Partner- and planning-based interventions to reduce fat consumption: randomized controlled trial

Compendium of dyadic intervention techniques (DITs) to change health behaviours: a systematic review

BACKGROUND

Dyadic interventions for health behaviour change involving the romantic partner are promising. However, it often remains unclear how exactly the partner is involved in dyadic interventions. We propose a novel compendium of dyadic intervention techniques (DITs) that facilitates systematic description of dyadic interventions in terms of who performs what for whom during intervention delivery and subsequent implementation.

OBJECTIVE

We aimed to systematically characterise dyadic interventions along their degree of partner involvement and to provide a comprehensive list of DITs used in dyadic interventions with romantic partners.

METHODS

We systematically reviewed dyadic health behaviour change interventions with controlled designs. We included 165 studies describing 122 distinct dyadic interventions with romantic partners. Interventions were classified along their degree of partner involvement, 160 DITs were extracted, and their frequencies of use counted.

RESULTS

The majority of interventions (n = 90, 74%) explicitly instructed partners to interact. Half of the DITs were performed jointly by the couple and also targeted the couple. Mostly, couples were instructed to jointly practice communication skills and to jointly perform problem solving for the couple.

DISCUSSION

The present review contributes to the development of a shared and systematic way of describing dyadic interventions to facilitate cumulation of evidence.

Insights into effects of individual, dyadic, and collaborative planning interventions on automatic, conscious, and social process variables

OBJECTIVE

Going beyond the effects of individual planning ("I-for-me"), we investigate the associations of dyadic ("we-for-me") and collaborative ("we-for-us") planning with automatic, conscious, and social process variables that may elucidate the differences through which these three types of planning operate. We tested the effects of three planning interventions on: (1) habit strength, representing an automatic process, (2) the use of individual planning, representing a conscious process, (3) the use of collaborative planning, representing conscious and social processes, and (4) collaborative social control, representing a social process.

METHODS

N = 320 adults were randomly assigned to one of four conditions: (1) the active control condition, (2) the individual planning condition, (3) the dyadic planning condition, or (4) the collaborative planning condition. Self-reported data on habit strength, the use of individual planning, the use of collaborative planning, and collaborative social control were assessed at baseline and at the 9-week follow-up. Analyses used linear mixed modelling.

RESULTS

Compared to the control group, participants in the individual planning condition had stronger habits at the 9-week follow-up. Those in the dyadic planning condition reported higher levels of the use of collaborative planning and higher levels of collaborative social control at the follow-up. Finally, compared to those assigned to the control group, participants in the collaborative planning condition reported stronger habits, higher levels of the use of both individual and collaborative planning, and higher levels of collaborative social control at the follow-up.

CONCLUSIONS

Individual, dyadic, and collaborative planning interventions may result in distinct patterns of changes in the variables representing automatic, conscious, and social processes. In particular, changes in automatic, conscious and social process variables, evoked by the collaborative "we-for-us" planning intervention may reflect the major regulatory effort of forming joint plans and subsequently integrating regular joint exercise into the weekly schedule.

Association between perceived partner support and lifestyle in mother-father dyads expecting a first child

Background

A healthy lifestyle during pregnancy is important for the health of mother and child. However, unfavorable physical activity (PA) and dietary changes are observed in pregnant women and their partner. Partner's influence on lifestyle has been reported by expectant women and men. The first aim was to analyze associations between perceived partner support on expectant parents own as well as their partner's moderate-to-vigorous intensity PA (MVPA) levels and dietary intake. Secondly, this study aimed to investigate intra-couple associations of MVPA, dietary intake and perceived support.

Methods

A total of 152 heterosexual couples were recruited between week 8 and 10 of gestation by means of convenience sampling. Objective anthropometric and 7-day MVPA measurements were performed at 12 weeks of gestation. An online questionnaire was used to assess dietary intake, perceived partner support and socio-demographic characteristics. An Actor-Partner Interdependence Model for distinguishable dyads was constructed to examine the relationship between perceived partner support and both own's (i.e., actor-effect) and the partner's (i.e., partner-effect) MVPA levels, intake of fruits and vegetables, and an "avoidance food group."

Results

For pregnant women, perceived support from their partner was significantly associated with women's own MVPA levels (i.e., actor-effect; estimate = 0.344, SE = 0.168, p = 0.040) as well as the MVPA levels of the men (i.e., partner-effect; estimate = 0.717, SE = 0.255, p = 0.005). No significant actor- nor partner-effects were found for the expectant fathers. For none of the sexes significant actor-effects were found for fruit/vegetables and "avoidance food group" intake. For pregnant women, there was a positive partner-effect for fruit and vegetable intake (estimate = 7.822, SE = 1.842, p < 0.001) and a negative partner-effect for the "avoidance food group" intake (estimate = -16.115, SE = 3.629, p < 0.001). Positive correlations were found for perceived MVPA support (r = 0.40, p < 0.001), MVPA levels (r = 0.24, p = 0.007) and food intake from the "avoidance food group" (r = 0.28, p = 0.005) between partners.

Conclusion

This study shows that male partners can act as significant facilitators for women. Partners may be an important target when promoting MVPA during pregnancy. Additionally, supportive couples seem to strengthen each other in keeping a healthy lifestyle in early pregnancy. These results justify couple-based interventions in the promotion of a healthy lifestyle during the transition to parenthood.

Clinical trial registration

Clinicaltrials.gov, identifier: NCT03454958.

Community-Based Interventions to Reduce Fat Intake in Healthy Populations: A Systematic Review and Meta-Analysis

Background:

Reducing fat intake is a major focus of most dietary recommendations aiming to prevent chronic diseases. Thus, this study aimed to summarize community-based interventions for reducing fat consumption among healthy people.

Methods:

According to PRISMA guidelines, in this systematic review and meta-analysis databases including PubMed/MEDLINE, Scopus, EMBASE, Cochrane Library, Web of Science, ProQuest, and Google Scholar were searched up to January 2021. Randomized clinical trials (RCTs) or quasi-experimental studies reporting the effect of community-based interventions to reduce fat intake in a healthy populations were included. The quality of studies was assessed using the Cochrane Collaboration tool and The Joanna Briggs Institute Critical Appraisal Checklist. Meta-analysis was performed using CMA2 software.

Results:

Our search strategy resulted in a total of 1,621 articles, 43 of which were included in the study after screening. Of the 43 included studies, 35 studies reported a significant decrease in fat intake using educational and multiple intervention methods. About 82% of studies using the technology were effective (significant decrease in fat intake) in reducing fat intake. Moreover, studies specifically designed to change fat intake were more effective than multicomponent interventions. The meta-analysis of high-quality studies showed that the differences in total fat (-0.262 g/d) and saturated fat (-0.350 g/d) intake between the intervention and control groups were statistically significant (P<0.05).

Conclusion:

Based on the high-quality studies, educational and multiple interventions are suggested in the community settings to decrease fat intake. For a concise conclusions, long-term and high frequency interventions focusing on reducing fat intake are desirable.

Can individual, dyadic, or collaborative planning reduce sedentary behavior? A randomized controlled trial

RATIONALE

Although effects of individual planning interventions on physical activity (PA) are well established, less is known about the relationships between planning and sedentary behavior (SB).

OBJECTIVE

This study evaluated the efficacy of individual planning, dyadic planning (i.e., joint planning, targeting the behavior of one person only: the target person), and collaborative planning (i.e., joint planning and joint behavioral performance) on sedentary behavior among dyads.

METHODS

Dyads (N = 320 target persons and their partners, aged 18-90 years) were randomized into three PA planning conditions (individual, dyadic, or collaborative) or an active (education) control condition. Main outcomes, i.e., sedentary time, proportion of time spent in SB and light-intensity PA, proportion of time spent in SB and total PA were measured with GT3X-BT accelerometers at baseline, 1-week follow-up, and 36-week follow-up. Two-level models with measurement points nested in participants were fit, separately for target persons and partners.

RESULTS

Findings for target persons obtained at 1-week follow-up indicated that in the collaborative planning condition SB time significantly decreased, compared to the control condition (p = .013). There was an improvement in the proportion of time spent in SB and light-intensity PA (p = .019), and the proportion of time spent in SB and total PA (p = .018), indicating that SB time was displaced by PA. Effects of individual and dyadic planning were not significant, compared to the control condition. None of interventions had a significant effect on SB indices at 36-week follow-up. Regarding dyadic partners, there were no effects of planning interventions at 1-week follow-up or 36-week follow-up, compared to the control condition.

CONCLUSIONS

Collaborative planning may prompt a short-term reduction of SB time and result in a shift towards a healthier balance between SB time and PA time among target persons, who did not adhere to PA guidelines at baseline.

Postnatal Exercise Partners Study (PEEPS): a pilot randomized trial of a dyadic physical activity intervention for postpartum mothers and a significant other

Background: Research suggests dyadic interventions can increase physical activity; such interventions are untested within postpartum parent couples. Methods: A three-armed pilot randomized trial addressed this gap and tested which type of dyadic intervention is most effective. Inactive postpartum mothers and a significant other were recruited in Australia (n = 143 assessed for eligibility) and randomised in a single-blinded fashion (i.e. participants were blinded) to 1 of 3 dyadic conditions involving a single face-to-face session with access to web-based group support: a minimal treatment control (n = 34), collaborative planning group (n = 38), or collaborative planning + need supportive communication group (n = 30). Participants were asked to wear their accelerometers for 8 days and completed self-report measures at baseline, end of intervention (week 4), and follow-up (week 12). We expected dyads in the collaborative planning + need supportive communication group would have the greatest increases in Physical Activity (PA), autonomous motivation, and partners' need supportive behaviours; and decreases in controlled motivation and controlling partner behaviours. Results: Results from 51 dyads using Bayesian actor-partner interdependence models provided some evidence for a small positive effect on total PA at follow-up for postpartum mothers in the collaborative planning group and for partners in the collaborative planning + need supportive communication group. Furthermore, partners in the collaborative planning + need supportive communication group were more likely to engage in some vigorous PA. At follow-up, postpartum mothers in the collaborative planning + need supportive communication group scored lower on personal autonomous reasons. Conclusions: The impact of prior specification mean intervention effects need to be interpreted with caution. Progression to a full trial is warranted.

Immediate effects of a very brief planning intervention on fruit and vegetable consumption: A randomized controlled trial

Action planning interventions can effectively promote fruit and vegetable (FV) consumption, but not much is known about the day-to-day translation of intervention planning into action. In this randomized controlled trial, immediate intervention effects of a very brief planning intervention on FV consumption during the following 13 days were investigated. After a 13-day pre-intervention diary, N = 206 participants (aged 19-66 years) were randomly allocated to a waiting-list control condition or a planning condition, where they formed one FV plan. Participants from both conditions completed a 13-day post-intervention diary. Self-reported daily FV consumption, FV-specific self-efficacy, and action control were assessed. Segmented linear mixed models estimating a discrete change (i.e. "jump") between diary phases showed a positive "jump" of FV intake and self-efficacy in the planning condition when compared to the control condition. For action control, such effects were not observed. Changes in study variables throughout the post-intervention phase did not differ between both conditions. Present findings extend previous evidence on action planning interventions by showing that increases in self-regulatory (i.e. self-efficacy) and behavioral (i.e. FV intake) outcomes can occur very rapidly and already on the first day for which behavioral increases were planned.

Sun Safe Partners Online: Pilot Randomized Controlled Clinical Trial

Background

Harnessing supportive influences in close relationships is an innovative and potentially effective strategy to improve sun protection behaviors.

Objective

This pilot randomized controlled clinical trial evaluates the feasibility and impact of Sun Safe Partners Online, a web-based, couples-focused intervention to improve sun protection behavior.

Methods

A total of 75 couples reporting suboptimal levels of sun protection recruited from Facebook advertisements were randomized to receive a web-based intervention called Sun Safe Partners Online or a Generic Online Sun Safety Information intervention. Sun Safe Partners Online had 4 individual-focused modules and 4 couples-focused modules. Feasibility was assessed by study enrollment, engagement, follow-up survey completion, and intervention evaluation. Participants completed baseline and a 1-month postintervention survey assessing sun protection and exposure, along with individual and relationship attitudes about the importance of sun protection.

Results

Using Facebook as a recruitment strategy resulted in rapid enrollment and higher acceptance than for the prior telephone and print trial. The follow-up survey completion was higher in the Generic Online condition (100%) than in the Sun Safe Partners Online condition (87.2%). Engagement in Sun Safe Partners Online was high, with more than two-thirds of participants completing all modules. Evaluations of Sun Safe Partners Online content and features as well as ease of navigation were excellent. Sun Safe Partners Online showed small effects on sun protection behaviors and sun exposure on weekends compared with the Generic Online intervention and moderate effect size increases in the Sun Safe Partners Online condition.

Conclusions

This study uses a novel approach to facilitate engagement in sun protection by harnessing the influence of relationships among spouses and cohabiting partners. A couples-focused intervention may hold promise as a means to improve sun protection behaviors beyond interventions focused solely on individuals by leveraging the concern, collaboration, and support among intimate partners and addressing relationship-based barriers to sun protection.

Trial Registration

ClinicalTrials.gov NCT04549675; https://clinicaltrials.gov/ct2/show/NCT04549675

A cluster randomized controlled trial comparing the effectiveness of an individual planning intervention with collaborative planning in adolescent friendship dyads to enhance physical activity (TWOgether)

BACKGROUND

Most adolescents do not meet the recommendations for physical activity (PA) of at least 1 h per day. Individual planning (IP) interventions, including forming plans for when, where and how (action planning) to engage in a behavior, as well as the planning for how to deal with arising barriers (coping planning), are effective to enhance PA in adults. Collaborative planning (CP) is conjoint planning of two individuals regarding a behavior which is performed together. It is assumed that CP stimulates social exchange processes between the planning partners. However, it remains unclear whether planning interventions of PA in adolescents are successful and which planning intervention is more effective. Thus, this cluster randomized controlled trial (RCT) examines changes in daily moderate-to-vigorous PA in adolescents' friendship dyads resulting from planning. Individual self-regulating mechanism and social exchange processes are proposed as mediating mechanisms of the effects of planning for health behavior change.

METHODS

A single-blind four-arm parallel-group cluster-RCT is used. The sample consists of 400 friendship dyads between 14 and 18 years of age. As the recruitment takes place in schools, a cluster randomization of the schools is used to enroll dyads to (a) an IP intervention, (b) a CP intervention or (c) one of the two no-planning control conditions. Devise-measured and self-reported PA as the primary outcomes, self-regulatory strategies, and social exchange processes as secondary outcomes are assessed at three or four time points. After baseline measurement, the baseline ecological momentary assessment of the main variables takes place for 8 days followed by the intervention and a 7-days diary phase. Follow-ups are 1 month and 6 months later. Subsequent to the six-month follow-up, another 7-days diary phase takes place.

DISCUSSION

This is the first study examining IP in comparison to CP in adolescents applying a single-blind cluster RCT. Consequently, the study allows for understanding the efficacy of individual and collaborative planning and the underlying mechanisms in adolescent dyads.

TRIAL REGISTRATION

This RCT was funded by the Swiss National Science Foundation (100019_169781/1) and was registered on 18/06/2018 at ClinicalTrials.gov : NCT03575559 .

Using Smartphone-Based Support Groups to Promote Healthy Eating in Daily Life: A Randomised Trial

BACKGROUND

Although many people intend to eat healthily, they often fail to do so. We report the first randomised trial testing whether smartphone-based support groups can enhance healthy eating.

METHODS

Adults (N = 203) were randomised to the support or control condition (information), and to one of two eating goals (increasing fruit and vegetable/decreasing unhealthy snack consumption). After baseline, participants received information on their assigned eating goal, and completed a 13-day electronic diary. During Days 4-10, support participants were asked to support each other in achieving their eating goal in smartphone-based groups. The primary outcome was daily servings of fruit/vegetables or unhealthy snacks. Maintenance of intervention effects was assessed on Days 11-13, and at 1-month and 2-month follow-ups.

RESULTS

Support participants showed a gradual increase in healthy eating over time, and ate 1.4 fruits and vegetables more, 95% CI [0.3, 2.6], or 0.8 unhealthy snacks less, 95% CI [-1.4, -0.2] than controls on Day 10. Most effects were not maintained at follow-ups.

CONCLUSIONS

Smartphone-based groups can promote fruit and vegetable consumption and decrease unhealthy snack intake. This study extends previous findings of the benefits of support groups, and sheds light on the temporal dynamics of behavior change.

Predictors of dyadic planning: Perspectives of prostate cancer survivors and their partners

OBJECTIVES

Extending individual planning of health behaviour change to the level of the dyad, dyadic planning refers to a target person and a planning partner jointly planning the target person's health behaviour change. To date, predictors of dyadic planning have not been systematically investigated. Integrating cognitive predictors of individual planning with four established predictor domains of social support provision, we propose a framework of predictors of dyadic planning. Including target persons' and partners' perspectives, we examine these predictor domains in the context of prostate cancer patients' rehabilitative pelvic floor exercise (PFE) following radical prostatectomy.

DESIGN

Longitudinal data from 175 patients and their partners were analysed in a study with four post-surgery assessments across 6 months.

METHODS

PFE-related dyadic planning was assessed from both partners together with indicators from four predictor domains: context, target person, partner, and relationship factors. Individual planning and social support served as covariates.

RESULTS

Findings from two-level models nesting repeated assessments in individuals showed that context (patients' incontinence), target person (i.e., positive affect and self-efficacy), and relationship factors (i.e., relationship satisfaction) were uniquely associated with dyadic planning, whereas partner factors (i.e., positive and negative affects) were not. Factors predicting patients' and partners' accounts of dyadic planning differed.

CONCLUSIONS

Resembling prior findings on antecedents of support provision in this context, partner factors did not prevail as unique predictors of dyadic planning, whereas indicators from all other predictor domains did. To establish predictive direction, future work should use lagged predictions with shorter intermeasurement intervals. Statement of contribution What is already known on this subject? Dyadic planning has been shown to be linked to health behaviour change. However, its role in behaviour regulation frameworks is not well investigated, especially regarding factors that might be predictive of dyadic planning. What does this study add? A framework of predictors of dyadic planning in the health behaviour change process is presented. The framework is investigated accounting for both planning partners' perspectives. Context, target person, and relationship factors were related to dyadic planning.

Relationship factors and couples' engagement in sun protection

Individuals may be more motivated to adopt health practices if they consider the benefits of these behaviors for their close relationships. The goal of this study was to examine couple concordance with sun protection and use the interdependence and communal coping theory to evaluate the role of relationship factors in sun protection. One hundred and eighty-four married couples aged 50 years and older completed measures of objective skin cancer risk, perceived risk, sun protection benefits, relationship-centered motivations for sun protection, discussions about sun protection, and sun protection. A mediational model was evaluated. Results indicated a high level of couple concordance. Partners who adopted a relationship-centered motivation for sun protection were more likely to discuss sun protection with one another, and partners who discussed sun protection together were more likely to engage in sun protection. One partner's attitude about personal risk and sun protection benefits was associated with the other partner's sun protection. Wives had higher relationship-centered motivation and discussed sun protection more with their husbands. Behavioral interventions may benefit from encouraging couples to discuss sun protection and encouraging married individuals to consider the benefits of sun protection for their relationship and for their spouse's health.

Action control in dyads: A randomized controlled trial to promote physical activity in everyday life

RATIONALE

Engaging in regular physical activity requires substantial self-regulatory effort such as action control (e.g., continuously monitoring and evaluating an ongoing behavior with regard to one's standards).

OBJECTIVE

The present study examined the effectiveness of an ecological momentary action control intervention for promoting daily physical activity. Also, we tested whether a dyadic compared to an individual intervention displayed an additional benefit.

METHODS

121 overweight and obese individuals and their partners were randomly allocated to an intervention (n = 60; information + action control text messages) or a control group (n = 61; information only). The intervention was delivered in a dyadic vs. individual version of action control. Allocation ratio was 1:1:2 for the dyadic, individual, and control groups, respectively. Daily physical activity was assessed with triaxial accelerometers during a 14-day intervention phase and a 14-day follow-up phase.

RESULTS

Participants in the intervention group showed a higher probability (36.5%) to achieve the recommended daily activity levels (≥30 min of moderate-to-vigorous physical activity per day performed in bouts of at least 10 min) during the intervention and follow-up phase compared to those in the control group (23.0%). The intervention and control group did not differ in terms of daily moderate-to-vigorous physical activity (40.7 vs. 38.6 min per day, p = 0.623).

CONCLUSION

Interventions facilitating action control via text messages seem to be an effective tool for increasing adherence to physical activity guidelines in everyday life. The comparable effects for the dyadic and individual intervention suggest that automated text messages may be just as effective as personalized messages from the romantic partner. Further investigation is needed to examine the usefulness of a dyadic conceptualizing of action control. (controlled-trials.com ISRCTN15705531).

Relationship factors in skin self-examination among couples

OBJECTIVE

Individuals may be more motivated to adopt health-promoting practices if they consider the benefits of these behaviours for their close relationships. The goal of this study was to use the interdependence theory to evaluate the role of relationship factors in skin self-examination (SSE).

DESIGN

The study adopted a cross-sectional survey design.

METHODS

One hundred and eighty-four married couples aged 50 years and older completed measures of skin cancer worry, SSE benefits, SSE barriers, relationship-centred motivations for SSE, discussions about SSE, and SSE practices in the past year.

RESULTS

Couples who discussed SSE with one another were more likely to engage in it. Couples who adopted a relationship-centred motivation for SSE were more likely to discuss SSE, and, ultimately, engage in SSE. One partner's beliefs were associated with the other partner's SSE. Women who adopted a relationship-centred motivation for SSE had husbands who discussed SSE more and also had husbands who were more likely to conduct SSE. Men who adopted a relationship-centred motivation for SSE did not have wives who reported that they discussed SSE more with their husbands and/or wives who were more likely to conduct SSE. These findings suggest that wives' relationship beliefs and discussions with their husbands may have a stronger association with their husbands' SSE practices than the associations between husbands' relationship beliefs and discussions with their wives' SSE practices.

CONCLUSIONS

Behavioural interventions may benefit from encouraging couples to discuss SSE and consider the benefits of SSE for their relationship and for their spouse's health. Statement of contribution What is already known on this subject? Previous studies have shown that people are more motivated to adopt health-promoting behaviours if they consider the benefits of such behaviours for their close relationships. However, little is known about the role of the marital relationship in the engagement in skin self-examination (SSE) practices. What does this study add? This study builds on prior research evaluating the role of relationship factors in cancer screening and surveillance practices. Couples who discuss SSE with one another are more likely to engage in it. Couples who consider the benefits of engaging in SSE for their relationship are more likely to discuss skin examinations and engage in them.

Acceptability and feasibility of self-help Cognitive Remediation Therapy for anorexia nervosa delivered in collaboration with carers: a qualitative preliminary evaluation study

Anorexia nervosa (AN) is an eating disorder without a recommended first-line treatment. Cognitive Remediation Therapy (CRT) is showing great promise in helping patients reduce cognitive inflexibility and excessive detail focus, thinking styles that could make engaging in psychological therapies difficult. CRT has shown to be effective, feasible and acceptable in both individual and group formats, and positive qualitative data has been gathered from both service users and clinicians. The aim of the current study was to assess the use of CRT as a self-help treatment for individuals with AN delivered in collaboration with carers. Six families underwent a six-week self-help CRT intervention. Feedback was gathered from qualitative interviews and analysed using thematic analysis. Neuropsychological outcomes were also collected. Participant feedback regarding the intervention was generally positive, with participants describing a number of benefits such as it creating a space for families to spend time together outside of the eating disorder, acting as a 'gateway' for more emotional work and helping participants to gain insight into their cognitive profiles. These preliminary findings suggest that self-help CRT delivered in collaboration with carers is an acceptable form of treatment, and adds to the growing literature supporting CRT for AN.

A Dyadic Action Control Trial in Overweight and Obese Couples (DYACTIC)

Background

Enhancing physical activity in overweight and obese individuals is an important means to promote health in this target population. The Health Action Process Approach (HAPA), which was the theoretical framework of this study, focuses on individual self-regulation variables for successful health behavior change. One key self-regulation variable of this model is action control with its three subfacets awareness of intentions, self-monitoring and regulatory effort. The social context of individuals, however, is usually neglected in common health behavior change theories. In order to integrate social influences into the HAPA, this randomized controlled trial investigated the effectiveness of a dyadic conceptualization of action control for promoting physical activity.

Methods/Design

This protocol describes the design of a single-blind randomized controlled trial, which comprises four experimental groups: a dyadic action control group, an individual action control group and two control groups. Participants of this study are overweight or obese, heterosexual adult couples who intend to increase their physical activity. Blocking as means of a gender-balanced randomization is used to allocate couples to conditions and partners to either being the target person of the intervention or to the partner condition. The ecological momentary intervention takes place in the first 14 days after baseline assessment and is followed by another 14 days diary phase without intervention. Follow-ups are one month and six months later. Subsequent to the six-months follow-up another 14 days diary phase takes place.

The main outcome measures are self-reported and accelerometer-assessed physical activity. Secondary outcome measures are Body Mass Index (BMI), aerobic fitness and habitual physical activity.

Discussion

This is the first study examining a dyadic action control intervention in comparison to an individual action control condition and two control groups applying a single-blind randomized control trial. Challenges with running couples studies as well as advantages and disadvantages of certain design-related decisions are discussed. This RCT was funded by the Swiss National Science Foundation (PP00P1_133632/1) and was registered on 27/04/2012 at http://www.isrctn.com/ISRCTN15705531.

Electronic supplementary material

The online version of this article (doi:10.1186/1471-2458-14-1321) contains supplementary material, which is available to authorized users.