Japanese researchers studied 59,717 people who had been given diagnoses of Type 2 diabetes. At periodic checkups over six years, they collected data on obesity and waist circumference, eating and sleep habits, alcohol consumption, the medications they took and whether they smoked.
The researchers categorized the subjects as fast, normal or slow eaters based on self-reports.
After controlling for other factors, they found that compared with the slow eaters, normal speed eaters were 29 percent more likely, and fast eaters 42 percent more likely, to be obese. Going to sleep within two hours of eating dinner and snacking after dinner were also associated with obesity, but skipping breakfast was not.
The study, in BMJ Open, found an association, not a causal relationship. But the researchers suggest that a possible reason for the association is that fast eaters may continue eating without waiting to realize they have eaten enough, whereas slow eaters may have time to start to feel full and then stop.
The researchers had no data on physical exercise and energy intake, which could have altered the results, and only Japanese men and women were included in the study, so the findings may not be applicable to other populations. Also, the study depended on self-reports, which are not always reliable, the New York Times reported.