Generating Obesity

The obesity epidemic was the topic of the Public Advocacy Forum at the Society for Neuroscience annual meeting on Wednesday, and it was nearly two hours of scary data with a little bit of hope.

You've probably already heard many of the statistics: In the United States, 34 percent of adults over age 20 are classified as obese (body mass index score of 30+, normal is 18.5-25); their healthcare issues cost an estimated $270 billion each year. In the past 20 years, we went from no state having an obesity rate over 14 percent to no state having an obesity rate under 20 percent. Fifteen percent of kids today are overweight, with another 13 percent obese—and 4 percent obese II (BMI of 35+). And on and on.

But for me, the scariest data was on how a tendency toward obesity—and related risks for diabetes, hypertension, and other troubles—may be transmitted parent to child, and on to grandchild. And it's not all on the moms, either.

Research presented by Teresa Reyes of the University of Pennsylvania suggested that maternal obesity leads to the risk of higher BMI, fat accumulation, hyperglycemia, insulin resistance, and heart disease. "Some of the effects are brain-related," she said, "and relate to later risk of obesity." Researchers have found these results in rodents and other primates, as well as humans.

In rats, said Reyes, "A maternal 'junk food' diet in pregnancy and lactation promotes an exacerbated taste for junk food and a greater propensity for obesity in offspring," who show a stronger-than-average preference for sugar and fatty foods. On the other hand, in humans, mothers who drank carrot juice during pregnancy and lactation produced babies who, in the main, also preferred the taste of carrots.

A mother's prenatal food choices affect not only her child; the child's sperm or eggs also develop in the womb, and will pass the traits on to the grandchildren. In the rat studies, if the high-fat-eating mother has a boy, its offspring also will be fatter, no matter the size of his mate.

Reyes says there are a lot of questions still to be answered. Are these changes reversible? What is the critical period (before pregnancy, gestation, first trimester)? Is one sex more vulnerable to another for certain risk factors? "Nearly every study is finding important sex differences," she said.

Surgeon John Kral, a professor at SUNY Downstate Medical Center, described research in macaque monkeys that suggests that a pregnant mother's "food insecurity" can create brain changes that can lead to obesity. Monkey moms who were fed irregularly for only 14 days of their 165-day gestation period gave birth to baby monkeys who grew up to be obese. About 15 percent of people in the United States last year reported "food insecurity"; Kral suggested we might investigate whether the pattern fits for human offspring, as well. (See also the story of the Dutch Hunger Winter.)

"Acute and periodic undernutrition build adaptive mechanisms," Kral said. We have a lot of adaptive mechanisms, but not for obesity. "There are no physiological ways of getting rid of that excess."

Kral also described the effects of what he called "a low-fat diet imposed through surgery," involving gastric bands or diversion surgery. Researchers studied women who had given birth, had the surgery, then (usually years later) given birth again. Children born pre-surgery showed high BMIs and high rates of obesity, hypertension, and other metabolic problems. Children born after surgery showed only a small reduction in average BMI compared with their older siblings—but no higher risk for metabolic problems or obesity.

"We've followed them into their 20s," Kral said. "Obesity surgery improves maternal health, fetal outcome, and child health. It prevents obesity." He's not suggesting we run out and all get lap-banded, though: Obesity surgery carries health risks. (See more on pregnancy after bariatric surgery.)

Kral suggests that every fertile woman have pre-conception education, explaining how metabolism works and how her decisions will affect any future children. Women should start having prenatal visits as soon as they know they are pregnant, not wait three or four months for a first visit. Kral also suggests that as soon as possible after conception, women receive food vouchers until they give birth. "Then food insecurity is taken out of the equation."

Parents want their kids to do well, but they may not realize how their pre-natal food choices can affect the future.

"The kids who are the least fit score the worst on standardized tests," no matter their socioeconomic staus, said Antonio Convit of New York University, including tests of intellectual function, IQ, reading, spelling, working memory, attention, and focus. "I'm not suggesting that these kids are stupid, but they don't do as well on cognitive tasks. Who would want their kid to perform 10 percent less than his potential just because he's carrying extra weight?"

David S. Ludwig of Harvard and Bruce McEwen of Rockefeller University also took part in the forum, which was organized by McEwen. Video of the full 2-hour session is on SfN's YouTube page.

–Nicky Penttila

2 responses

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