When we rip open a 100-calorie snack pack, few of us have an idea of how much energy that really is–or how much walking, biking, or schlepping groceries it will take to burn it off. But what if nutrition labels included descriptions of how much exercise you’d need to burn off that candy bar?
One recent study explored that possibility by testing the effects of signs describing in one of three different ways the energy contained in a sugary drink. Researchers found that a sign that said “Did you know that working off a bottle of soda or fruit juice takes about 50 minutes of running?” halved the number of drinks purchased from a drink cooler by African American teenagers, while signs that mentioned calorie count or percentage of total recommended calorie intake did not have a significant effect. Though the study was pretty small, and thus should be verified with larger studies, the effect seems plausible, given that exercise is a much more concrete measure of energy value than calories. Some health campaigns have in fact already taken up this tactic: if you’re a New Yorker, you may have noticed subway ads using exactly this strategy, linking the calories in a 20-oz soda with the three-mile walk between Yankee Stadium and Central Park. (more…)
As income rises, the frequency of fast food visits rise as well, at least until income hits $60,000 a year; sit-down restaurant visits just keep on rising. (The y axis is frequency of visits.)
Obesity rates in the United States are highest among the poor, and high up on most lists of reasons why, you’ll find the truism that fast food is cheap food, and the poor, who can’t afford healthier fare, are its main consumers. A new study suggests, however, that the people eating the most fast food are middle class, with incomes as high as $60,000 a year. Using a national database of about 5,000 people, researchers at UC Davis found that the frequency of people’s visits to fast-food restaurants increased with rising household income until $60,000, when frequency started to go down (though, interestingly, people making more than $100,000 still went to fast food more than those making $20,000). Visits to sit-down restaurants, on the other hand, increased with rising income and just kept on growing.
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A Gallup poll reports that on average Americans weigh almost 20 pounds more than they did in 1990, based on the self-reports of more than 1,000 people. The average man weighs 196 pounds while the average woman is 160 pounds. And most of us—62 percent—are already overweight or obese.
But that doesn’t mean we’re ready to come right out and admit it, at least not to a telephone pollster. When asked how they would describe their own weight, only 39 percent of Americans described themselves as “overweight,” while 56 percent reported their weight was “about right.” Neither of these metrics have changed very much since the poll was first given 21 years ago.
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An experimental drug causes obese monkeys to lose weight and improves their metabolic function by depriving their fat of its blood supply, researchers reported yesterday in Science Translational Medicine, offering hope that such drugs could help battle obesity in people, as well.
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Researchers have long suspected that living in a bad neighborhood can be hazardous to your health—whether because of poor access to health care and a paucity of areas to exercise in and stores that sell healthy food, or some combination of other factors, living in a poor area means you have a disproportionate chance of becoming ill and obese. But how can you tell whether that effect is intrinsic to poverty, or whether it can be reversed if people move into more well-off neighborhoods? With a giant, long-term study that gives families in poor neighborhoods a chance to move to other areas.
The results of such a study, conducted by the US Department of Housing and Urban Development, have now been published, and they show that moving from low-income housing projects to a neighborhood with less than 10% of people living below the poverty line does have a positive effect on health. (more…)
What’s the News: Childhood obesity rates have escalated dramatically in recent years, in concert with nationwide explosion that has 34% of American adults falling into that category.
Now, scientists writing in the July 13 issue of the Journal of American Medical Association argue that much as feeding kids too little is considered child neglect, so should be feeding them too much. And if the former is grounds for removing them from their families, then the former may be as well.
As you can imagine, in the last 24 hours, numerous commentators have responded, and the ensuing debate touches on the causes of obesity and the difficulty of treating such a pervasive, devastating problem.
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What’s the News: Fitting in is a perennial problem for almost everybody, especially immigrants and their children (for more, see The Joy Luck Club). And anxiety about food is definitely part of it: when your friends think your mom’s home cooking is weird, well, maybe you’ll just pretend you don’t like it either. In fact, maybe you’ll eat more French fries and pizza than is entirely healthy to fit in, something that might explain why newly arrived immigrants balloon to the rest of the U.S. population’s levels of obesity in just 15 years. In a study designed to see how being perceived as un-American changed peoples’ food choices, scientists behaved badly and then brought out the menus.
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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.
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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.
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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]
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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]
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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.
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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.
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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.
Says Biro:
“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.
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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].
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