Hypotheses: Compared to the provision of population-based lifestyle advice, providing DNA-based lifestyle advice via personalized nutrigenomics testing (PNT) to two distinct patient populations (patients attending group counselling sessions at the East Elgin Family Health Team and transplant recipients) in which overweight and obesity are common concerns, will motivate them to adopt healthier dietary and physical activity habits via changes in attitudes and/or subjective norms and/or behavioural control, lead to greater fat loss, increased percent lean mass and therefore improve health and quality of life outcomes for both patient populations. It is also hypothesized that dietary strategies related to the intake of one or more dietary components of interest (protein, monounsaturated fat, polyunsaturated fat, total fat, sodium, carbohydrates, alcohol and calories) will mitigate post-transplant weight gain associated with the following SNPs: ACE (rs4343), FTO (rs1558902) and MC4R (rs571312).

Sample Size: No research to date has studied the aforementioned hypotheses. Previously published data assessing weight loss in a SNI group compared to a PNT group using a randomized clinical intervention model in a different population used a sample of n = 93 and an alpha \< 0.05 to find statistical significance after 3-7 month follow-up. Similarly, nutrigenomics research in the ACE gene (rs4343) found statistical significance using a sample of n = 104 and an alpha \< 0.05. A sample size calculation with 80% power and an alpha of 0.05 indicated that 37 participants per group (n = 148 total) are needed to detect significant differences between groups for changes in body fat percentage (primary outcome). Since it is feasible for this research, a larger sample size goal (n = 400) will be used to increase power and draw meaningful inferences from the data. There will be 100 participants in each patient group (n = 200 in SNI group, n = 200 in PNT group) in this landmark study.

Design and Methods: Participants will be recruited from the Canadian Transplant Association (CTA) meetings with the assistance of the Director, Sandra Holdsworth (transplant recipients; n = 200) and from the Group Lifestyle Balance Program (GLB Program) through the East Elgin Family Health Team (GLB; n = 200) for this randomized clinical intervention trial. Word-of-mouth recruitment is also expected. This trial involves a total of four groups of patients. The two main patient groups include overweight or obese (BMI ≥ 25 kg/m\^2), stable transplant recipients greater than or equal to one year post-transplant, and overweight or obese (BMI ≥ 25 kg/m\^2) patients who are attending the GLB program at the East Elgin Family Health Team. Within these two main patient groups, there will be two sub-groups (n = 100 per sub-group). Patients will be randomized to receive either PNT or standard nutrition intervention (SNI) based on strategies from the standard teaching tool used by dietitians in both patient populations: 'Just the Basics' - developed by the Canadian Diabetes Association for transplant participants. Participants from the East Elgin Family Health Team, will participate in the GLB Program and will either complete the standard program (SNI Group) + receive population-based nutrition and physical activity recommendations or will complete a modified GLB program + receive personalized nutrition and physical activity recommendations based on their genetics (PNT Group). Baseline data will be conducted consisting of a food frequency questionnaire and three-day food records using a validated multiple pass method. Bioelectrical Impedance Analysis (BIA) will be conducted to assess body composition and to derive percent and kg body fat and lean mass. Weight and height will be measured using a weigh scale and stadiometer. Surveys will be completed by participants to assess several demographic characteristics, as well as key components of the Theory of Planned Behaviour. Those patients randomized to the PNT group will be instructed on a tailored nutrition care plan and physical activity goal based on their individual genetic profile. At the same time, the SNI group will be instructed on general nutrition and physical activity recommendations for weight loss. A survey based on the Theory of Planned Behaviour will be administered before and after participants receive their nutrition and physical activity advice. These components are needed so that we can assess whether or not social and built environment factors, subjective norms, attitudes and behavioural control influence change in dietary intake. Monthly email or phone call reminders (depending on participant preference) will be sent to participants as a reminder of their nutrition and physical activity plan for transplant recipients. For East Elgin Family Health Team participants, reminders of the nutrition and physical activity plan will be incorporated into the GLB Program. Three months, six months and twelve months after baseline data collection and individual nutrition interventions, baseline data will be repeated. After the study is complete, participants in the SNI group will be offered a nutrigenomics test and consultation with a registered dietitian.

Statistical Analysis: A paired t-test or repeated measures ANOVA will be used to assess within group change from baseline to each of the follow-up time points for: BMI, body fat, lean mass, water weight, TPB components, dietary intake (protein, total fat, saturated fat, unsaturated fat, carbohydrates, alcohol, calories and sodium), and physical activity. A repeated measures ANOVA will be used to test between group differences from baseline to each of the follow-up time points for: BMI, body fat, lean mass, water weight, TPB components, dietary intake (protein, total fat, saturated fat, unsaturated fat, carbohydrates, alcohol, calories and sodium) and physical activity. If significant mean differences are detected, a Tukey's post hoc test will be used to compare differences by group. Statistical significance will be determined by P \< 0.05. General linear regression models will be used to assess the effect of each genotype of interest (ACE rs4343, MC4R rs573112, FTO rs1558902) and the impact of each dietary component of interest (protein, total fat, saturated fat, unsaturated fat, carbohydrates, alcohol, calories and sodium) on BMI and body composition from baseline to each follow-up time point. We will control for age, sex, ethnicity, immunosuppressive medications (transplant recipients) and baseline body composition and BMI. IBM SPSS Statistics, version 21.0 will be used for the data analysis.