Abstract
Introduction
Few longitudinal studies have investigated autonomous and controlled forms of eating behaviour regulation and speed of eating in relation to weight outcomes in nationwide samples. Also, with the rising prevalence of obesity and an increased emphasis on weight gain prevention, it is important to understand the effectiveness of women’s weight control strategies. In New Zealand, this is the first longitudinal study of weight control strategies and psychological/behavioural factors that may influence weight gain among adult women.
Objectives:
To examine:
1. How autonomous and controlled forms of eating behaviour regulation, with specific food and eating habits as hypothesised mediators, were related to three-year weight stability*.
2. The association between baseline speed of eating and subsequent weight change* over three years.
3. Baseline demographic and behavioural associations with three-year speed of eating.
4. The prevalence and effectiveness (in terms of three-year weight change*) of women’s weight control strategies.
Methods
A sample of 1601 New Zealand women aged 40-50 years, randomly selected from the nationwide electoral rolls, was recruited in 2009 to participate in a prospective study. At baseline, participants completed self-administered questionnaires on weight control methods, eating behaviour regulation, speed of eating and other behavioural measures. Demographic information, height and weight were collected at all time points.
Results
1. Following mediation analysis, the impact of autonomous regulation on weight stability was reduced by half (adjusted OR 14.3% was attenuated to 7.4%) and was no longer statistically significant (p=0.199). Controlled regulation was not significantly associated with weight stability (p=0.244) prior to mediation analysis.
2. Baseline speed of eating was not significantly associated with three-year weight change (p=0.319) in the adjusted model.
3. For every 10-unit increase in intuitive eating, the adjusted odds of being in a faster speed of eating category at three years decreased by 22.7% (95% CI, 11.0, 32.8). The odds of being in a faster speed of eating group increased by 10.4% (95% CI, 1.7, 19.7) for every 10-unit increase in socioeconomic status as measured by the New Zealand Socioeconomic Index Score (NZSEI). For every 5-unit increase in baseline mindfulness scores, the odds of being in the ‘fast’ compared to the ‘medium’ speed of eating category decreased by 11.0% (95% CI, 4.9, 16.7).
4. Weight control strategies most commonly used were cutting down on meal/snack size (42%) and on fats/sugars (45%), but were not associated with three-year weight loss.
Conclusion
Findings suggest that autonomous regulation indirectly contributes to weight stability through different eating habits with no evidence of a direct effect. Faster eating speeds do not appear to contribute to weight gain among middle-aged women. Three-year speed of eating was determined by various baseline demographic and behavioural factors including intuitive eating, mindful eating, smoking status and socioeconomic status (NZSEI score). Women reported weight control strategies that were largely consistent with public health messages, however these strategies were not associated with three-year weight loss. Causal relationships remain to be examined in intervention studies.