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When it comes to research, in a lot of studies, investigators are forced to collect data based on self-reports. For example, when researchers cannot measure mood or eating habits 24/7, they ask participants to give honest and accurate answers. Since self-reports rely heavily on the participants' memory and honesty, the data collected might not always be reliable. In a new study, researchers set out to find just how accurate self-reporting is in measuring weight for patients who underwent bariatric surgery, also known as weight-loss surgery.

"Obtaining standardized weights in long-term studies can be difficult. Self-reported weights are more easily obtained, but less accurate than those from a calibrated scale and may be inaccurately reported," according to background information in the article.

For this study, the research team headed by Nicholas J. Christian, Ph.D., of the University of Pittsburgh Graduate School of Public Health and his colleagues, compared people's self reports on their weights under two conditions post bariatric surgery and the weights recorded via a scale. The data for the weights were collected between April 2010 and November 2012 as a part of an observational cohort, the Longitudinal Assessment of Bariatric Surgery-2. The cohort involved 2,458 adults who had initial Rou-en-Y gastric bypass, laparoscopic adjustable gastric band or another type of weight loss procedure at 10 centers.

The data was collected via mailed questionnaires that were sent out every year and asked them to report their weight measured at a medical office and the weight that they measured on their own. The two different weight measurements were then compared to the weight that the researchers measured. The researchers stated that at the end, their study included 988 adult participants. 164 of them provided a self-reported weight measured in a medical setting, 580 provided a self-reported and self-measured weight and 244 provided both measurements. The researchers found that for both men and women, self-reported medical weights were very close to the measured weight. For self-reported and self-measured weights, both men and women underestimated their weight by an average of 2.2 pounds or less.

"Small differences between self-reported and measured weights were found and may be due to differences in clothing, inaccurate personal scales, time between measurements, or intentional misrepresentation," the authors wrote. "Self-reported weights after bariatric surgery may be more accurate because participants who undergo surgery to lose weight may be especially attentive to their weight."

The researchers believe that when participants are asked to report what they weighed during a doctor visit, their answers can be quite accurate. The study was published in JAMA.