The objective of this study is to evaluate (1) the effect of a non-restrictive satiating intervention on appetite control, body weight loss and maintenance; and (2) determine whether switching to a non-restrictive satiating intervention following a conventional restrictive intervention can prevent increases in appetite and attenuate body weight regain usually observed after weight loss in men and women living with obesity. This is an 18-month, randomized, controlled, parallel weight loss [Phase 1 (P1): 6 months] and maintenance trial [Phase 2 (P2): 12 months] with three groups (n=234 men and women): (1) non-restrictive, satiating intervention (P1) followed by a continuation of this intervention (P2); (2) conventional restrictive intervention (-500 kcal/d) (P1) followed by a non-restrictive satiating intervention (P2); (3) control group that follows minimal healthy guidelines (P1) followed by recommended weight maintenance strategies (P2). All groups will be controlled for physical activity and sleep patterns. The non-restrictive satiating intervention will include guidelines and recipes to prepare highly satiating meals that will be low in energy density and glycemic index and high in protein, polyunsaturated fats, vitamins and minerals (e.g. calcium), and certain constituents of spices (e.g. capsaicin). Measurements at baseline (week 0), after P1 and P2 will include the following primary outcomes: appetite control, weight loss and maintenance; and secondary outcomes: body composition, physiological, psycho and neurobehavioural and health-related variables. Follow-ups will be done by a dietitian every 2 weeks during P1 and once a month during P2.

Inclusion Criteria:

• individuals with a BMI ≥30 and <40 kg/m2
• aged between 18-50 years
• waist circumference >102 cm in men and >88 cm in women.

Exclusion Criteria:

• taking medications that could influence appetite or body weight (e.g. thyroid replacement therapy, sulfonylureas and glucocorticoids)
• being treated with insulin for type 2 diabetes
• large body weight fluctuations (>4 kg over last two months)
• characterized by high restraint behaviour (score >12, measured with the TFEQ)
• history of an eating disorder (e.g. binge eating disorder) using the EDE questionnaire
• performing >150 min of moderate-vigorous intensity physical activity/week
• use of nutritional supplements (multivitamins, calcium, protein, fibre); 8) smoking, drugs or alcohol (>2 drinks/d)
• consumption of >5 cups of coffee/d
• (pre)menopausal or pregnant women
• diagnosis of chronic diseases, acute infections or gastric problems (e.g. ulcers)
• food allergies/intolerances to ingredients/foods in the satiating intervention
• having a pacemaker (for fMRI)
• taking sedatives or sleeping pills
• symptoms of depression (>20 on the BDI).

The research questions will take into account sex and gender as we consider: (i) restrictive and non-restrictive approaches that may have different impacts on body weight between men and women; and (ii) the impact of these interventions may have different outcomes on behavioural and psychosocial variables. Therefore, participants may be able to indicate their gender identity.

Blinding participants is not possible due to the nature of the interventions. Individuals independent from the study and blinded to groups (e.g. statistician), will conduct the randomization and analyses while a research assistant, instructed not to discuss treatments with participants, will conduct the testing sessions.