Survey Finds Big Drop in Sexual Activity Among Black Teens

HealthDay – 14 hrs ago TUESDAY, July 24 (HealthDay News) -- Black teenagers in the United States have become much less sexually active over the past two decades, and those who do have sex appear to be more likely to use condoms, a new survey has found.

The declines are "dramatic," said report author Laura Kann, who studies adolescent health for the U.S. Centers for Disease Control and Prevention.

The numbers don't disclose anything about why black teens might have changed their behavior. "This tells us what kids do, but not why," Kann said.

Overall, teens of all racial and ethnic groups are about as sexually active as they were a decade ago. And the rate of condom use by teens -- just six in 10 used them the last time they had sex -- hasn't changed much since the 1990s.

By contrast, the numbers for black teens are strikingly different. The percentage who reported ever having sex fell from 82 percent in 1991 to 60 percent in 2011. Kann said the numbers coincide with drops in teen pregnancy and births.

Increased education about HIV/AIDS among blacks, leadership in the black community and a public health focus on black Americans could explain the change, Kann said.

The new CDC teen-sex survey also reveals that:

The percentages of students who've had sex have remained fairly stable over the last 20 years for Hispanic students (49 percent in 2011) and whites (44 percent in 2011).Overall, 47 percent of all teens surveyed said they'd ever had sex, down from 54 percent in 1991. The rate has barely changed since 2001.About one-third of students said they'd had sex within the past three months, and 15 percent said they'd had sex with four or more partners.The percentage of sexually active teens who use condoms grew from 46 percent in 1991 to 60 percent in 2011, although the number hasn't changed much in recent years. Black teens are more likely to use condoms: their rate is 65 percent.

The recent stabilization of condom use could have something to do with less focus on HIV, which has largely become a treatable disease, Kann said. Also, "the percentage of high school students overall who have had HIV education has dropped since 1997. That hasn't helped any either."

The new survey results come from the CDC's National Youth Risk Behavior Survey of students in grades 9 through 12 from both public and private schools. About 15,000 students take the surveys each year.

Jennifer Manlove, area director of Fertility and Family Structure with the Child Trends advocacy group in Washington, D.C., said the survey shows that much of the evolution toward less sexual activity occurred in the 1990s, even among black teens.

"There's been a little bit more since 2000, but not really that much. The big news in the 1990s was the real focus on the AIDS epidemic and a lot of attention given to that," she said.

Dr. David Katz, director of Yale University's Prevention Research Center, said the study "is a mix of good news and persistent causes for concern."

Nearly half of teens in this country are still sexually active, "and a third or more (of those) did not use condoms most recently," he said. "This means that a very large population of our young people remains vulnerable to all of the perils of unprotected sex, HIV included. So this report is not a cause for celebration. It tells of a job that can be done when we address it well, and of a mission far from accomplished that deserves our more devoted attention."

He added: "No child should get HIV because our society is squeamish about the readily available means of preventing that."

The survey findings were scheduled to be released Tuesday at the International AIDS Conference in Washington, D.C., and published in the CDC's Morbidity and Mortality Weekly Report.

More information

For more about teen sexual health, visit the U.S. National Library of Medicine.

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Snacking and BMI linked to double effect of brain activity and self-control

ScienceDaily (July 23, 2012) — Snack consumption and BMI are linked to both brain activity and self-control, new research has found.

See Also:Health & MedicineDiet and Weight LossBrain TumorObesityMind & BrainDieting and Weight ControlIntelligencePsychologyLiving WellReferenceBody mass indexOverweightAppetiteLimbic system

The research, carried out by academics from the Universities of Exeter, Cardiff, Bristol, and Bangor, discovered that an individual's brain 'reward centre' response to pictures of food predicted how much they subsequently ate. This had a greater effect on the amount they ate than their conscious feelings of hunger or how much they wanted the food,

A strong brain response was also associated with increased weight (BMI), but only in individuals reporting low levels of self-control on a questionnaire. For those reporting high levels of self-control a stronger brain response to food was actually related to a lower BMI.

This study, which is now published in the journal NeuroImage, adds to mounting evidence that overeating and increased weight are linked, in part, to a region of the brain associated with motivation and reward, called the nucleus accumbens. Responses in this brain region have been shown to predict weight gain in healthy weight and obese individuals, but only now have academics discovered that this is independent of conscious feelings of hunger, and that self-control also plays a key role.

Following these results, academics at the University of Exeter and Cardiff have begun testing 'brain training' techniques designed to reduce the influence of food cues on individuals who report low levels of self-control. Similar tests are being used to assist those with gambling or alcohol addiction.

Dr Natalia Lawrence of Psychology at the University of Exeter, lead researcher in both the original research and the new studies, said: "Our research suggests why some individuals are more likely to overeat and put on weight than others when confronted with frequent images of snacks and treats. Food images, such as those used in advertising, cause direct increases in activity in brain 'reward areas' in some individuals but not in others. If those sensitive individuals also struggle with self-control, which may be partly innate, they are more likely to be overweight. We are now developing computer programs that we hope will counteract the effects of this high sensitivity to food cues by training the brain to respond less positively to these cues."

Twenty-five young, healthy females with BMIs ranging from 17-30 were involved in the study. Female participants were chosen because research shows females typically exhibit stronger responses to food-related cues. The hormonal changes during the menstrual cycle affect this reaction, so all participants were taking the monophasic combined oral contraceptive pill. Participants had not eaten for at least six hours to ensure they were hungry at the time of the scan and were given a bowl containing 150 g (four and a half packets) of potato chips to eat at the end of the study; they were informed that potato chip intake had been measured afterwards.

Researchers used MRI scanning to detect the participants' brain activity while they were shown images of household objects, and food that varied in desirability and calorific content. After scanning, participants rated the food images for desirability and rated their levels of hunger and food craving. Results showed that participants' brain responses to food (relative to objects) in the nucleus accumbens predicted how many potato chips they ate after the scan. However, participants' own ratings of hunger and how much they liked and wanted the foods, including potato chips, were unrelated to their potato chip intake.

This study was funded by the Wales Institute of Cognitive Neuroscience.

What this study shows:

Brain responses to food images vary considerably between individuals. Brain responses to food images but not conscious feelings of hunger or desire to eat predict subsequent potato chip consumption. Individuals' reported levels of self-control influence whether this brain response is associated with a higher or lower BMI.

What this study does NOT show:

Brain responses to food cues cause overeating. The associations reported here are true in everyone -- only healthy young women were included. Whether our brain response and levels of self-control are learned or innate.Share this story on Facebook, Twitter, and Google:

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Physical activity needed to reap benefits of dietary restriction

ScienceDaily (July 2, 2012) — Fruit flies on dietary restriction (DR) need to be physically active in order to get the lifespan extending benefits that come from their Spartan diet. If the same axiom holds true in humans, those practicing caloric restriction in hopes of living longer need to make sure they eat enough to avoid fatigue.

See Also:Health & MedicineFitnessHealthy AgingDietary SupplementPlants & AnimalsBiologyGenetically ModifiedCell BiologyReferenceCalorie restricted dietDetox dietAnaerobic exerciseGlycogen

According to research at the Buck Institute, flies on DR shift their metabolism toward increasing fatty acid synthesis and breakdown, specifically in muscle tissue. "Dietary restriction is known to enhance spontaneous movement in a variety of species including primates, however this is the first examination of whether enhanced physical activity is necessary for its beneficial effects," said Buck faculty Pankaj Kapahi, PhD, who runs the lab where the research took place. "This study establishes a link between DR-mediated metabolic activity in muscle, increased movement and the benefits derived from restricting nutrients," he said, adding that flies on DR who could not move or had inhibited fat metabolism in their muscle did not exhibit an extended lifespan. "Our work argues that simply restricting nutrients without physical activity may not be beneficial in humans," said Kapahi.

The research is published in the July 3, 2012 edition of Cell Metabolism.

The research also points to a potential target that could yield a drug that mimics the beneficial effects of DR. Lead author, Subhash D. Katewa, PhD, Buck Institute staff scientist, said flies genetically engineered to overexpress the circulating peptide AKH (the fly equivalent of glucagon in mammals) showed increased fat metabolism, spontaneous activity and extended lifespan even though their diet was unrestricted. AKH plays a critical role in glucose and lipid metabolism. "Our data suggests that DR may induce changes in muscle similar to those observed under endurance exercise and that molecules like AKH could serve as potential mimetics for DR that enhance activity and healthspan," said Katewa.

"A better understanding of the dynamics of fat metabolism is needed in order to clarify its role in aging and disease," Katewa said. "These current results suggest that enhanced fat metabolism could help slow aging and the onset of age-related disease."

Contributors to the work: Other Buck Institute researchers involved in the study include Marysia Kolipinski, and Simon Melov. Other collaborators include Fabio Demontis and Norbert Perrimon, Department of Genetics, Harvard Medical School, Boston; Allan Hubbard, School of Public Health, Division of Biostatistics, University of California, Berkeley; and Matthew S. Gill, Department of Metabolism and Aging, The Scripps Research Institute, Jupiter, FL. The work was funded by grants from the American Federation of Aging Research, and the National Institutes of Health.

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Brain scans can predict weight gain and sexual activity, research shows

ScienceDaily (Apr. 17, 2012) — At a time when obesity has become epidemic in American society, Dartmouth scientists have found that functional magnetic resonance imaging (fMRI) brain scans may be able to predict weight gain. In a study published April 18, 2012, in The Journal of Neuroscience, the researchers demonstrated a connection between fMRI brain responses to appetite-driven cues and future behavior.

See Also:Health & MedicineDiet and Weight LossBrain TumorObesityMind & BrainDieting and Weight ControlPsychologyBrain InjuryLiving WellStrange ScienceReferenceFunctional neuroimagingBone scanMirror neuronSleep deprivation

"This is one of the first studies in brain imaging that uses the responses observed in the scanner to predict important, real-world outcomes over a long period of time," says Todd Heatherton, the Lincoln Filene Professor in Human Relations in the department of psychological and brain sciences and a coauthor on the study. "Using brain activity to predict a consequential behavior outside the scanner is pretty novel."

Using fMRI, the researchers targeted a region of the brain known as the nucleus accumbens, often referred to as the brain's "reward center," in a group of incoming first-year college students. While undergoing scans, the subjects viewed images of animals, environmental scenes, appetizing food items, and people. Six months later, their weight and responses to questionnaires regarding interim sexual behavior were compared with their previously recorded weight and brain scan data.

"The people whose brains responded more strongly to food cues were the people who went on to gain more weight six months later," explains Kathryn Demos, first author on the paper. Demos, who conducted the research as part of her doctoral dissertation at Dartmouth, is currently on the research faculty at the Warren Alpert Medical School of Brown University.

The correlation between strong food image brain responses and weight gain was also present for sexual images and activity. "Just as cue reactivity to food images was investigated as potential predictors of weight gain, cue reactivity to sexual images was used to predict sexual desire," the authors report.

The paper stresses "material specificity," noting that the participants who responded to food images gained weight but did not engage in more sexual behavior, and vice versa. The authors go on to say that none of the non-food images predicted weight gain.

Heatherton and William Kelley, associate professor of psychological and brain science and a senior author on the paper, have a longstanding interest in psychological theories of self-regulation, also called self-control or willpower.

"We seek to understand situations in which people face temptations and try to not act on them," says Kelley.

The researchers note that the first step toward controlling cravings may be an awareness of how much you are affected by specific triggers in the environment, such as the arrival of the dessert tray in a restaurant.

"You need to actively be thinking about the behavior you want to control in order to regulate it," remarks Kelley. "Self-regulation requires a lot of conscious effort."

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