Research involving nearly 60,000 Japanese people showed a link between eating slower or faster, and losing or gaining weight.
"Changes in eating speed can affect changes in obesity, BMI and waist circumference," a research duo from Japan's Kyushu University wrote in the journal BMJ Open.
"Interventions aimed at reducing eating speed may be effective in preventing obesity and lowering the associated health risks."
BMI stands for Body Mass Index, a ratio of weight-to-height used to determine whether a person falls within a healthy range.
The WHO considers someone with a BMI of 25 overweight, and 30 or higher obese.
In line with recommendations by the Japanese Society for the Study of Obesity, however, a BMI of 25 was taken as obese for Japanese populations for the purposes of the study.
The researchers analysed health insurance data from 59,717 individuals diagnosed with Type 2 diabetes -- a form of the disease that generally hits in adulthood as a result of being overweight.
The participants had regular check-ups from 2008 to 2013.
Data captured included their age and gender, BMI, waist circumference, blood pressure, eating habits, alcohol consumption, and tobacco use.
From the outset, the slow-eating group of 4,192 had a smaller average waist circumference, a mean BMI of 22.3, and fewer obese individuals -- 21.5 percent of the total.