The objective of the pilot study (feasibility study) is to assess the acceptability and feasibility of the developed 2EAT dietary treatment in obese older adults (55+).

For ecological reasons, the goal of the dietary treatment plan is to achieve an intake of 60% plant-based proteins in older adults (55+) in a healthy and nutritionally adequate way during a period of weight loss. The investigators developed the new dietary treatment plan for 6 months (RCT). To further optimize the new treatment plan the 2EAT study includes this feasibility study with a duration of 8 weeks.

In the feasibility study, the effect of a more plant-based hypocaloric diet on the protein intake of older adults (55+) with obesity is evaluated. To assess the feasibility of the treatment plan, 20 obese older adults will follow the newly developed dietary treatment for 8 weeks. The participants will be guided by experienced dieticians that are part of the study consortium, in their dietetic practice. All dieticians will be trained to execute the 2EAT dietary treatment plan.

The desired effect of the treatment is that participants change their protein intake and achieve an intake of 1.2 g/kg/d of which 60% is from plant-based sources. Additionally, the experience of both the older adults as well as the experience of the dieticians will be monitored during the 8 weeks of intervention. During 8 weeks there will be continuous monitoring of the implementation of the treatment plan by keeping logbooks (dieticians), and measurement of the food intake of the participants. When participants deviate from the diet, the dietician must make timely adjustments with available behavioral techniques. The primary outcome of the feasibility phase is the protein intake: source (plant-based vs. animal-based), amount (g/kg/day) and protein quality per meal (amino acid score). Secondary outcomes are the body weight and BMI of participants and qualitative information about the experience of participants and dieticians with the use of the new treatment plan. Dieticians are professionals in working with older clients with obesity during a weight loss program, and are competent to execute the treatment plan and additionally monitor and make adjustments to coach the participant towards the desired diet and goal. Findings and experiences from the 8-week feasibility study will be used to further improve the 2EAT dietary treatment. The optimized dietary plan will eventually be used in the RCT study.

Inclusion Criteria:

• Aged 55 or older
• Are obese: have a BMI of >30 kg/m2 or BMI >27 kg/m2 and waist circumference >88 cm (women) or >102 cm (men)
• Living independently (not in a health facility)
• The willingness that the general practitioner will be notified of study participation
• Written informed consent
• Willingness to comply with the protocol
• Consent of the study physician

Exclusion Criteria:

• Inability to understand the Dutch language
• Cognitive impairment (MMSE <15)
• Use of total or partial parenteral nutrition (TPN)
• Alcohol or drug abuse in the opinion of the investigator
• Current enrolment in a fixed rehabilitation program or other intervention studies
• Palliative treatment or a life expectancy of ≤ 3 months
• Following a vegan (100% plant-based) diet
• Active medical treatment interfering with this intervention (e.g. cancer patients receiving systemic and immune therapy)
• Physical disabled: unable to meet the general daily exercise guideline for adults
• Planned a holiday during the intervention period and is unable to attend group- or individual sessions for > 1 week