I often refer to it, so I dug up this report from the London Daily Telegraph, dated July 8, 2008.
Scientists believe the simple act of writing down everything they eat can encourage people to become stricter about their calorie control.
The study, one of the largest of its kind, involved more than 1,700 volunteers over six months.
Those who wrote a diary of what they ate seven days a week dropped an average of almost 18 pounds over the course of the experiment.
By contrast, those who kept no detailed record of their eating habits had an average weight loss of almost 9 pounds, the study bv researchers at the Kaiser Permanente's Center for Health Research, in Oregon, shows.
Dr Jack Hollis, who led the study, said: "The more food records people kept, the more weight they lost.
"Those who kept daily food records lost twice as much weight as those who kept no records. It seems that the simple act of writing down what you eat encourages people to consume fewer calories."
"These findings provide additional evidence that these standard behavioral strategies are key for successful weight loss," he added.
The participants were asked to keep a food diary and hand them in at weekly support group meetings.
They were also encouraged to a low fat diet rich in fruits and vegetables which has been designed to help heart patients and to exercise moderately for at least 30 minutes every day.
After six months, the average weight loss among the nearly 1,700 participants was approximately 13 pounds, the findings, published in the American Journal of Preventive Medicine, show.
More than two-thirds of the participants, 69 per cent, lost at least nine pounds, enough to reduce their health risks and qualify for the second phase of the study, which lasted 30 months and tested strategies for maintaining the weight loss.
Dr Victor Stevens, who co-authored the study, said that losing just nine pounds could substantially reduce many people's chance of developing diseases like high blood pressure, high cholesterol, diabetes, heart disease and stroke.
Dr Stevens has previously proven that losing as little as five pounds in weight can cut the risk of developing high blood pressure by one fifth.
A spokesman for the British Dietetic Association, said that food diaries were "useful" and that they would recommend them to many people hoping to become slimmer.
"We have certainly found that they have been successful at helping people to lose weight," he said.
