As the waistlines of children in the United States continue to grow, scientists continue to seek causes of the childhood obesity epidemic. One University of Alabama at Birmingham School of Public Health researcher has published a new theory that he says explains why infants in the United States are being born heavier than at any time in our nation's history.
According to the Centers for Disease Control and Prevention, obesity has more than doubled in children and quadrupled in adolescents in the past 30 years. In 2012, more than one-third of children and adolescents were overweight or obese.
"Childhood obesity is the major public health problem of the 21st century and will continue to be until we fully understand why children are becoming obese. My theory offers that understanding," said Edward Archer, Ph.D., postdoctoral fellow in the Nutrition Obesity Research Center and Office of Energetics.
Archer says that previously there were no valid theories as to why children are becoming so obese so rapidly, and that the common notion of "moving too little and eating too much" is simplistic and leads to the stigmatization of a large portion of our population.
Through a meta-theoretic analysis, Archer unified ideas from a number of scientific fields and created a grand narrative, "The Childhood Obesity Epidemic As a Result of Non-Genetic Evolution: the Maternal Resources Hypothesis," published in the November issue of the Mayo Clinic Proceedings.
"This paper is a significant advance in the theory and science of evolution, obesity and health," Archer said. "It synthesizes a century of evidence from fields as diverse as pediatrics, evolutionary biology, anthropology and epidemiology to present a novel theory on the causes of the childhood obesity epidemic."
There are three main findings:
1. Obesity is the result of fat cells' out-competing other tissues for the energy consumed through food.
2. A woman's physical activity and body composition before, during and after pregnancy have evolutionary consequences because both determine not only her metabolism and risk of disease but those of her children, grandchildren and great-grandchildren.
3. Mothers in many subpopulations have evolved past a "metabolic tipping point" that makes obesity and poor physical fitness almost inevitable for their children and their children's children.
"My theory says that obesity is the result of nongenetic evolutionary forces, for example social/cultural evolution, that have led to the competitive dominance of fat cells," Archer said. "Beginning in the 1960s, mothers became increasingly physically inactive, sedentary and heavier. This altered their bodies' metabolism during pregnancy. With less competition between fat and muscle cells due to inactivity, more energy was available to increase the number of fat cells in their unborn children. The result was a dramatic increase in the risk of obesity and disease in infants and children."
Archer says these findings demonstrate that the typically highlighted reasons for childhood obesity are not the root cause, and the issue began with earlier generations.
"My paper demonstrates that gluttony and sloth are not the primary determinants of obesity, and hopefully it will dispel the ignorance that causes good-hearted people to mistakenly think that a child is obese because of a lack of willpower, or because his or her mother does not care enough to provide proper food," Archer said. "Willpower and good intentions cannot compete with evolution."
To halt the continued evolution of obesity, Archer says would-be moms must be physically active throughout their lives -- especially during puberty -- to prepare their metabolisms for pregnancy and have metabolically healthy children. Archer thinks that clinicians must know that preconception and prenatal exercise are essential but underutilized tools in the struggle against obesity.
"Evolution is the cause, and active moms are the cure," Archer said. "Only mothers have the power to change the evolution of obesity."
In hopes of developing effective interventions based on his theory, Archer is building virtual humans -- including pregnant women -- via computational modeling.
"Science can improve the lives of mothers and children, and my theory is a productive first step," Archer said.

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