The study was carried out by investigators from Kaiser Permanente's Center for Health Research, and is to be published in the August issue of the American Journal of Preventive Medicine.
The study is one of the largest and longest running weight loss maintenance trials ever conducted, wrote the researchers in a press statement, and is also unique in that a large number of participants (44 per cent) were African Americans who are known to have higher risks for diseases that are made worse by being overweight, such as heart disease and diabetes.
Those who kept regular and frequent food records tended to lose more weight, said lead author Dr Jack Hollis, a researcher at Kaiser Permanente's Center for Health Research in Portland, Oregon, adding that:
"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."
The trial, known as the Weight Loss Maintenance (WLM) trial, was a a randomized trial conducted at four centers to compare different approaches to maintaining weight loss over a period of 30 months. The August paper describes the results from Phase I, the first 6 months of the trial.
1,685 overweight or obese (Body Mass Index or BMI in range 25 to 45 kg/m2) participants aged 25 and over and who were taking blood pressure and/or antidyslipidemia medication (eg cholesterol busters) took part in 20 weekly group sessions to encourage them to restrict their calorie intake, take part in daily moderate to intense physical exercise for half an hour a day, and modify their diet according to the DASH (dietary approaches to stop hypertension) guidelines. The participants were also encouraged to keep daily records of their calorie intake.
After six months, the results showed that:
- 44 per cent of the participants were African American, 67 per cent were women, and 79 per cent were obese (BMI of 30 or more).
- 87 per cent were taking blood pressure medication and 38 per cent antidyslipidemia medication (eg cholesterol busters).
- An average of 72 per cent of the participants attended 20 group sessions.
- The average reported amount of time spent in moderate to intense physical exercise was 117 minutes a week (nearly 2 hours).
- On average the participants kept 3.7 daily food records a week, and consumed 2.9 servings of fruit and vegetables a day.
- The average weight loss among all the participants was about 13 pounds (5.9 kilos).
- More than two-thirds (69 per cent) of them lost at least 9 pounds (4.1 kilos).
- This was enough to reduce health risks and qualify them for Phase II, which lasted 30 months and tested different approaches to maintaining the weight loss.
- All race and gender subgroups lost significant amounts of weight.
- Among African Americans, the average weight loss among men was 11.9 pounds (5.4 kilos) and among women it was 9 pounds (4.1 kilos).
- Among non-African Americans, the average weight loss among men was 18.7 pounds (8.5 kilos) and among women it was 12.8 pounds (5.8 kilos).
- Behaviour such as diet records and physical activity accounted for most of the variation in weight loss, although these links differed by race and gender.
"Successfully achieved clinically significant short-term weight loss in a diverse population of high-risk patients."
More than two thirds of Americans are overweight or obese, said co-author and Kaiser Permanente researcher, Dr Victor Stevens.
"If we all lost just nine pounds, like the majority of people in this study did, our nation would see vast decreases in hypertension, high cholesterol, diabetes, heart disease and stroke," he added.
In an earlier study, Stevens found that even a 5 pound (2.3 kilos) loss of weight was enough to reduce the risk of developing high blood pressure by 20 per cent.
The Weight Management Initiative from Kaiser Permanente's Care Management Institute has been recommending food journals as part of weight loss maintenance since 2002. The Initiative brings together clinicians, researchers, insurers, and policymakers to work out effective and practical, non-surgical ways to prevent and treat overweight and obesity.
Dr Keith Bachman, a member of the Weight Management Initiative, said that the food diary doesn't have to be a formal thing:
"Just the act of scribbling down what you eat on a Post-It note, sending yourself e-mails tallying each meal, or sending yourself a text message will suffice."
He said the value was the fact that writing it down makes you reflect on what you are eating, which makes us more aware of our habits and gives us a better chance that we will change our behaviour.
"Every day I hear patients say they can't lose weight," said Bachman, but "this study shows that most people can lose weight if they have the right tools and support".
"And food journaling in conjunction with a weight management program or class is the ideal combination of tools and support," he added.
"Weight Loss During the Intensive Intervention Phase of the Weight-Loss Maintenance Trial."
Jack F. Hollis, Christina M. Gullion, Victor J. Stevens, Phillip J. Brantley, Lawrence J. Appel, Jamy D. Ard, Catherine M. Champagne, Arlene Dalcin, Thomas P. Erlinger, Kristine Funk, Daniel Laferriere, Pao-Hwa Lin, Catherine M. Loria, Carmen Samuel-Hodge, William M. Vollmer, Laura P. Svetkey and Weight Loss Maintenance Trial Research Group.
American Journal of Preventive Medicine Volume 35, Issue 2, Pages 118-126 (August 2008)
Click here for American Journal of Preventive Medicine
Source: Journal abstract, Kaiser Permanente.