The main finding from this study was that children’s rate of eating at 4 years of age, specifically, mouthfuls of food/min at a single laboratory test meal, predicted overweight status at age 6 years and excess weight gain from ages 4 to 6 years. In multiple regression analyses, the effect of child mouthfuls/min was independent of maternal BMI that, as expected, predicted changes in child body fat indexes. These findings indicate the importance of rapid eating rate in the development of childhood obesity, consistent with several prior studies. Drabman et al.
) reported that a rapid eating style was associated with adiposity in children. Obese boys (18
) and girls (19
) ate twice as rapidly as nonobese control subjects in other reports. Eleven-year-old obese children ate much more rapidly than nonobese children and, unlike nonobese children, their eating rate did not decelerate during the course of the meal (33
). This lack of deceleration of eating rate suggests an inadequate satiety signal or inadequate response to that signal.
A rapid eating style in infancy also has been found to be a marker for excess weight gain (7
). In the IGS cohort, nutritive sucking rate at 3 months of age was significantly greater among HR than LR children, and increased sucking rate predicted increased weight gain up to 24 months of age (7
). In a separate prospective cohort study of infants, rapid sucking rate predicted excess weight gain up to age 6 years (21
). In a recent UK-based study, child eating rate was found to be highly heritable and positively associated with child overweight status (20
). In conjunction with the present findings, these results implicate rapid eating rate as a behavioral precursor to obesity in childhood. Additional prospective studies using larger samples are needed to confirm this causal pathway, as opposed to rapid eating being a correlate or consequence of rapid weight gain.
When comparing children who actually became overweight or obese at age 6 years, 32% of HR children had a BMI ≥85th percentile compared with only 3.4% of LR children. Thus, in this subsample of the IGS families who participated in the video-recorded meals at age 4 years, the effect of risk group on overweight status was strong, which is consistent with our previous report (4
). What is noteworthy from the present study was the differences in the preceding eating rate and energy intake at 4 years of age. Overweight and obese children at age 6 had 3.12 (1.17) mouthfuls/min compared with 2.24 (0.95) for those who were of normal weight. Similarly, in measures of total calories consumed/min, overweight and obese children consumed 16.58 (6.36) kcal/min compared with the normal-weight child who consumed 12.22 (5.05) kcal/min. Thus, the child’s eating more vigorously in just one test meal and maternal BMI predicted increased weight gain (increased in BMI) over a 2-year period. Similarly, childhood mouthfuls/min during the test meal predicted body fat at age 6.
Curiously, despite the prospective effect of child eating rate on child anthropometric measures, there was no significant effect of risk group on eating rate measures at year 4. Thus, a primary hypothesis was not supported. Although this may reflect a “true” null finding, inspection of means in suggests that the means were in the expected directions and could not attain significance given our sample size. Specifically, there was a trend for mouthfuls of food/min (2.16 vs. 2.60, P = 0.10) and kcal/min (11.9 vs. 13.9, P = 0.18) to be greater among HR than LR children. A larger sample size may have provided the power for these mean differences to achieve significance.
To explore this further, a post hoc power analysis was conducted based on the data in . This analysis estimated the number of children per risk group that would have been needed in this study, and may be necessary in future investigations, to detect significant risk group differences in eating rate and parental prompts. Assuming a two-tailed significance test and α = 0.05, the number of youth per risk group needed to attain significance with 80% power would be 86 (mouthfuls/min), 116 (kcal/min), 235 (discouragements/ min), and 323 (encouragements/min). Thus, the lack of support for our primary hypotheses may have been due, in part, to low power.
Another main finding from the present study was the significant intercorrelations among child feeding behaviors and parental prompts to eat during the test meal. Parental prompts to eat was associated with increased total energy intake/min at the test meal (r
= 0.48), increased child requests for food (r
= 0.55), and a shorter child meal duration (r
= −0.67). Similar findings were reported by Drucker et al.
), who found that greater parental encouragements to eat, discouragements to eat, and total prompts were associated with increased total energy intake by young children at a laboratory buffet meal. In a study of 4–8-year-old children whose home meals with parents were directly observed, greater parental prompts to eat were associated with increased food ingestion by children (35
). In yet another report, Klesges et al.
) found that total parental food prompts during meals was associated with increased child eating time. These studies suggest that a more appetitive or vigorous eating style by children is associated with greater feeding prompts by parents during the meal, although cause and effect cannot be determined. Future research should address this question.
It is noteworthy that parental eating prompts, despite being associated with child eating rate, and food requests and refusals, was not a risk factor for child overweight at age 6 years or excess weight gain from 4 to 6 years in the present study. It may be the case that child mouthfuls/min and calories eaten/min are stronger determinants of future weight status than feeding prompts by parents. It may also be the case that parental prompts are secondary to the child eating traits with which they are associated. For example, parental restriction of child eating is elicited by child overeating and parental perceptions that their child is overweight (37
). Indeed, maternal restrictive feeding at child age 5 years predicted excess child BMI at age 7 years in the IGS cohort, but only among HR children (6
). Future studies need to identify parental feeding behaviors that have a casual influence on the development of childhood obesity.
Girls showed greater accretions in fat mass compared to boys in the present study, consistent with other reports in the literature (38
). Future analyses of this cohort will need to continue to model sex effects in analyses. Controlling for sex, however, the effect of child eating rate was significant in the regression analyses, suggesting that the effect was not simply due to potential sex differences in eating styles that may have impacted on results.
A noteworthy finding in our study was that children’s total meal energy intake/min was negatively correlated with active mealtime (i.e., a shorter duration) and positively associated with total daily energy intake from the 3-day food records. Thus, children eating faster during the test meal consumed more calories as recorded from the 3-day food records kept by parents. Interestingly, these children also spontaneously requested more food during the test meal.
The present findings should be interpreted in light of study strengths and limitations. Strengths include use of a prospective cohort design, investigation of children born with and without a familial predisposition to obesity, and precise measurement of child eating and parental feeding behaviors that were evaluated under controlled laboratory conditions. Limitations include a relatively smaller sample size and investigation of a single ethnic group. In addition, physical activity was not measured at year 4 and therefore was not included as a predictor variable. Total energy expenditure was not examined in the present study, although, in prior analyses of this cohort, HR and LR children did not differ in total energy expenditure (5
). Finally, behavioral measures at year 6, such as food intake outside of the home and physical activity, were not obtained.
In summary, the vigorous feeding style among overweight children described in this study includes more rapid eating (i.e., mouthfuls/min) and greater food consumption (i.e., kcal/min). This eating style may be a behavioral phenotype for a genetically based predisposition for the development of obesity. Future studies are needed to understand the potential genetic and physiological factors, such as hormonal or neuro-biological factors, associated with this vigorous feeding style in young children at HR for obesity. Rapid eating could relate to the construct of food reward (40
). From a clinical viewpoint, future intervention research should address strategies for targeting a vigorous eating style in obese prone children. Possibilities include the promotion of less energy-dense foods as a target for vigorous eating (41
), satiety training procedures (42
), or teaching a slowing eating rate to help minimize excessive weight gain. The development of clinically effective protocols to assist parents of children at risk for obesity with their eating behavior is also needed.