The researchers say measuring and charting our weight daily makes us see the link between what we eat and our weight.
However, for reasons they could not explain, the researchers found this method seems to work better for men than for women.
"You just need a bathroom scale and an excel spreadsheet or even a piece of graph paper," explains senior author David Levitsky, a professor of nutrition and psychology at Cornell University, Ithaca, NY.
He says this forces you to be aware of the link between your weight and what you eat, and notes that this goes against what we used to be told:
"It used to be taught that you shouldn't weigh yourself daily, and this is just the reverse."
In the 2-year study, participants who lost weight in the first year were able to keep it off through the second year. The result is significant because many studies show that around 40% of weight lost through dieting is often put back on within a year, and within 5 years, all of it is regained.
For their study, Prof. Levitsky and first author Carly Pacanowski, a nutritional sciences PhD candidate, randomly assigned 162 overweight men and women to an intervention group and a control group.
All participants attended an initial educational session where they learned about evidence-based strategies for weight loss, including specific approaches based on choosing one's own weight loss method - with an emphasis on making small changes.
The small changes suggested included skipping dessert a few times per week, using a meal replacement for lunch three times a week and avoiding snacks between meals most of the time.
Members of the control group then left the session, which went on to give the intervention group instructions and equipment for daily self-monitoring.
They were given a typical bathroom scale and asked to weigh themselves at the same time every day - preferably first thing in the morning - and record the result on a website chart set up by the researchers.
Self-monitoring men more successful than women at losing weight
The intervention group were then given a target of losing 1% of their weight, in any manner they chose. This is roughly the equivalent of consuming around 150 calories a day less than usual for around 2 weeks.
Once the participants had maintained their 1% weight loss for 10 days, they were asked to lose another 1%. This pattern continued with a long-term goal of losing 10% of their starting body weight in the first year.
Prof. Levitsky says each participant devised his or her own way of losing weight - some reduced portion size, others stopped snacking, and some skipped meals.
After the first year, the control group was then given bathroom scales and briefed on self-monitoring, as the intervention group had been at the start of the first year.
During the second year, the intervention group were asked to just monitor their weight every day by stepping on the scales and plotting the result on the website chart. On average, the intervention group members measured and plotted their weight four times a week.
Even though weight loss is modest, self-monitoring seems to be effective
The results in the first year showed that on average, the intervention group lost more weight than the controls (2.6 kg versus 0.5 kg). The researchers also found that men were significantly more successful than women at losing weight in the first year, and keeping it off in the second year.
Commenting on the findings, Prof. Levitsky says the self-monitoring approach "seems to work better for men than women, for reasons we cannot figure out yet."
The authors suggest that by stepping on a scale and seeing the results tracked on a chart every day acts as a reinforcer of behavior that helps reduce weight and keep it off - such as eating less, and taking exercise. Prof. Levitsky adds:
"We think the scale also acts as a priming mechanism, making you conscious of food and enabling you to make choices that are consistent with your weight."
The authors conclude that even though the intervention group on average only managed to lose 2% of their starting weight and keep it off over the 2-year period, it is enough to show that self-weighing and visual feedback could be a useful weight management strategy, combined with other techniques.
They note that as little as 5% weight loss has been shown to be clinically significant in overweight people.
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