Researchers have for some time suspected that a tendency to overeating and obesity may actually be “programmed” into children even before birth. It has been consistently observed that children whose mothers were obese and diabetic have a higher risk of being heavier themselves from an early age, and adult obesity can be linked to eating a high-fat diet in childhood.
But there was little information on exactly how and when these patterns are set in infancy, or even before.
Recently a team of scientists at Rockefeller University in New York City has identified how this process occurs in an animal model, in findings that may have implications for understanding obesity in humans as well.
Prenatal obesity in animals
The Rockefeller scientists studied two groups of pregnant rats and their offspring. For the last two weeks of pregnancy, one group of rats was fed a diet moderate in fat, while another group received a diet high in fat. The high-fat diet was discontinued immediately after delivery. The young rats born after the mothers’ two-week high-fat diet ate more, weighed more, and matured earlier sexually than the rats whose mothers were on the moderate diet. At their birth, blood tests showed the high-fat babies already had high levels of triglycerides, and as adults their brains showed higher levels of certain brain peptides that trigger overeating.
Team leader Sarah F. Leibowitz (director of the Laboratory of Behavioral Neurobiology at Rockefeller) reports that the team turned their attention to what was happening in the brains of the developing rat pups in the final week before their birth. In the pups whose mothers ate the high-fat diet, their brains were already producing significantly higher numbers of a certain kind of neuron associated with overeating. In the pups whose mothers were fed moderate fat levels, these neurons did not develop until after birth and were fewer.
It had previously been recognized that in adult animals a diet high in fat causes higher levels of triglycerides in the blood, which in turn trigger the brain to produce more appetite-stimulating orexigenic peptides. The Rockefeller study found that their mothers’ high-fat diet in those final gestational days had caused the rat pups’ brains to develop more of the neurons that produce those appetite-stimulant peptides. They kept those neurons throughout their lives.
Being exposed to their mothers’ high-fat diet actually caused the unborn rats’ brains to develop a propensity to overeating. They were programmed for obesity even before birth.
Implications for obesity in humans
The Rockefeller researchers believe that their research may have profound implications for the understanding of human obesity and the growing epidemic of childhood obesity in particular.
“We’re programming our children to be fat,” concludes Leibowitz. “We’ve shown that short-term exposure to a high-fat diet in utero produces permanent neurons in the fetal brain that later increase the appetite for fat.”
The Rockefeller team published their findings in “Maternal High-Fat Diet and Fetal Programming: Increased Proliferation of Hypothalamic Peptide-Producing Neurons That Increase Risk for Overeating and Obesity,” by Guo-Qing Chang, Valeriya Gaysinskaya, Olga Karatayev, and Sarah F. Leibowitz The Journal of Neuroscience, November 12, 2008, 28(46):12107-12119.
The full text of their report is available here.