a1 S. Daniel Abraham International Center for Health and Nutrition, Department of Epidemiology and Health Systems Evaluation, Ben-Gurion University of the Negev, P.O. Box 653, Be’er-Sheva 84105, Israel
a2 Nuclear Research Center Negev, Dimona, Israel
a3 Brigham and Women’s Hospital and Harvard Medical School, and the Departments of Epidemiology and Nutrition, Harvard School of Public Health, Boston, MA, USA
Objective We examined the halo effect of a 2-year weight-loss diet trial, the Dietary Intervention Randomized Controlled Trial (DIRECT), on the weight and nutritional patterns of participants' spouses.
Design DIRECT participants in a research centre workplace were randomly assigned to one of three diets: Low-fat, Mediterranean or Low-carbohydrate. A sample of wives of the DIRECT participants, who attended support update meetings specific to their husband's diet during the first 6 months, were followed for 2 years.
Setting South Israel.
Subjects Seventy-four women (mean age = 51 years, mean BMI =26·6 kg/m2).
Results Among the wives of husbands randomised to the Low-fat, Mediterranean and Low-carbohydrate diet, self-reported weight change was respectively −1·48 kg, −2·30 kg and −4·62 kg after 6 months, and +0·39 kg, −3·00 kg and −2·30 kg after 2 years. Weight loss among wives whose husbands were in the alternative diet groups combined (Mediterranean+Low-carbohydrate) was significantly greater than among wives whose husbands were in the Low-fat group after 6 months (P = 0·031) and 2 years (P = 0·034). Overweight wives experienced more weight loss. The weight change of couples was significantly correlated (r = 0·42, P < 0·001). Across all dietary groups, wives had significant improvement in their dietary patterns in all food groups according to their husbands' diets, mainly by a larger significant decrease in carbohydrate consumption in the Low-carbohydrate group (P = 0·013 compared to Low-fat). Six-month weight change among the seventy-four DIRECT participants whose wives took part in the group support sessions was −5·2 kg, compared to −3·5 kg among the 248 DIRECT participants whose wives did not take part in these sessions (P = 0·020).
Conclusions Focusing on the couple as a unit could provide a cost-effective approach to weight-loss programmes.
(Received November 13 2008)
(Accepted July 22 2009)
(Online publication August 26 2009)