A study by the Kaiser Permanente Center for Health Research released Tuesday said keeping a daily food diary helped overweight people lose weight twice as much as those who did not keep a record of what they ate.

According to Victor Stevens, senior investigator at Kaiser, the food diary provides the dieter an awareness of what he is taking in, which could track the source of extra calories.

Kaiser observed for two years 1,685 men and women who were battling the bulge. After half a year of maintaining a food log, they lost an average of 12.5 pounds. Participants who faithfully recorded their food intake lost between 13 to 20 pounds over six months, while those who did not have a food diary shed only an average of 9 pounds.

The food log also provides dieters a good snapshot of their eating habits. According to Sharon Meyes, a nutrition therapist at the Institute for Health and Healing of the California Pacific Medical Center, "People are quite surprised by what they find... They have this idea that they're eating two or three slices of bread in a day and then they realize they're eating six. Writing everything down brings us back to reality."

The study will be published by the American Journal of Preventive Medicine.