Comprehensive Intervention for Changing Eating Habits Through Portion Control

Inclusion Criteria: * Body mass index equal or above 27.5 kg/m2 (26.0 kg/m2 for those of Asian descent), or waist circumference above 84 cm (female) or above 90 cm (male) * Eating home-made meals at least 5 days a week * Physically and mentally fit as assessed by the study researcher * On-going pharmacological and hormonal treatment is accepted when this does not affect the study parameters (e.g., glucose response, appetite), and when the participant has been in a stable dose for at least 3 months * Agreeing to undergo all the study procedures and consume the study foods * Being able to attend in person on 4 clinical investigation days and 2 compulsory group sessions during working hours * Being able to understand and agree to sign the informed consent form Exclusion Criteria: * Being a regular smoker (i.e., smoking more than 4 cigarettes a month) * Being pregnant, breastfeeding or planning a pregnancy * Exceed the weekly alcohol consumption limit for the corresponding sex (more than 14 units in women and more than 20 units in men) * Having followed a meal plan for weight loss and/or muscle mass gain in the 3 months prior to the start of the study intervention * Experiencing a weight change greater than 5% in the last 3 months * History of relevant functional or structural anomalies of the digestive system, such as malformation, angiodysplasia, active peptic ulcer, chronic inflammatory or malabsorption disease, or history of intestinal or bariatric surgery * Suffering from any type of cancer, currently undergoing treatment for cancer, or when a period of at least 5 years has not elapsed since its eradication * On-going chronic metabolic disease or obesity-related disease, or any systemic intestinal, liver or kidney disease such as type 1 or type 2 diabetes, severe dyslipidemia, uncontrolled thyroid function disorder, cirrhosis, inflammatory bowel disease, untreated anemia, etc. (will not be excluded due to "fatty liver") * Active mental health conditions, including dementia, that could interfere with the participant's ability to adequately follow the study protocol, or current use of psychiatric medications that may affect appetite (e.g., antidepressants). For stable-dose participants, cases will be evaluted on a one-to-one basis with the study medical team. * Engaging in 10 or more hours of vigorous physical activity per week. * Being allergic, or being intolerant to the study foods or their ingredients (regular or lactose-free yogurt and granola) * History of anaphylactic reaction to any food * Taking nutritional supplements as a prescription medication that may affect the results of the study * Taking over-the-counter nutritional supplements (that is, without a medical prescription) that may affect the results of the study, unless the person is willing to stop it during the 12 months of the study duration and only when a minimum washout period of 14 days can be guaranteed prior to the basal measurements being taken * A high incidence of attitudes and behaviors associated with eating disorders, expressed as a score greater than 20 on the 26-item Eating Attitudes Test scale (EAT - 26) * Co-inhabiting with a study participant * Previous participation in PORTIONS-3 (preclinical study) or PORTIONS-4 (pilot trial) * For the body composition analysis, wearing a pacemaker or certain metallic implants. ADDITIONAL EXCLUSION CRITERIA FOR SUB-STUDIES Functional MRI sub-study - Additional Exclusion Criteria: * Claustrophobia * Presence of metallic implants, pacemakers, defibrillators, or other devices incompatible with functional magnetic resonance imaging (fMRI) * Body weight greater than 180 kg * Neck circumference greater than 62.8 cm * Any contraindication to undergoing magnetic resonance imaging identified through the MRI safety screening questionnaire * A score of 50% or lower for four or more of the food items included in the auditory stimuli in the food liking questionnaire, indicating insufficient familiarity with the stimuli * Allocation to the trial's focus group discussions, unless the participant explicitly expresses a willingness to participate in both the fMRI assessment and the focus group discussions Gut microbiota sub-study - Additional Exclusion Criteria During the 15 days preceding stool sample collection: * Use of antibiotics * Use of fiber supplements * Use of supplements that may affect the gut microbiota, such as probiotics or biotin