Halo effect of a weight-loss trial on spouses: The DIRECT-Spouse study
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. 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. South Israel. Seventy-four women (mean age = 51 years, mean BMI =26.6 kg/m2). 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). Focusing on the couple as a unit could provide a cost-effective approach to weight-loss programmes.
Public Health Nutrition: 13(4), 544–549 doi:10.1017/S1368980009991273
Halo effect of a weight-loss trial on spouses: the DIRECT-Spouse
, Dan Schwarzfuchs
, Meir J Stampfer
and Iris Shai
*; for the
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:
Research Center Negev, Dimona, Israel:
Brigham and Women’s Hospital and Har vard Medical School,
and the Departments of Epidemiology and Nutrition, Harvard School of Public Health, Boston, MA, USA
Submitted 13 November 2008: Accepted 22 July 2009: First published online 26 August 2009
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 5 51 years, mean BMI 526?6 kg/m
Results: Among the wives of husbands randomised to the Low-fat, Mediterranean
and Low-carbohydrate diet, self-reported weight change was respectively
21?48 kg, 22?30 kg and 24?62 kg after 6 months, and 10?39 kg, 23?00 kg and
22?30 kg after 2 years. Weight loss among wives whose husbands were in the
alternative diet groups combined (Mediterranean1Low-carbohydrate) was sig-
niﬁcantly greater than among wives whose husbands were in the Low-fat group
after 6 months (P 5 0?031) and 2 years (P 5 0?034). Overweight wives experi-
enced more weight loss. The weight change of couples was signiﬁcantly corre-
lated (r 5 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 con-
sumption in the Low-carbohydrate group (P 5 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 25?2 kg, compared to 23?5kg
among the 248 DIRECT participants whose wives did not take part in these
sessions (P 5 0?020).
Conclusions: Focusing on the couple as a unit could provide a cost-effective
approach to weight-loss programmes.
Health promotion for couples includes the opportunity
to use the partner’s support in encouraging healthy
behaviours such as a balanced diet, weight control and
. Moreover, a dietary intervention
programme may exert a beneﬁcial effect on the partici-
. Family environment also appears to
signiﬁcantly affect compliance
. As eating patterns are
likely to be similar across family members
ence and maintenance of certain eating patterns might be
associated with the level of household support for healthy
. A combined worksite and family intervention
is more successful in changing nutritional patterns than
worksite intervention alone
. This strategy might be
a promising approach for long-term success in weight-
loss programmes. However, few studies have explored
the mutual effect of speciﬁc diet strategies on spouses.
In the 2-year Dietary Intervention Randomised Con-
trolled Trial (DIRECT)
among 322 participants, with
dropout rates of 5 % after 1 year and 15 % after 2 years, we
showed that the Low-carbohydrate and Mediterranean
diets are effective alternatives to the Low-fat diet in
terms of weight loss, achieving more favourable effects
on lipids in the Low-carbohydrate diet and on glycaemic
control in the Mediterranean diet. Here we describe a
*Corresponding author: Email firstname.lastname@example.org r The Authors 2009
parallel study describing the 2-year effect of dietary
intervention on weight and nutritional patterns of the
spouses of the DIRECT participants across the three
dietary arms. We further examined the association
between a programme of spouse support, provided
through periodic group meetings, and the success of the
DIRECT participants in losing weight.
The DIRECT and DIRECT-Spouse study population
The DIRECT was conducted between July 2005 and June
2007 in a research centre workplace in the south of Israel.
Participants (86 % of whom were men) were randomly
assigned to one of three diets. The Low-fat diet
30 % of energy from fat, 10 % of energy from saturated fat
and 300 mg cholesterol a day, with a total energy intake of
6276 kJ/d (1500 kcal/d) for women and 7531.2 kJ/d (1800
kcal/d) for men. The Mediterranean diet
aimed for 35 % of
energy from fat, mainly from olive oil and nuts, and energy
intake restricted to 6276 kJ/d (1500 kcal/d) for women and
7531.2 kJ/d (1800 kcal/d) for men. The Low-carbohydrate
aimed for 20 g of carbohydrate daily for the induc-
tion phase (2 months), gradually reaching a speciﬁc target
carbohydrate level that could maintain the weight loss. Total
calories, protein and fat intake were not limited, although
participants were counselled to prefer vegetarian sources
andtoavoidtrans fat. The DIRECT-Spouse sub-study
included wives of participants in the DIRECT, who share the
same household but who were not part of the DIRECT
themselves. The DIRECT-Spouse study was approved by the
ethical committee of Soroka Medical Center.
Recruitment and follow-up of the study
We invited the wives of participants in the DIRECT, and
explained the theme and purpose of the sub-study. Those
who agreed to participate ﬁlled out at baseline (August
2005) a baseline questionnaire that was sent to them
personally, and included various demographic and life-
style characteristics as well as questions regarding their
predictions regarding the dieters’ success in the DIRECT.
Wives were asked to also report their current weight.
Every 2 months during the ﬁrst 6 months of the
DIRECT, participating spouses were invited to a 90 min
support group meeting led by a clinical dietitian speciﬁc
to the DIRECT participant’s dietary arm. The curriculum
of these meetings was similar in all groups and included
various topics regarding the principles of the DIRECT
intervention, learning about healthy nutrition and ways
for leading a healthy lifestyle. The aim of the meetings
was not to directly treat the spouses, but to update them
about the principles of the diet strategy to which their
husbands were randomised and to equip the spouses
with materials that may enable the wives to support their
husbands in their diet. The women were followed for
changes of weight, diet and monthly expenses for food
at 6 and 24 months.
One-way ANOVA and x
tests were used to evaluate the
demographic and lifestyle characteristics of the study
population. We used non-parametric tests (Wilcoxon Signed
test) to assess the weight changes within each dietary sub-
group and non-parametric tests (Mann–Whitney test) to
evaluate the differences between each group and the
reference group (Low-fat diet). We evaluated weight chan-
ges of overweight spouses (n 40; BMI $ 25 kg/m
line) and compared weight loss across the diet groups using
non-parametric tests (Mann–Whitney test). We further
evaluated the correlation between weight changes of the
DIRECT participants and their wives during the ﬁrst
6 months, across the three dietary arms. In the DIRECT, we
identiﬁed the ﬁrst 6 months as the ‘maximal weight-loss
phase’ and the 7–24 month period as the ‘maintenance’
. To evaluate the impact of the spouse support
group meetings, we compared the weight change of parti-
cipants whose wives took part in the sub-study with that of
DIRECT participants whose spouses did not take part in the
study. The wives completed a food-changes questionnaire
6 months after baseline; we modiﬁed the 127-item
Israeli FFQ, developed
in our Nutri-
tional Center, to assess the changes of each food item
among the wives, within the ﬁrst 6 months of the DIRECT.
In the FCQ, the spouses were asked whether their own
consumption of each speciﬁc food item had changed
(options: increased/did not change/decreased) since the
beginning of the DIRECT. An increase in consumption of a
speciﬁc food item was scored 11; a decrease in consump-
tion of a speciﬁc food item was scored 21; no difference in
consumption was scored 0. The scores were summed in
each food group and divided by the number of items in
the group; the results were used in the data analysis. All
statistical analyses were performed with the use of SPSS
statistical software, version 13 (SPSS Inc., Chicago, IL,
USA). P value ,0?05 was considered signiﬁcant.
Out of the 322 participants of the DIRECT, 90?5% were
married. Of the 113 wives who completed baseline ques-
tionnaires (38?8 % of spouses), seventy-four took part
in support group meetings during the ﬁrst 6 months of
the DIRECT (n 28, 24 and 22 for the corresponding Low-
fat, Mediterranean and Low-carbohydrate DIRECT partici-
pants’ diets). At baseline, their mean age was 50?79 years,
and mean BMI was 26?6(
SD 4?72) kg/m
. The characteristics
of the wives across the randomised assigned dietary arm
of the DIRECT participants are described in Table 1.
Characteristics were similar across groups. There were no
Weight-loss trial effect on spouses 545
signiﬁcant differences between the baseline weights of the
wives across the three dietary arms (P 5 0?33). Furthermore,
no signiﬁcant differences in demographic characteristics,
initial weight and weight loss after 6 months were found
between wives who completed the 2-year follow-up and
wives who did not (data not shown).
After 6 months, the spouses of the DIRECT participants
lost a mean of 2?64 kg (P 5 0?002 compared to baseline).
Weight loss (Fig. 1a) was 1?48 (
SD 2?72) kg for wives of
DIRECT participants randomised to the Low-fat diet, 2?30
SD 2?39) kg for the Mediterranean and 4?62 (SD 6?56) kg
for the Low-carbohydrate diet (P , 0?05 for all groups,
compared to baseline).
We compared the results of the alternative diets
(Mediterranean and Low-carbohydrate) to the traditional
diet (Low-fat). Weight loss among wives whose husbands
were in the Mediterranean diet group (P 5 0?064) and
the Low-carbohydrate diet group (P 5 0?058) tended to
be greater, compared to the Low-fat diet-group. Overall,
there was signiﬁcantly greater weight loss among the
spouses of the husbands in the two alternative diet-
groups combined (Mediterranean 1 Low-carbohydrate),
compared to the traditional Low-fat diet (P 5 0?031).
Wives’ BMI decreased signiﬁcantly after 6 months
(DBMI 5 0?80 (
SD 1?91) kg/m
; P 5 0?001 compared to
baseline), with DBMI of 0?46 (SD 1?03), 0?62 (SD 1?06) and
SD 3?16) kg/m
for wives of participants randomised
to the Low-fat, Mediterranean and Low-carbohydrate
groups, respectively (P 5 0?013, 0?024 and 0?059,
respectively, compared to baseline).
Overall weight loss at 6 months among the overweight
spouses (n 40) with BMI $ 25 kg/m
at baseline (mean
BMI 5 29?5(
SD 4?04) kg/m
) was 3?54 kg (SD 5?14)
(P , 0?05 compared to baseline). For the corresponding
Low-fat, Mediterranean and Low-carbohydrate dietary
arms, weight loss of overweight spouses was 1?75 (
3?19), 2?96 (SD 2?58) and 5?36 (SD 7?45) kg, respectively
(P 5 0?068 (n 12), P 5 0?08 (n 14) and P 5 0?042 (n 14),
respectively, compared to baseline).
A signiﬁcant correlation (Fig. 1b) was found between
weight changes of the seventy-four DIRECT participants
and their wives during the ﬁrst 6 months of the inter-
vention (r 5 0?42; P , 0?001). The strongest and only
statistically signiﬁcant correlation was for the Low-
carbohydrate diet group (r 5 0?57; P 5 0?005).
The 6-month weight changes among the seventy-four
DIRECT participants whose wives took part in the group
sessions was 25?15 kg, compared to the 23?54 kg among
the 248 DIRECT participants whose spouses did not take
part in these sessions (P 5 0?020).
We analysed the changes in the wives’ diets (Fig. 2). In all
three groups the wives reported lower consumption of
saturated fat and trans fat, meat and poultry, bread and
pastry, grains, pasta and potato, fruit, sweets and swee-
tened beverages. In all three groups the wives reported an
increased consumption of ﬁsh and vegetables. There was a
signiﬁcantly larger decrease in the consumption of grains,
pasta and potatoes among wives whose husbands were on
the Low-carbohydrate diet, compared to the Low-fat diet
(P 5 0?013). Similar trends were reported at 24 months.
After 2 years, weight changes among ﬁfty-three wives
were 10?39 (
SD 3?71) kg among wives of husbands in the
Low-fat group (n 24; P 5 0?453, compared to baseline),
SD 6?21) kg among wives of husbands in the Med-
iterranean group (n 14; P , 0?05, compared to baseline)
and 22?30 (
SD 2?39) kg among wives of husbands in
Table 1 Baseline characteristics of the wives of the DIRECT participants (n 74)
Low-fat (n 28) Mediterranean (n 24) Low-carbohydrate (n 22) Entire group (n 74)
SD Mean SD Mean SD Mean SD P(v)*
Age (years) 50?56?052?05?57 49?46?97 50?76 6?09 0?645
Weight (kg) 67?810?51 73?115?92 73?18 14?07 70?93 13?53 0?329
)24?93?69 27?81 4?98 27?79 5?14 26?66 4?72 0?074
%% % %
Primary school – – – –
High school 50?054?552?452?20?952
Never or past 77?875?095?281?9
Currently 1–5 cigarettes/d 14?88?34?89?7
Currently 6–20 cigarettes/d 7?412?5–4?20?152
Currently more than 20 cigarettes/d – 4?2–4?2
1–2 times a week 29?620?823?825?00?174
3–4 times a week 18?520?814
.4 times a week 14?8– 4?86?9
DIRECT, Dietary Intervention Randomized Controlled Trial.
*Kruskal–Wallis test for the continuous variables and x
for the categorical variables.
-Physical activity 5 at least 30 min of vigorous activity a day.
546 R Golan et al.
Low-carbohydrate group (n 15; P , 0?05, compared to
baseline). Overall, the signiﬁcantly greater weight loss
among spouses of participants in the two alternative diet
groups combined (Mediterranean 1 Low-carbohydrate),
compared to the traditional Low-fat diet, remained after
2 years (P 5 0?034). For DIRECT participants randomised
to the Low-fat, Mediterranean and Low-carbohydrate diets,
adherence rates at 2 years were 85?7%, 58?4 % and 68?2%
(P , 0?05 between groups). However, spouse populations
baseline characteristics such as weight, education, origin,
smoking and physical activity patterns.
The baseline questionnaire included a question
‘Regarding the possibility of your husband succeeding
and maintaining his diet throughout the DIRECT’ (scale
from 1 – don’t agree to 5 – fully agree). An afﬁrmative
answer was a signiﬁcant predictor for the DIRECT parti-
cipant’s success in losing weight during the ﬁrst 6 months
of the intervention (b 5 0?24; P 5 0?046).
In the follow-up questionnaires, wives were asked
whether their household expenses for food products
increased, did not change, or decreased as a result of their
husbands’ diet. The proportions of wives who reported
an increase in monthly food expenses were 25?9 % for
Low-fat, 26?1 % for Mediterranean and 14?3 % for Low-
carbohydrate (P 5 0?68). The rest reported no change.
We evaluated the effect of the DIRECT study on weight
loss and nutritional patterns of wives of participants. We
found that wives were indirectly affected by the inter-
vention trial of their husbands, by losing weight and
improving their nutritional patterns. Overweight spouses
at baseline experienced more weight loss. The results
suggest that a dietary intervention delivered to one family
member may have a beneﬁcial effect on the spouse,
and may present a possible ripple effect that may occur
as a result of minimal involvement in a weight-loss
programme targeting one’s spouse. This may provide
additional justiﬁcation for health promotion and dietary
modiﬁcation programmes to target couples as the unit for
intervention, as a shared activity.
Our study has several limitations. First, the weight and
height of the spouses were self-reported and not directly
measured, as was done with DIRECT participants;
although this may introduce a possible bias, other studies
have previously validated self-reported weights
Second, the assignment of the spouses study was not
randomised and was based on the willingness of the wife
to participate. It is possible that these wives were more
supportive of their husband’s weight-loss efforts than
spouses who were unwilling to attend group meetings
themselves or complete assessments, likely introducing a
self-selection bias. Third, we followed wives only, due to
the small proportion of women participating in the
DIRECT. The inﬂuence of a dietary intervention on
spouses of both sexes should be further investigated.
Strengths of our study include the long duration of follow-
up, the comparison of the three diet strategies and the
close connection our clinical dietitian had with the wives,
enabling close follow-up.
Low-carbohydrate diets without energy restriction have
earlier been shown to be at least as effective as low-fat,
high-carbohydrate diets in inducing weight loss, and were
Spouse weight loss
–30 –20 –10 0 10
DIRECT participant weight loss
Low-fat Mediterranean Low-carbohydrate
Fig. 1 Weight changes in the Dietary Intervention Randomized
Controlled Trial (DIRECT). (a) Changes in weight of wives of
participants after 6 months, by randomised dietary arm. Values
are means, with an
SE of 1 from the mean indicated by error bars.
*n 74, P , 0?05 within diet group, Wilcoxon Signed Ranks Test,
as compared to time 0; **P , 0?06 in the Mediterranean or Low-
carbohydrate diet group, as compared to the traditional diet Low-
fat diet group. (b) Correlation between weight changes among
DIRECT participants and their wives after 6 months: (
fat diet group (n 27, r 5 0?418, P 5 0?842);
drate diet group (n 22, r 5 0?566, P 5 0?005);
nean diet group (n 23, r 5 0?322, P 5 0?16)
Weight-loss trial effect on spouses 547
more favourable in overall metabolic outcomes
The strongest correlation between the weight loss of the
DIRECT participants and the weight loss of their spouses
was found in those randomised to the Low-carbohydrate
diet. The changes in nutritional patterns were in accord
with the principles of the three diet strategies of the
, and present the possible
ripple effect of the trial on the spouses who reported
changing their own eating habits. The DIRECT study
found that the Mediterranean and Low-carbohydrate diets
may be effective strategies in losing weight and maintain-
ing weight loss. Moreover, it was suggested that these
diets might be used as speciﬁc prescriptions for certain
metabolic targets. The ﬁndings among the wives suggest
that these two alternative diets may also be adapted by
spouses as well as the traditional diet and, therefore, may
be considered as suitable effective alternative strategies
for couples that undertake a joint diet.
DIRECT participants whose spouses took part in the
support group meetings lost signiﬁcantly more weight
than the DIRECT participants whose spouses did not
participate. Although the present study was not randomised
and therefore one may argue that it is hard to use these
data to conclude the beneﬁt of involving the spouse in
order to raise the participants’ success in a dietary inter-
vention, these data are consistent with earlier studies that
found that a family intervention was more successful in
changing eating patterns than worksite intervention
. Moreover, we found that a wife believing in
her husband’s ability to succeed in his weight-loss project
was a signiﬁcant predictor for the dieter losing weight
during the ﬁrst 6 months of the intervention. These
ﬁndings suggest a positive relationship between the
involvement of the spouse in the intervention and success
in weight loss; such ﬁndings are consistent with earlier
data which recognised social and family support as fac-
tors that may raise adherence and encourage health
behaviour change in high-risk individuals
and a recent
study reporting the signiﬁcant role played by the spouse
in encouraging the dieter in succeeding in his diet
Our results suggest an approach of designing dietary
intervention programmes that focus on the workplace as
well as on the household.
The present study was funded by the following sources:
(i) Nuclear Research Center Negev (NRCN); (ii) The
Dr. Robert C. and Veronica Atkins Research Foundation;
(iii) The S. Daniel Abraham International Center for
Health and Nutrition, Ben-Gurion University, Israel. The
ﬁrst two funding sources were not involved in any stage
of the design, conduct or analysis of the study, and
987 65 432 1
Total change score
Type of food group
Fig. 2 Changes in nutritional patterns after 6 months among wives (n 74) of participants in the Dietary Intervention Randomized
Controlled Trial (DIRECT), by randomised dietary arm:
, Low-fat (n 28); , Mediterranean (n 24); , Low-carbohydrate (n 22).
Food groups: 1 5 eggs and dairy, 2 5 saturated fat and trans fat, 3 5 meat and poultry, 4 5 ﬁsh, 5 5 bread and pastry, 6 5 grains,
pasta and potato, 7 5 fruit, 8 5 vegetables, 9 5 sweets and sweet beverages. The score was calculated for each food item as
follows: ‘Increased’ 511, ‘Decreased’ 521, ‘No change’ 5 0. The score for each food group is the sum of all food items in the
speciﬁc group divided into the number of food items in the food group according to the food change questionnaire, then divided
according to the ‘n’ of each dietary arm, so each score represents the percentage of change.
Values for two diet groups within
a row with unlike superscript letters were signiﬁcantly different (P , 0?05)
548 R Golan et al.
had no access to the study results before publication.
The authorship responsibilities were as follows: study
design and performance – R.G., D.S., M.J.S. and I.S.; data
analysis – R.G.; paper drafting – R.G.; paper review – D.S.,
M.J.S. and I.S. None of the authors have relationships
with companies that make products relevant to the
manuscript. The authors are thankful to the 322 DIRECT
participants for their consistent cooperation.
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