What’s the News: Researchers have known for decades that what a woman eats during her pregnancy can impact her child’s weight later in life. Now, a new study shows a possible mechanism for how mom’s diet affects baby’s weight: Epigenetic changes—changes that can increase or decrease the expression of a particular gene but don’t alter the genetic sequence—to a gene involved in fat metabolism can be passed from mother to child during pregnancy.
Most children shed their “baby fat.” But researchers say that in more and more cases, chubby babies (which are about 30 percent of all babies) are primed for obesity later in life.
“We are certainly not saying that overweight babies are doomed to be obese adults,” study researcher Brian Moss, PhD, of Detroit’s Wayne State University tells WebMD. “But we did find some evidence that being overweight at 9 months of age is a predictor of being overweight or obese later in childhood.” [Web MD]
The study followed a group of 7,500 babies born in 2001, classifying them by their position on the baby growth chart as “at risk” (those falling in the 85th to 95th percentile weight group) or “obese” (the 95th and above percentile). When the babies were nine months old and again at the age of two years, the parents filled out surveys about their child’s length and weight, their socioeconomic status, and race. The researchers found that 32 percent of the 9-month-olds were overweight, and 34 percent of the toddlers were. The study was published in the American Journal of Health Promotion.
Researchers have identified 30 genes that play a role in the onset of menstruation in girls. Some of these puberty genes have previously been linked to body weight and fat metabolism, strengthening the connection between the obesity epidemic and the early onset of puberty in industrialized nations.
For the study, published in Nature Genetics, researchers analyzed 32 genome-wide association studies that included more than 87,000 women from the United States, Europe and Australia, and then replicated the results in a further 14,000 women. Of the 30 genes that they found play a role in the timing of women’s first periods, four genes are linked to body mass index, three play a role in metabolism, and three are involved in hormone regulation.
Study co-author, Dr Enda Byrne of the Queensland Institute of Medical Research says the results from this study show that many of the genes that increase risk for weight gain and obesity in adulthood, also influence the onset of puberty. “This supports the idea that the body launches into puberty once it reaches a certain level of nutrient stores and therefore children who are overweight are more likely to undergo early puberty,” says Byrne. [Australian Broadcasting Corporation]
Scientists knew that overweight mothers tend to have more overweight children. But is the same true for fathers? This week in Nature, Margaret Morris and her team demonstrated this effect in male rats, the first time it’s been shown to work in males. The findings are another example of how non-genetic factors, like how much a parent eats, can have a biological impact on offspring.
The researchers put one of their two groups of male rats on a high-fat diet, the other on a normal one. Unsurprisingly, the high-fat rats put on a lot of weight and began to show symptoms of type II diabetes, like insulin resistance and struggles with metabolizing glucose. And then there were their kids:
The real surprise came when Morris’s team went on to examine the obese rats’ female offspring. These too had problems regulating insulin and glucose levels. The healthy fathers, however, had correspondingly healthy daughters. Whether similar defects emerge in sons remains to be seen. [Nature News]
The winners of the Lasker Awards, the top medical prizes given out in the United States, were announced today.
The Laskers, awarded by the Albert and Mary Lasker Foundation, are $250,000 awards generally regarded as good predictors of who will go on to win a Nobel Prize for medicine or chemistry. [ABC News]
The driver of obesity
Douglas Coleman and Jeffrey Friedman took home the prize in the first category, basic medical research. The pair discovered leptin, a hormone that governs body weight and appetite. Its discovery helped to explain parts of obesity that had never been understood.
A study of children has discovered a correlation between obesity and prior infection with a cold virus, called Adenovirus 36. While the link is fairly weak, the tantalizing research suggests a new front on the war on obesity.
The study participants included 124 children between the ages of 8 and 18. Of the 67 obese children involved in the study, 15 had signs of previous infection with the AD36 virus, in comparison with only 4 of the 57 non-obese children. The study was published in the online edition of Pediatrics.
The children who had been previously exposed to the virus (which was indicated by the antibodies to the virus present in their blood) were on average 50 pounds heavier than the non-exposed children. And even within the obese group, those that had been previously exposed to AD36 were an average of 35 pounds heavier.
Girls around the country are starting puberty ever younger, says a new study out in Pediatrics.
Researchers led by Frank Biro studied more than a thousand girls between six and eight years old from New York, Cincinnati, and San Francisco. Their findings: By the age of 7, about 23 percent of black girls, 15 percent of Hispanic girls, and 11 percent of white girls showed enough breast development to be considered pubescent. Those numbers are even more extreme than the findings of a similar 1997 study that seemed to show the age entering puberty was dropping fast.
“In 1997, people said, ‘That can’t be right; there must be something wrong with the study’. But the average age is going down even further” [Los Angeles Times].
The starkness of Biro’s statistics has drawn plenty of attention. But just what it means is a difficult question, because there’s no “ideal” age for entering puberty.
Last spring, researchers confirmed that brown fat—the kind that burns energy rather than storing it and is especially prevalent in newborns—can be found in small pockets in adults, too, and slimmer adults have more of it. This spring, a team says it might have found one of the first steps in activating that fat-burning fat in adults. Their study comes out in Science this week.
Brown fat is packed with energy-producing mitochondria, and babies have a lot of it because it helps them keep warm. Once humans begin to regulate their own body temperature they don’t need as much brown fat anymore, so it gets replaced by energy-storing white fat, which helps store energy but leads to expanded waistlines in this age of affluence.
Testing on mice, the team led by Stephan Herzig upped the use of an enzyme called cyclooxygenase-2 (COX-2). While the enzyme plays a role in many physiological functions, the researchers found that pushing it in mice could induce their white fat to act more like energy-burning brown fat, and their weight dropped by around 20 percent.
“There has been a lot of excitement around brown fat, but … there wasn’t any clear indication that turning up brown fat would make animals lose weight,” says Chad Cowan, a professor in the Department of Stem Cell and Regenerative Biology at Harvard Medical School who studies fat cell development. “What this paper does is make a good link to something that might be clinically beneficial [TIME].
Do you often feel the need for a sweet sugar rush or a moment of bacon-induced bliss? A new study offers evidence that that surge of pleasure is similar to a heroin high, and that eating junk food regularly can significantly change the brain’s chemical make-up, creating junk food addicts who are driven to overeat.
Lead researcher Paul Kenny says it had previously been unclear whether extreme overeating was initiated by a chemical irregularity in the brain or if the behavior itself was changing the brain’s biochemical makeup. The new research by Kenny and his colleague Paul Johnson, a graduate student, shows that both conditions are possible [Scientific American].
For the study, published online in Nature Neuroscience, Kenny and colleagues headed to the grocery store. “We basically bought all of the stuff that people really like — Ding-Dongs, cheesecake, bacon, sausage, the stuff that you enjoy, but you really shouldn’t eat too often,” he said [Reuters]. One set of lab rats was allowed unfettered access to these high-calorie foods, while another rat group was allowed just one hour of access to the junk food per day. Both sets of rats also had the option of eating standard healthy lab rat fare. Finally, a control group of rats were kept on a healthy diet.
The next time a friend says he’s addicted to bacon, you should know he probably isn’t joking. The brains of rats fed only on junk food—like bacon, Ho Hos, cheesecake, and sausage—look similar to the brains of heroin-addicted rats, according to new a study. Pleasure centers in the brains of rats addicted to high-fat, high-calorie diets became less responsive as the binging wore on, making the rats consume more and more food [Science News]. The findings suggest that drug addiction and overeating have similar biological mechanisms, according to the scientists from the Scripps Research Institute. The work is not yet published, but was presented at the Society for Neuroscience’s annual meeting.
The rats fed on junk food displayed a hallmark of addiction. After just five days on the junk food diet, rats showed “profound reductions” in the sensitivity of their brains’ pleasure centers, suggesting that the animals quickly became habituated to the food. As a result, the rats ate more food to get the same amount of pleasure. Just as heroin addicts require more and more of the drug to feel good, rats needed more and more of the junk food [Science News]. To test the depths of the rats addiction, researchers shocked rats every time they ate junk food. Rats that had not previously binged on Ho Hos quickly stopped eating the high-fat foods. However, the fat rats kept eating junk food even though they knew the shock was coming. Now that’s an addiction.
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Image: flickr / asplosh