The major finding of this study is that changes in eating speed can affect obesity, BMI and waist circumference. The control of eating speed may therefore be a possible means of regulating body weight and preventing obesity, which in turn reduces the risk of developing non-communicable diseases. Eating quickly is associated with impaired glucose tolerance and insulin resistance,18 19 and is a known risk factor for diabetes through increases in body weight.20 Other studies have also reported associations between eating quickly and increased BMI, indicating that eating speed is a contributing factor for obesity.7 8 21–26 A possible reason for this association is that fast eaters may continue to eat until they feel full despite having already consumed an adequate amount of calories, and the combined effect of eating quickly and overeating may contribute to weight gain.27 In contrast, eating slowly may help to increase feelings of satiety before an excessive amount of food is ingested.28–30 A prospective study of schoolgirls found that the reduction of eating speed was able to suppress weight gain and prevent obesity.31 The findings of these studies are consistent with those of our analysis.
In addition to BMI-based definitions of obesity, waist circumference-based definitions of abdominal obesity have also become increasingly important in recent years. Cerhan et al proposed that assessments of waist circumference should accompany assessments of BMI.32 As a supplementary analysis, we employed a fixed-effects model to examine the effects of changes in eating speed on waist circumference in our subjects. The results showed that when compared with fast eaters, normal-speed eaters and slow eaters had reductions in waist circumference of 0.21 cm and 0.41 cm, respectively (P<0.001). These results support our findings of the effects of changes in eating speed on obesity.
Our results also indicated that frequently eating dinner within 2 hours before sleeping, snacking after dinner and skipping breakfast contribute to the development of obesity. Previous studies have identified eating after dinner and within 2 hours before sleeping as risk factors of metabolic syndrome.7 This supports our findings that the cessation of these habits can help to reduce obesity and BMI. Skipping breakfast has also been shown to be associated with excess weight and obesity, and is a risk factor of metabolic syndrome.7 9 33 Our generalised estimating equation model revealed that consistently eating breakfast can reduce obesity, which also corroborates the findings of previous studies. However, our fixed-effects model showed that consistently eating breakfast did not affect changes in BMI. It has been reported that skipping breakfast over a long period is associated with high BMI and elevated cardiometabolic risks.34 Consistently eating breakfast may therefore help to control obesity and BMI.