Three studies find a more positive link between soda and genetic obesity

The number of obese Americans is overwhelming—78 million adults and 12.5 million children—and the numbers are projected to increase. The increasing numbers have scientists and health professionals looking for the causes of increased weight and the steady climb of obesity.

For the first time, three prospective cohort studies provide reproducible evidence that the regular consumption of sugar-sweetened beverages (SSBs) is associated with a greater genetic susceptibility to higher body mass index (BMI) and an increased risk of obesity. This new evidence strengthens the case that sugary beverages are one of the leaders behind the obesity epidemic.

In the past thirty years consumption of SSBs has increased worldwide, being the major source of sugar in the American diet. Studies have found that children’s soft-drink consumption is on the rise, with consumption of these beverages starting at infancy.

There has been a multitude of evidence that supports the link between SSBs, obesity and chronic diseases such as osteoporosis, kidney damage and certain cancers. But there has been little research on whether environmental factors such as drinking sugary beverages influence genetic predisposition to obesity.

This new research was based on data from three large cohort studies: Nurses’ Health Study, Health Professionals Follow-up Study, and in a duplicate cohort Women's Genome Health Study. All participants had filled out food frequency questionnaires detailing their food and drink consumption overtime.

Researchers evaluated data from 6,934 women from the NHS, 21,740 WGHS and 4,423 men from the HPFS.

Participants were divided into four groups according to the amount of sugary beverages they consumed: less than one serving a month, one to four servings a month, two to six servings a week and one serving or more each day. To represent the overall genetic predisposition, a genetic predisposition score was calculated on the basis of the 32 single-nucleotide polymorphisms known to be associated with BMI (weight in kilograms divided by the square of the height in meters).

The results revealed the genetic effects on BMI and obesity risk were double for those who consumed one or more sugary beverages a day in comparison to those who consumed less than one serving a month. The findings suggested that regular consumption of sugary beverages may intensify the genetic risk of obesity.

Dr. Frank Hu, professor of nutrition and epidemiology at HSPH and co-author of this study, stated in a public release: "SSBs are one of the driving forces behind the obesity epidemic. … The implication of our study is that the genetic effects of obesity can be offset by healthier food and beverage choices."

This study appears in the New England Journal of Medicine.

In New York, Mayor Michael Bloomberg has a plan to restrict the sale of sugary soft drinks to cups of no more than 16 ounces in restaurants, movie theaters, stadiums and arenas. The ban was met with harsh criticism from soft-drink giants Coca-Cola and Pepsi.

However, Bloomberg’s plan has sound evidence to support it thanks to researchers from the UV University in Amsterdam.

The 18-month trial involved 641 primarily normal weights from 4 years, 10 months to 11 years, 11 months of age.

Children were randomly assigned to receive either eight ounces per day of a sugar-free, artificially sweetened beverage (sugar-free group) or a similar sugar-containing beverage that provided 104 kcal (sugar group). The beverages had been distributed through school.

Over eighteen months the children in the sugar-free group had gained 13.9 pounds on average, with the children in the sugar group gaining 16.2 pounds.

This study also appeared in the New England Journal of Medicine.

Most of all, the research available indicates the consumption of sugary-sweetened beverages are linked to higher rates of weight gain, obesity and type 2 diabetes.

The Harvard School of Public Health Prevention Research Center (HPRC) is working with the Boston Health Commission, Boston Public Schools and providers of after-school programs, such as the YMCA, Boys and Girls Club of Boston and the Boston Centers for Youth and Families to create environments that are free of sugary drinks.

Academic journal articles that provide evidence for the importance of limiting sugary beverages to improve health and reduce overweight and chronic disease risk are available online at Research Priority Issues.

Slideshow: Just how sweet is it?