FRIDAY, Sept. 21, 2012 (HealthDay News) -- A trio of new studies finds that people with certain genetic makeups are more susceptible to weight gain when drinking sugar-sweetened beverages. And replacing these drinks with water or diet beverages can prevent weight gain or lead to weight loss.
The findings come on the heels of New York City's controversial ban last week on selling large, sugary drinks in restaurants and other venues.
"There is now convincing evidence that soda and juice are fattening, and the average U.S. kid gets almost three times as many calories from sugary drinks as we gave in our study," said the senior author of one of the studies, Martijn Katan, an emeritus professor of nutrition at VU University, in Amsterdam.
The sugar-sweetened beverage in Katan's study was 104 calories. According to company websites, a single 8-ounce can of Coca-Cola Cherry contains 100 calories, as does an 8-ounce can of Pepsi.
"Sugary beverages can affect body weight quite quickly," said the senior author of another study, Dr. David Ludwig, director of the New Balance Foundation Obesity Prevention Center at Boston Children's Hospital.
The good news, Ludwig said, is that teens seem to be willing to change what they drink if other options are readily available.
All three studies were released online Sept. 21 in the New England Journal of Medicine.
Ludwig's study included 224 overweight and obese teens who regularly consumed sugar-sweetened beverages. The teens were assigned randomly to either the intervention group or the control group. The researchers didn't provide any nutrition education, but those in the intervention group received regular deliveries of non-caloric beverages, such as water, sparkling water and artificially sweetened diet drinks, for a year. Parents also received monthly phone calls to discuss beverage consumption.
At the start of the study, both groups averaged 1.7 servings of sugar-sweetened drinks daily. At one year, that number was almost zero in the intervention group. The control group reported drinking less as well. At one year, they were consuming 0.9 servings of sugar-sweetened drinks each day.
Overall, those in the intervention group gained 4 pounds less than those in the control group during the first year, Ludwig said. He noted that the weight effect was especially strong for Hispanics. Hispanic teens in the intervention group gained 14 pounds less than those in the control group.
"If you're at risk of obesity because of your genes and you drink sugary beverages, you will gain weight," Ludwig said.
The intervention stopped at one year, but the researchers followed up at two years. They found that those in the intervention group were consuming half the amount of sugar-sweetened beverages as the other teens. Those in the intervention group did see a slight increase in their weight during the second year.
Katan's study included nearly 650 normal-weight children between the ages of 4 and 11 years. They were randomly assigned to drink 8 ounces of an artificially sweetened beverage or a similar sugar-sweetened beverage with 104 calories. The beverages were placed in masked containers so the children didn't know who was drinking which product.
After 18 months, children who drank the artificially sweetened beverages were about 2 pounds lighter than those who drank the sugar-sweetened drink.
The final study analyzed genetic risk and the intake of sugar-sweetened drinks, and found that people who have genes that predispose them to becoming overweight appear to be more likely to gain weight when consuming sugar-sweetened drinks than people without the genetic predisposition.
"Soda is the single biggest villain in the obesity epidemic. It's all calories and zero nutrition," said Dr. Steven Safyer, president and CEO of Montefiore Medical Center in New York City. "You take in a significant number of calories, and then you still have to eat. If you compare it to french fries, which have at least a little nutrition, you can't eat those all day long -- you'd get sick. But you can drink soda all day long."
The American Beverage Association (ABA) acknowledges that obesity is a significant problem, but doesn't agree that sugar-sweetened beverages are the root cause of the problem.
"Obesity is a serious and complex public-health issue facing our nation and the rest of the world, and we all must work together to solve it," the ABA said in a written statement. "We know, and science supports, that obesity is not uniquely caused by any single food or beverage."
The ABA also noted that many overweight people don't drink sugar-sweetened beverages at all.
Katan recommended that parents think of sugar-sweetened beverages as a treat, instead of a routine way to meet the body's thirst needs. He said water is the best drink to quench thirst.
Safyer and Ludwig said diet sodas can be an option, particularly as a transitional drink from sugar-sweetened beverages to water. Ludwig added that his group is currently doing a trial to compare water and other unsweetened beverages to artificially sweetened beverages to see if there are any weight differences.
Ludwig added that policy-makers could help, for instance, by putting an excise tax on sugar-sweetened beverages and removing sugar-sweetened beverages as an approved purchase for people on food stamps. He pointed to a recent study that found that $2 billion is spent on sugar-sweetened beverages each year in government food-assistance programs.
To get advice on preventing obesity in children, visit the U.S. Centers for Disease Control and Prevention.