Taking steps to learn more about obesity with smartphones

Photo by Petr Kratochvil

Many of my friends use smartphones to track their steps as they walk about town to grocery shop, grab lunch or just take a break from the computer. Their daily goal is typically 10,000 steps. Now researchers are using this type of data to study public health.

Stanford researchers used step data captured by smart phones to analyze the activity levels of over 700,000 men and women from 111 countries during a 3-month period. Although the data was anonymized, it included key health demographics such as age, gender, height and weight so the research team could calculate each person’s body mass index.

The investigator’s goal was to figure out why obesity is a bigger health problem in some countries than others. As outlined in a paper in Nature, they found that people walked a similar amount each day in countries with little obesity, whereas there was a big activity gap in countries with high levels of obesity — and they dubbed this phenomenon the “activity inequality.”

“If you think about some people in a country as ‘activity rich’ and others as ‘activity poor,’ the size of the gap between them is a strong indicator of obesity levels in that society,” said Scott Delp, PhD, a Stanford professor of bioengineering and of mechanical engineering, in a Stanford news release.

Delp and his colleagues also found a gap in activity levels between genders — men walked more than women — that varied from country to country. Overall, their research identified strong correlations between activity inequality, the gender-activity gap and obesity levels.

How did the United States rank? It was ranked near the bottom for activity inequality due to a large gap between the activity rich and activity poor. It also has a large gender-activity gap and high levels of obesity.

The researchers hope their results will inspire designers to make cities more walkable and pedestrian-friendly. “In cities that are more walkable everyone tends to take more daily steps, whether male or female, young or old, healthy weight or obese,” explained Jennifer Hicks, director of data science for Stanford’s Mobilize Center.

This is a reposting of my Scope blog story, courtesy of Stanford School of Medicine.

Stanford expert calls for more targeted anti-obesity policies

U. S. Department of Agriculture's helps educate shoppers about the value of food labeling in December 1975. Photo courtesy National Archives and Records Administration.
U. S. Department of Agriculture helps educate shoppers about the value of food labeling in 1975. Photo courtesy National Archives and Records Administration.

Reality TV shows like “The Biggest Loser” are popular in part because the audience can relate to the participants — more than two-thirds of adults and about one-third of children and adolescents are obese or overweight in the US. The Surgeon General and the Centers for Disease Control and Prevent have declared obesity to be a national epidemic and a major contributor to leading causes of death, including heart disease, stroke, diabetes and some types of cancer.

Although our country is committed to finding solutions to the increase in obesity, public policies have fallen short, according to Deborah Rhode, JD, a Stanford law professor and legal ethics scholar. In a recent journal article, she wrote:

Many policy responses have proven controversial, and those most often recommended have frequently faced an uphill battle at the federal, state, and local level. At the same time that obesity rates have been rising sharply, many jurisdictions have resisted, or rolled back, strategies such as soda taxes or regulation of advertising directed at children.

In the journal article, Rhode evaluates anti-obesity policies, including calorie disclosure requirements, taxes or bans on sugar-sweetened beverages, food stamp modifications, zoning regulations, children’s marketing restrictions, physical activities initiatives, food policies and education. She suggests that a more targeted approach is needed to combat obesity. For instance, Rhode recommends creative zoning regulations that restrict the location of fast-food restaurants near schools while encouraging healthy food retailers in underserved neighborhoods.

In a Stanford news release, Rhode noted that the first lady Michelle Obama’s “Let’s Move!” campaign against childhood obesity applies to politics as well as physical activity. Rhode summarized, “Although we need more evaluation of policy strategies, we know enough about what works to chart a course of reform. We should act now on what we know.”

This is a reposting of my Scope blog story, courtesy of Stanford School of Medicine.

Girls Entering Puberty Earlier

Courtesy of Cavale via Creative Commons

Girls have always gone through puberty at varying ages. When I was 11 years old, I looked like a flat-chested scrawny little girl. Meanwhile, my best friend Judy at that age looked like a grown woman, basically the same as when she graduated from high school. This was a real problem for large-chested Judy because older men frequently hit on her, probably having no idea that she was only 11 years old and unprepared to cope with their advances.

Early maturation in girls is associated with lower self-esteem, less favorable body image, and greater rates of eating problems, depression, suicide attempts and risky behavior. Beyond the emotional issues, girls that go through puberty early are also at higher risk for some medical problems such as breast cancer, endometrial cancer, pre-diabetes and elevated blood pressure. These emotional and health concerns appear to worsen as the age of puberty onset lowers.

Although the timing of puberty always varies between different girls, the average age when girls enter puberty has fallen in the past two decades. A lot of reports and controversy have surrounded this finding, starting with a study published in 1997 in Pediatrics. Why this is happening is not fully understood. Ongoing studies are trying to determine whether this trend is continuing or whether the age of puberty onset for girls has stabilized.

The results of a new study on the timing of breast development in girls were just reported in Pediatrics by a research team led by Dr. Frank Biro, director of adolescent medicine at Cincinnati Children’s Hospital Medical Center. Dr. Biro and his colleagues studied 1239 girls ages 6 to 8 who were recruited from 3 diverse sites: East Harlem in New York, Cincinnati metropolitan area, and San Francisco Bay Area. The recruited group was 34% white, 31% black, 30% Hispanic, and 5% Asian. The data came from interviews with caregivers and physical examinations of the girls. Great care was taken to ensure that the examinations were performed by only well-trained certified staff, using identical well-established guidelines for determining the onset of puberty.

The researchers found that more girls are starting puberty at the age of 7 or 8 than previously reported 10 to 30 years earlier. At 7 years, 10.4% of white, 23.4% of black, and 14.9% of Hispanic girls had enough breast development to indicate the beginning of puberty. At 8 years, 18.3% of white, 42.9% of black and 30.9% of Hispanic girls had sufficient breast development. In comparison, the 1997 study found only 5% of white girls and 15.4% of black girls to have entered puberty at the age of 7.

So the new study shows that the age of entering puberty is continuing to fall for young girls, especially white girls. However, black and Hispanic girls still mature at younger ages than white girls. The cause of this concerning trend is not fully understood. Increased rates of obesity are thought to play a significant role, because body fat can produce sex hormones. Environmental chemicals are also suspected, since they might mimic effects of estrogen and speed up puberty, but this is still under study. Genetics may also play a role.

Breast Cancer and the Environmental Research Centers (BCERC) were established in 2003 as a consortium to study some of these issues, in partnership with the National Institute of Environmental Health Science (NIEHS) and National Cancer Institute (NCI). As Dr. Biro summarizes, “I think we need to think about the stuff we’re exposing our bodies to and the bodies of our kids. This is a wake-up call, and I think we need to pay attention to it.”