LONDON -- A study by British researchers suggests that school programs that discourage the consumption of "fizzy" drinks are effective in reducing obesity.

According to the study, published on the Web site of the British Medical Journal, a one-year "ditch the fizz" campaign in six British schools in led to a drop in the percentage of elementary school children who were overweight or obese.

Fifteen classes took part in the program, and 14 acted as a control group. The children completed diaries of drinks consumed, and body mass index was measured at six and 12 months.

The improvement in obesity rates occurred after a modest reduction in soft drink consumption -- less than a can a day. Both groups of children drank more water during the program.

While there's a growing movement against soft drinks in schools, until now, there have been no studies showing that efforts to cut children's fizzy drink consumption would do any good.

The researchers said their study shows that for most people, obesity is preventable.

"Our intervention was simple, involved no teacher training, and could be easily implemented by a health educator working in several schools," the researchers said.

The British Soft Drink Association disputes the implications of the results. It noted the average daily consumption of carbonated soft drinks was cut by about 35 calories.