The HDLS pilot study was a 12-week randomized trial conducted at the University of Hawaii Cancer Center (UHCC) between September 2016 and October 2017 to demonstrate feasibility and efficacy of following the IER+MED diet as an approach to reduce VAT. Extensive details of the intervention are provided in a previous publication (21). Briefly, eligibility included being of East Asian ancestry (Japanese, Chinese or Korean), residing in Honolulu County, BMI between 25 and 40 kg/m2, ages 35 to 55 years, no pregnancy, and no serious health issues. Inclusion criteria included normal blood count and biochemistry profile and whole-body dual-energy x-ray absorptiometry (DXA)-derived VAT at L4-L5 ≥ 90 cm2 for men and ≥ 80 cm2 for women as determined at the eligibility clinic visit.
HDLS included baseline and Week 12 measurements of anthropometry and DXA (21). For the current analysis, outcomes of interest include body weight and VAT. One participant was excluded from analyses as s/he dropped out during the first week of HDLS and, thus, had no self-rated adherence data.
The study protocol [NCT03639350] was approved by the institutional review board at the University of Hawaii at Manoa. Study volunteers provided written informed consent. Figure 1 is a CONSORT diagram and the CONSORT and TIDieR checklists are provided as supplementary material (Additional file 1 and 2, respectively).
Randomization and masking
Once eligibility was confirmed, stratified and blocked randomization was used to allot participants into either the IER+MED (n=30) or DASH (n=30) group, to ensure balance between groups. Randomization strata were defined by sex and high (80 cm2 for women or 90 cm2 for men to <150 cm2) or very high (≥150 cm2) VAT. The assigned diets were labeled as either Diet A or Diet 1 to blind participants, recruitment, and clinic staff to IER+MED or DASH group allocation. Research dietitians, who were responsible for intervention activities, were blinded to participant measures except diet and body weight.
Procedures and outcomes
Dietary and physical activity prescriptions
Diet and physical activity prescriptions in HDLS have been reported previously (21). Briefly, the intervention group was assigned a IER+MED diet, and the active comparator group was assigned a euenergetic DASH diet for 12 weeks. Dietary materials for IER+MED were originally developed and tested for use among white women in the United Kingdom (15) and were modified to include examples of foods and beverages more readily available in Hawaii (21). Both groups were advised to walk one hour daily, five days per week, to reduce confounding due to physical activity. Participants in the IER+MED group were advised to exercise only on their MED days.
During an in-person dietary consultation (~45-60 minutes) participants were provided with a personalized, group-specific, diet booklet (depicting serving sizes within food groups and examples of foods), individualized food lists and menus, and trackers to encourage compliance to prescriptions. Dietitians called participants once a week between Weeks 1 and 4, and at Week 6, 8 and 10, and conducted an in person follow-up at Week 12, to assess participants’ adherence to their intervention plans (22) and provide guidance using motivational interviewing principles (23;24).
Assessment of adherence to prescribed diet and physical activity prescriptions
During follow-up calls conducted by study dietitians and the in-person dietitian consultation at Week 12, all participants were asked: “How well have you been following your diet plan? On a scale of zero to ten with zero being not at all, four being somewhat, and ten being following the plan very well, where would you place yourself?”. Similarly, the same questions were asked for adherence to physical activity prescriptions. Self-rated adherence scores assisted with identifying participant’s barriers to change and setting personal diet and physical activity goals to achieve by the next follow-up call (23;25).
These assessment questions were adapted from those used to assess motivation and confidence to change dietary behaviors used by Resnicow et al. (23;24;26). For example, in the Body & Soul Study, participants were asked “on a scale of 1 to 10 (with 10 being the highest), how motivated or interested are you in increasing your fruit and vegetable consumption?” Resnicow et al. found that this time and cost-effective assessment technique assisted with increasing fruit and vegetable intake among African Americans in a church setting.
Responses to self-rated adherence scores across the 12 week HDLS were averaged for each person, and participants were divided into a high or low level of adherence, split by median score (7.3 for diet and 7.1 for physical activity).
During the clinic visit at Week 12, participants completed a self-administered exit questionnaire. The two questions relevant to this analysis were if he/she would have been interested in cooking classes or demonstrations and whether the materials provided were sufficient to be able to follow the diet plan. Participants recorded their responses using a 5-point Likert scale (strongly agree/agree/neither agree or disagree/disagree/strongly disagree).
At 6-months post-intervention, recruitment staff performed a follow-up, by telephone, of participants who completed the HDLS. Participants were interviewed using a standardized questionnaire tailored to the study objectives. Questions pertinent to this analysis included “What type or types of exercise have you been doing since you completed the study?”; “Are you still trying to follow the diet you were assigned to during the study?”; “If no, can you describe the type of diet that you have been following since you completed the study?”; and “Do you have any comments or suggestions as to how the study could be improved?”.
Analyses were limited to participants with complete Week 1 study data (n=59). Multiple imputation was used to replace missing values of the outcome and exposure variables and generate five imputed datasets. Less than 5% of data values were missing. Mean changes in VAT and weight loss, from baseline to 12 weeks, were computed by self-reported adherence level, overall and by randomization arm, and compared between adherence levels using a t-test. Responses to 5-point Likert scale questions are reported as frequencies and percentages. Quantitative analyses were performed using IBM SPSS Statistics version 26 (IBM Corp., Armonk, NY, USA) and statistical significance was defined as p<0.05.
Qualitative methods were used to evaluate responses to the open-ended 6-month post-intervention telephone interview questions (27). Responses to open-ended questions from each participant were transcribed separately by staff members not involved in the study. Co-investigators (KC, HO) and another staff member independently coded each response transcript. Each coder identified and nominated common themes and preliminary codes, and all codes were reviewed and discussed by the team until a final consensus was reached. A codebook was then developed for analysis using NVIVO Version 11 (QSR International, Melbourne, Australia) and used to drive a subsequent thematic analysis of all interview transcript data (27).