Halo effect of a weight-loss trial on spouses: the DIRECT-Spouse study.
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.


METHODS
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.


METHODS
South Israel.


METHODS
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.
Golan
Rachel
R
S. Daniel Abraham International Center for Health and Nutrition, Department of Epidemiology and Health Systems Evaluation, Ben-Gurion University of the Negev, Be'er-Sheva, Israel.
Schwarzfuchs
Dan
D
Stampfer
Meir J
MJ
Shai
Iris
I
D000328:Adult; D050528:Diet, Carbohydrate-Restricted; D018752:Diet, Fat-Restricted; D038441:Diet, Mediterranean; D004038:Diet, Reducing; D015987:Effect Modifier, Epidemiologic; D005260:Female; D005500:Follow-Up Studies; D015438:Health Behavior; D006801:Humans; D007557:Israel; D008297:Male; D008875:Middle Aged; D009765:Obesity / Q000178:diet therapy*; D018454:Spouses / Q000523:psychology*; D011795:Surveys and Questionnaires; D016896:Treatment Outcome; D015431:Weight Loss; D017132:Workplace