Plant-based Protein-rich Weight Loss Intervention in 55+ Adults With Obesity (2EAT)

The objective of the 2EAT RCT is to investigate whether a shift towards more plant-based (≥60% with a minimum of 50%) protein intake can be achieved in an energy restricted diet for three and six months in older adults (55+) with obesity.

The 2EAT researchers developed a new dietary counseling plan for six months. This includes four individual consultations, five group meetings and three 24h-recalls. In these six months, participants receive dietary counseling focused on energy restriction (-500 kcal), higher protein intake (aim towards 1.2 g/kg/d, minimum of 0.8 g/kg/d). Participants are randomly allocated either to the more plant-based diet (≥60%) or the more animal-based diet (≥60%). At the start of the intervention, participants are provided with a workbook and recipe book.

Secondary objectives are to assess the effect after three and six months 2EAT dietary treatment on 1) weight loss and 2) skeletal muscle mass. Exploratory objectives are to assess the effect after three and six months 2EAT dietary treatment on 1) physical health outcomes (muscle mass and physical performance), 2) body composition, 3) metabolic blood parameters, 4) vitality and quality of life, 5) nutritional intake, 6) behavioral changes, 7) evaluate the process of the dietary treatment.

Study Overview

• Status: Recruiting
• Conditions: Obesity
• Intervention / Treatment: Behavioral: More plant-based protein intake during weight loss

• Study Type: Interventional
• Enrollment (Estimated): 200
• Phase: Not Applicable

Contacts and Locations

• Study Contact: Name: Susanne Wildemast; Phone Number: +31623492734; Email: s.wildemast@hva.nl
• Study Contact Backup: Name: Sjors Verlaan; Phone Number: +31657442955; Email: s.verlaan@hva.nl

Study Locations

• Netherlands
  • South Holland
    • Amsterdam, South Holland, Netherlands, 1067SM
      • Recruiting
      • Hogeschool van Amsterdam
      • Contact: Wildemast; Phone Number: 0641679606; Email: s.wildemast@hva.nl

Participation Criteria

Eligibility Criteria

• Ages Eligible for Study: Adult; Older Adult
• Accepts Healthy Volunteers: No

Description

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 vegetarian or vegan (100% plant-based) diet
• Bariatric surgery
• Active medical treatment interfering with this intervention (e.g. weight loss medication as Ozempic, 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 > 3 weeks

The health conditions below will be assessed by the study physician. When a condition interferes the dietary treatment or if the diet worsens the participants health it counts as exclusion criteria:

• Diagnosed with unstable coronary heart disease (CHD), decompensated heart failure, uncontrolled hypertension or uncontrolled arrhythmias (e.g. heart failure NYHA >3)
• Diagnosed degenerative neurocognitive disorders
• Diagnosed with renal failure
• COPD GOLD >3

Study Plan

How is the study designed?

Design Details

• Primary Purpose: Treatment
• Allocation: Randomized
• Interventional Model: Parallel Assignment
• Masking: None (Open Label)

Number of Arms

2

Arms and Interventions

Participant Group / Arm	Intervention / Treatment
Experimental: More plant-based diet; Participants receive dietary counseling for six months focusing on 1) more plant-based protein (≥60%), 2) higher protein intake (aim 1.2 g/kg/d, minimum 0.8 g/kg/d) and 3) energy restriction (-500 kcal).	Behavioral: More plant-based protein intake during weight loss; Participants receive dietary counseling for six months focusing on 1) energy restriction (-500 kcal), 2) higher protein intake (aim 1.2 g/kg/d, minimum 0.8 g/kg/d) and according to their assigned diet, either 3) more plant-based protein (≥60%) or more animal-based protein (≥60%).
Experimental: More animal-based diet; Participants receive dietary counseling for six months focusing on 1) more animal-based protein (≥60%), 2) higher protein intake (aim 1.2 g/kg/d, minimum 0.8 g/kg/d) and 3) energy restriction (-500 kcal).	Behavioral: More plant-based protein intake during weight loss; Participants receive dietary counseling for six months focusing on 1) energy restriction (-500 kcal), 2) higher protein intake (aim 1.2 g/kg/d, minimum 0.8 g/kg/d) and according to their assigned diet, either 3) more plant-based protein (≥60%) or more animal-based protein (≥60%).

What is the study measuring?

Primary Outcome Measures

Outcome Measure	Measure Description	Time Frame
Feasibility of high plant-based protein intake while simultaneously striving for weight loss and increased protein intake	Three-day food record (plant protein intake as part of total protein intake; g/day)	At baseline (week 0), in week 13 (halfway), in week 26 (end), and optional follow-up (week 52)

Secondary Outcome Measures

Outcome Measure	Measure Description	Time Frame
Feasibility of a weight loss diet during a more plant-based, higher protein intake	Three-day food record on energy (kcal/day)	At baseline (week 0), in week 13 (halfway), in week 26 (end), and optional follow-up (week 52)
Feasibility of an increased protein intake during a more plant-based protein, weight loss diet	Three-day food record on protein intake (g/day)	At baseline (week 0), in week 13 (halfway), in week 26 (end), and optional follow-up (week 52)
Effect of 2EAT dietary treatment on weight loss	Body weight in kg (calibrated weighing scales)	At baseline (week 0), in week 13 (halfway), in week 26 (end), and optional follow-up (week 52)
Effect of 2EAT dietary treatment on skeletal muscle mass	Skeletal muscle mass (appendicular lean soft tissue (ALST) in kg) via a DXA-scan	At baseline (week 0), in week 13 (halfway), in week 26 (end), and optional follow-up (week 52)

Other Outcome Measures

Outcome Measure	Measure Description	Time Frame
Effect of 2EAT dietary treatment on physical performance	Short Physical Performance Battery (SPPB). Minimum value: 0; Maximum value 12. Score 0-3: severe limitations; score 4-9: intermediate limitations; score 9-12: normal function.	At baseline (week 0), in week 13 (halfway), in week 26 (end), and optional follow-up (week 52)
Effect of 2EAT dietary treatment on walking distance	400 meter walk test (MWT) in seconds (s)	At baseline (week 0), in week 13 (halfway), in week 26 (end), and optional follow-up (week 52)
Effect of 2EAT dietary treatment on muscle strength	Hand Grip Strength (kg)	At baseline (week 0), in week 13 (halfway), in week 26 (end), and optional follow-up (week 52)
Effect of 2EAT dietary treatment on fat free mass	Fat free mass (in kg) via BODPOD air displacement plethysmograph	At baseline (week 0), in week 13 (halfway), in week 26 (end), and optional follow-up (week 52)
Effect of 2EAT dietary treatment on LDL-cholesterol	Serum LDL-cholesterol (mmol/L)	At baseline (week 0), in week 12 (halfway), in week 26 (end)
Effect of 2EAT dietary treatment on HDL-cholesterol	Serum HDL-cholesterol (mmol/L)	At baseline (week 0), in week 12 (halfway), in week 26 (end)
Effect of 2EAT dietary treatment on total cholesterol	Serum total cholesterol mmol/L)	At baseline (week 0), in week 12 (halfway), in week 26 (end)
Effect of 2EAT dietary treatment on triglycerides	Serum triglycerides (mmol/L)	At baseline (week 0), in week 12 (halfway), in week 26 (end)
Effect of 2EAT dietary treatment on long-term blood glucose concentration	HbA1c (mmol/mol)	At baseline (week 0), in week 12 (halfway), in week 26 (end)
Effect of 2EAT dietary treatment on insulin resistance	Homeostasis Model Assessment of Insulin Resistance (HOMA-IR) (values >2 indicate insulin resistance)	At baseline (week 0), in week 12 (halfway), in week 26 (end)
Effect of 2EAT dietary treatment on inflammation	High sensitivity CRP (mg/L)	At baseline (week 0), in week 12 (halfway), in week 26 (end)
Effect of 2EAT dietary treatment on vitamin B12 levels	Serum vitamin B12 (pg/mL)	At baseline (week 0), in week 12 (halfway), in week 26 (end)
Effect of 2EAT dietary treatment on body iron stores	Serum ferritin (mcg/L)	At baseline (week 0), in week 12 (halfway), in week 26 (end)
Effect of 2EAT dietary treatment on blood haemoglobin concentration	Blood haemoglobin (mmol/L)	At baseline (week 0), in week 12 (halfway), in week 26 (end)
Effect of 2EAT dietary treatment on vitality	De Nederlandse vitaliteitsmeter (VITA-16 questionnaire). Minimum value: 0; Maximum value 7. Higher scores indicate more vitality.	At baseline (week 0), in week 13 (halfway), in week 26 (end), and optional follow-up (week 52)
Effect of 2EAT dietary treatment on quality of life	Short-Form-36 questionnaire (SF-36) Minimum value: 0; Maximum value 100. Higher scores indicate better health-related quality of life. A score of 0 indicates very poor health-related quality of life, whereas a score of 100 indicates a very good health-related quality of life.	At baseline (week 0), in week 13 (halfway), in week 26 (end), and optional follow-up (week 52)
Effect of 2EAT dietary treatment on carbohydrate intake	Three-day food record on carbohydrate (g/day)	At baseline (week 0), in week 13 (halfway), in week 26 (end), and optional follow-up (week 52)
Effect of 2EAT dietary treatment on fat intake	Three-day food record on fat (g/day)	At baseline (week 0), in week 13 (halfway), in week 26 (end), and optional follow-up (week 52)
Effect of 2EAT dietary treatment on saturated fat intake	Three-day food record on saturated fat (g/day)	At baseline (week 0), in week 13 (halfway), in week 26 (end), and optional follow-up (week 52)
Effect of 2EAT dietary treatment on fiber intake	Three-day food record on fiber (g/day)	At baseline (week 0), in week 13 (halfway), in week 26 (end), and optional follow-up (week 52)
Effect of 2EAT dietary treatment on calcium intake	Three-day food record on calcium (mg/day)	At baseline (week 0), in week 13 (halfway), in week 26 (end), and optional follow-up (week 52)
Effect of 2EAT dietary treatment on iron intake	Three-day food record on iron (mg/day)	At baseline (week 0), in week 13 (halfway), in week 26 (end), and optional follow-up (week 52)
Effect of 2EAT dietary treatment on zinc intake	Three-day food record on zinc (mg/day)	At baseline (week 0), in week 13 (halfway), in week 26 (end), and optional follow-up (week 52)
Effect of 2EAT dietary treatment on magnesium intake	Three-day food record on magnesium (mg/day)	At baseline (week 0), in week 13 (halfway), in week 26 (end), and optional follow-up (week 52)
Effect of 2EAT dietary treatment on selenium intake	Three-day food record on selenium (mcg/day)	At baseline (week 0), in week 13 (halfway), in week 26 (end), and optional follow-up (week 52)
Effect of 2EAT dietary treatment on vitamin B1 intake	Three-day food record on vitamin B1 (mg/day)	At baseline (week 0), in week 13 (halfway), in week 26 (end), and optional follow-up (week 52)
Effect of 2EAT dietary treatment on vitamin B2 intake	Three-day food record on vitamin B2 (mg/day)	At baseline (week 0), in week 13 (halfway), in week 26 (end), and optional follow-up (week 52)
Effect of 2EAT dietary treatment on vitamin B6 intake	Three-day food record on vitamin B6 (mcg/day)	At baseline (week 0), in week 13 (halfway), in week 26 (end), and optional follow-up (week 52)
Effect of 2EAT dietary treatment on folic acid intake	Three-day food record on folic acid (mcg/day)	At baseline (week 0), in week 13 (halfway), in week 26 (end), and optional follow-up (week 52)
Effect of 2EAT dietary treatment on vitamin B12 intake	Three-day food record on vitamin B12 (mcg/day)	At baseline (week 0), in week 13 (halfway), in week 26 (end), and optional follow-up (week 52)
Effect of 2EAT dietary treatment on vitamin C intake	Three-day food record on vitamin C (mg/day)	At baseline (week 0), in week 13 (halfway), in week 26 (end), and optional follow-up (week 52)
Effect of 2EAT dietary treatment on vitamin D intake	Three-day food record on vitamin D (mcg/day)	At baseline (week 0), in week 13 (halfway), in week 26 (end), and optional follow-up (week 52)
Effect of 2EAT dietary treatment on vitamin E intake	Three-day food record on vitamin E (mg/day)	At baseline (week 0), in week 13 (halfway), in week 26 (end), and optional follow-up (week 52)
Effect of 2EAT dietary treatment on behavior, dimension "diffuse emotions"	Nederlandse Vragenlijst Eetgedrag (NVE) questionnaire on dimension "diffuse emotions". Sum questions 3, 8, 10, 28 and divide by 4. Minimal score: 0; maximal score: 5. A score of 5 means the individual has a lot of diffuse emotions, a score of 0 means no diffuse emotions.	At baseline (week 0), in week 13 (halfway), in week 26 (end), and optional follow-up (week 52)
Effect of 2EAT dietary treatment on behavior, dimension "clearly described emotions"	Nederlandse Vragenlijst Eetgedrag (NVE) questionnaire on dimension "clearly described emotions". Sum questions 1, 5, 13, 16, 20, 23, 25, 30, 32 and divide by 9. Minimal score: 0; maximal score: 5. A score of 5 means the individual has clearly described emotions, a score of 0 means no clearly described emotions.	At baseline (week 0), in week 13 (halfway), in week 26 (end), and optional follow-up (week 52)
Effect of 2EAT dietary treatment on behavior, dimension "emotional eating"	Nederlandse Vragenlijst Eetgedrag (NVE) questionnaire dimension "emotional eating". Sum questions 1, 3, 5, 8, 10, 13, 16, 20, 23, 25, 28, 30, 32 and divide by 13. Minimal score: 0; maximal score: 5. A score of 5 means the individual is a very emotional eater, a score of 0 means no emotional eating.	At baseline (week 0), in week 13 (halfway), in week 26 (end), and optional follow-up (week 52)
Effect of 2EAT dietary treatment on behavior, dimension "external eating"	Nederlandse Vragenlijst Eetgedrag (NVE) questionnaire dimension "external eating". Sum questions 2, 6, 9, 12, 15, 18, 21, 24, 27, 33 and divide by 10. Minimal score: 0; maximal score: 5. A score of 5 means the individual is a very external eater, a score of 0 means no external eating.	At baseline (week 0), in week 13 (halfway), in week 26 (end), and optional follow-up (week 52)
Effect of 2EAT dietary treatment on behavior, dimension "diet-oriented eating"	Nederlandse Vragenlijst Eetgedrag (NVE) questionnaire dimension "diet-oriented eating". Sum questions 4, 7, 11, 14, 17, 19, 22, 26, 29, 31 and divide by 10. Minimal score: 0; maximal score: 5. A score of 5 means the individual is a very diet-oriented eater, a score of 0 means no diet-oriented eating.	At baseline (week 0), in week 13 (halfway), in week 26 (end), and optional follow-up (week 52)
Process evaluation of the 2EAT dietary treatment	Paper-based questionnaire with open questions	At week 26 (end)
End evaluation of the 2EAT dietary treatment	Paper-based questionnaire with open questions	Optional follow-up (week 52)

Collaborators and Investigators

• Sponsor: Amsterdam University of Applied Sciences
• Investigators: Principal Investigator: Peter Weijs, Amsterdam University of Applied Sciences

Study record dates

Study Major Dates

• Study Start (Actual): August 13, 2024
• Primary Completion (Estimated): October 1, 2026
• Study Completion (Estimated): April 1, 2027

Study Registration Dates

• First Submitted: December 8, 2025
• First Submitted That Met QC Criteria: February 17, 2026
• First Posted (Actual): February 24, 2026

Study Record Updates

• Last Update Posted (Actual): February 24, 2026
• Last Update Submitted That Met QC Criteria: February 17, 2026
• Last Verified: December 1, 2025

More Information

Terms related to this study

• Keywords: Obesity; Ageing
• Additional Relevant MeSH Terms: Nutrition Disorders; Overnutrition; Body Weight; Overweight; Pathological Conditions, Signs and Symptoms; Nutritional and Metabolic Diseases; Signs and Symptoms; Obesity
• Other Study ID Numbers: RAAK.PRO04.033 - RCT

Plan for Individual participant data (IPD)

• Plan to Share Individual Participant Data (IPD)?: UNDECIDED
• IPD Plan Description: Participants have agreed or disagreed to share data later. At this moment it is still undecided whether we will share data.

Drug and device information, study documents

• Studies a U.S. FDA-regulated drug product: No
• Studies a U.S. FDA-regulated device product: No