Middle-aged women who motivate themselves to eat healthily have a lower body mass index than those who do so in order to keep others happy, new University of Otago research suggests.
The Department of Human Nutrition study of 1600 women aged between 40 and 50 is the first nationwide research of its kind.
The participants were asked to rate the degree to which different motivations for eating healthily applied to them. They were also surveyed on their specific food and eating habits.
Study co-author Dr Caroline Horwath said that more self-determined and autonomous reasons for eating healthily included enjoying creating healthy meals or viewing eating healthily as integral to one's lifestyle or values.
More "controlled" motivation, on the other hand, involved reasons such as being nagged to eat healthily or feeling expected to do so.
Dr Horwath said the results clearly showed that the more self-determined or autonomous a woman's style of motivation for eating healthily, the lower her body mass index (BMI).
"We found that every 10-unit increase in women's scores for autonomous motivation to eat healthily was associated with a 1.4kg lower body weight, which was equivalent to a 2 per cent lower BMI in a woman of average BMI in this sample."
The results suggest that even a modest decrease in controlled motivation could equate to nearly 1kg lower weight, she says.
"As women in this age bracket are known to be at high risk of weight gain, this amount of weight loss could be important in reducing their risk of diabetes and cardiovascular disease," she said.
The research appears in the September issue of the Journal of the Academy of Nutrition and Dietetics.