half-lives, PFCs accumulate in air, dust, and water. Children tend to have higher serum concentrations of PFCs, likely due to hand-to-mouth transfer.

The researchers’ study, published in The Journal of Clinical Endocrinology & Metabolism, is the first to focus specifically on metabolic changes in children exposed to PFCs and shows that they exhibit early stages of metabolic syndrome, consistent with recent findings in American adults. Using the homeostasis model assessment (HOMA), levels of plasma glucose, insulin, triglycerides, adiponectin, and leptin were used to estimate insulin resistance and pancreatic β-cell function.

“Our study shows that increased exposure to these chemicals is associated with changes in serum concentrations of insulin and triglyceride in overweight children,” Timmermann says. “The results suggest that these highly persistent chemicals could represent an important health hazard, which needs to be addressed in further studies,” she continues. Because no link was found between PFCs and glycemic control indices among normal-weight children, the implication is additionally that overweight and obese children may be uniquely vulnerable to endocrinedisrupting substances and their associated complications.

Adversity-Obesity Link: A Troubling New Cause

With rates of childhood obesity so persistently high and the impact of the condition so catastrophic, prevention has taken the spotlight. However, as researchers and clinicians well know, the etiology of obesity is nothing if not complex. From October 2009 to April 2012, a team of researchers led by Christos S. Mantzoros, MD, DSc, PhD, of the Harvard Medical School in Cambridge, Mass., investigated the pathophysiologic mechanism underlying the association between early-life adversity (physical, emotional, or sexual abuse; neglect; and even parental divorce) before age 18 and obesity, diabetes, and metabolic syndrome in a cross-sectional study of 95 adults aged 35–56. The researchers created an adversity score by multiplying the number of adversities by the overall severity of adversity by the overall chronicity of adversity and grouped participants into tertiles (T1–T3). Using multiple linear regression analysis, researchers measured circulating levels of the adipomyokines leptin, adiponectin, and irisin and the inflammatory marker C-reactive protein. In their paper, published in The Journal of Clinical Endocrinology & Metabolism, researchers report that T3, the severest adversity group, demonstrated elevated leptin, involved in satiety regulation, and irisin, involved in energy metabolism, even after adjusting for potential confounders such as gender and race. Decreased levels of the glucose and lipid metabolism modulator adiponectin were additionally reported.

“These effects of early-life adversity occurred above and beyond any effects of nutrition or exercise on obesity,” Mantzoros says, suggesting that leptin and irisin possibly directly mediate the link between early-life adversity and the pathogenesis of obesity perhaps via threefold disruption of the hypothalamic–pituitary–adrenal axis, the immune system, and metabolic regulation systems. “Primary care doctors and endocrinologists should keep early-life adversity in mind as a potential risk factor for the development of central obesity and metabolic syndrome later in life and intensify, as appropriate, lifestyle modification or other prevention measures in this segment of the population,” Mantzoros says.

Czinn agrees that lifestyle modification is the key to thwarting the obesity epidemic and all of its associated complexities: “Through many national and local initiatives, pediatricians and parents alike are working together to change how children and families view exercise and a healthy diet, which will, in turn, dramatically improve the health of an entire generation.”

— Horvath is a freelance writer based in Baltimore. She wrote about the health disparities in thyroid cancer in the March issue.

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