Study justification:~The prevalence of obesity and associated health-risks (e.g. cardiovascular disease, diabetes and cancer) continues to increase across the globe, raising the need for effective weight management strategies to improve the population´s health. High rates of obesity respond at least in part, to the current obesogenic environment that prompts people to overeat both in terms of energy and amount. In this context, access to practical tools that can help individuals control their portion sizes represent a promising, cost-effective strategy. However, urging people to eat less of all foods might be challenging as individuals are used to consume a certain volume of food to feel satisfied. Instead, a more effective approach may be to help people lower the energy density of their meals through the increase in the amount of fruits and vegetables in their diet at the expense of high energy density foods, such as foods rich in fat and starch. Portion-control plates and serving utensils, designed to measure the appropriate amounts and proportions of main food groups (e.g. starch, protein and vegetables), can actually facilitate this shift. Our recent systematic review (https://pubmed.ncbi.nlm.nih.gov/34207492/) found that portion-control plates in particular were the most promising tools to regulate intake and develop healthier eating habits. However, some of the studies conducted up to date have explored the effect of different portion control tools in combination with other weight management strategies, making it difficult to determine the impact of these instruments on their own. The design of the tools may also negatively affect success if instruments don´t fit the user´s lifestyle and eating routines. Individual characteristics such as sex and BMI have also been found to modulate the success of portion control tools. Therefore, optimizing the current tools is needed to achieve a wider impact.~Specific aims:~The primary goal of the present study is to investigate the acute effects of using a portion control tableware toolkit, optimized based on our previous quantitative and qualitative work with portion control tableware, in people with overweight and obesity. The intervention will be conducted under controlled laboratory conditions in order to obtain proof of concept of the toolkit efficacy before application into field studies. The secondary goal is to gain knowledge on the cognitive and physiological mechanisms involved in portion size regulation mediated by portion control tools.~It is expected that the findings from this study will shed light into the cognitive and physiological processes associated with portion control. It may also help to explain individual variations in the responses to obesogenic environments, which will hopefully lead to improved personalized interventions. The ultimate goal is to develop effective, easy, attractive and affordable strategies that could help individuals prevent overeating.~Study design:~This will be a non-randomized within-subjects laboratory study which will involve two sessions, of approximately 3 - hour duration each, conducted at lunchtime at the Center for Nutrition Research of the University of Navarra (Pamplona) on two different days, with a 7 to 11 day wash-out period. At each session, participants will be invited to self-serve and eat a lunch from a cold buffet in the laboratory. On day one, participants will self-serve and season their food using control tools (conventional kitchen serving spoons and oil dispenser). On day two, participants will be invited to self-serve the same foods as on day one but using experimental tools (calibrated portion control serving spoons and calibrated oil dispenser). On both days, the food will be served on a standard (25 cm in diameter), white dish without markings or illustrations, and participants will eat using standard cutlery. A set of cognitive tests will be completed before, during and after the meal. All participants will receive a give-away tool in compensation for their time.~Study procedures:~100 mm visual analogue scales (VAS) will be used for hunger-satiety assessment prior to the meal intake, immediately after finishing the meal and at 30, 60, 90 and 120 minutes after finishing the meal.~Blood extractions will be carried out at 0 (fasting), and then 7, 12, 32, 62 and 92 minutes after commencing the lunch. Blood levels of glucose, insulin, pancreatic polypeptide and total ghrelin will be used as biomarkers of satiety/hunger.~A wearable Tobii eye-tracking device will be used during the self-serving activity to infer cognitive effort associated to the serving task from total and average fixation durations, fixation count, time to first fixation and pupil dilation.~A computerized memory reconstruction task will be completed by participants 120 minutes after beginning meal intake to measure the accuracy of the participants' recall of the food amounts consumed. Specifically, visual representation through selected images of the previously consumed amounts (recalled portion size) will be compared to actual amounts consumed after the use of each set of tools (consumed portion sizes).~A food diary will be kept by participants up to bed-time after they leave the laboratory on each study day to monitor energy and macronutrient intake, plus compensatory eating behaviour.~A computerized learning reconstruction task, aimed at recreating a balanced meal using images of foods, will be completed by participants before going to bed.~Questionnaires will be used to evaluate the intention to change one's eating habits after using the experimental tools, perceived cognitive effort when using experimental tools, toolkit acceptance, and to compare participants' habitual portion sizes (portion size norms) with the ones selected in the laboratory.~An observation task will be conducted at the end of visit 2, to collect participants' opinions about 3 additional portion-control utensils developped/chosen based on our previous qualitative study (a multi-compartment lunchbox, a portion-control melanine dish and a measuring cup for dry food).~Experimental buffet:~The experimental buffet has been designed to include foods from each of the main food groups in line with the USDA MyPlate model. The foods include: vegetables (cherry tomatoes, green leaves and bell pepper), protein (cooked chopped chicken breasts, canned tuna and mozzarella cheese pearls) a starchy food (cooked quinoa and pasta). Chickpeas are also included as starchy food although they contain some protein. Fruit including apples, oranges and canned pineapple, is included as optional dessert. Complimentary bread, condiments (olive oil, salt, and pepper) and non-carbonated water will also be offered.~All foods and water will be served cold (or at room temperature) on separate trays set up in a buffet-style and in sufficient amounts to allow eating until comfortably full and to avoid ceiling effects (e.g. at least double the amount of the average portion). To standardize the two study conditions, participants will be asked to select the same foods on both laboratory visits. Each participant will choose his/her own experimental meal during the screening session, thereby preventing any unnecessary food waste.~Recruitment and Screening:~The sample size for this study was estimated using the open source software GPower. For a 2-sided paired comparison, a sample of 34 completers would allow detection of significant between-conditions differences, with alpha 0.05 and 80% power, in variables related to selected portion size (main outcome measure: consumed carbohydrate portion size), cognitive effort, and cephalic and intestinal satiety responses. Assuming a 15% drop-out (based on an observed 10% rate in our previous study) the recruitment target will be 40 healthy adults with overweight or obesity. Whenever possible, a balanced representation of men and women will be ensured, so that neither sex constitutes more than 60% (or less than 40%) of the sample. Potential participants will be recruited through advertisements in the local press, through social media, university newsletters, at health and community centres, pharmacies, shops, schools, etc., and from the volunteer database from the Center for Nutrition Research of the University of Navarra.~Initial verification of the inclusion/exclusion criteria will be performed via a telephone interview. If the initial criteria are met, candidates will be sent via email a link and ID code to complete the Eating Attitudes Test (EAT-26) and the Perceived Stress Scale (PSS-14) online, via Google Forms. Those who meet the EAT-26 and PSS-14 criteria (see Eligiblity Criteria section) will be invited to the screening session in the laboratory for anthropometric measurements, experimental food tasting, and an eye-tracking familiarization test.~Assessment:~The following questionnaires will be administered to collect data for later sample description and analysis of potential variables that could influence eating habits and hence study results:~Socio-demographic questionnaire.~NEO Five-Factor Inventory (NEO-FFI), to assess the central domains of normal personality~Profile of mood states (POMS), to explore potential impact of emotions on eating behavior.~Trait meta-mood scale (TMMS-24), to measure of emotional intelligence~Three-factor eating questionnaire (TFEQ), to measure the three dimensions of human eating behavior (dietary restraint, disinhibition and hunger)~Beverage consumption habits (BPS), to explore beverage portion size awareness and consumption habits.
Obesity has reached epidemic proportions globally, alongside its associated comorbidities including cardiovascular diseases, diabetes and cancer. Effective weight management strategies are thus paramount to improve the population´s health. One of the key causes of obesity lies in excessive energy consumption derived from eating too large portions of food. In this context, practical tools to control portion size represent a promising, cost-effective strategy.~This study will investigate whether using an optimized portion-control toolkit to consume a meal under controlled laboratory conditions has a positive effect on the nutritional quality of the meal as well as any benefits in physiological, cognitive, affective and behavioural outcomes.~The study will involve 40 volunteers with overweight or obesity who will attend two lunch sessions at the Center for Nutrition Research of the University of Navarra (Spain) on two different days. At each session, participants will be invited to self-serve and eat a lunch from a cold buffet. On day one, participants will self-serve and season their food using control tools (conventional kitchen serving spoons and oil dispenser). On day two, participants will self-serve the same foods as on day one but using experimental tools (calibrated portion-control serving spoons and calibrated oil dispenser). A set of cognitive tests will be completed before, during and after the meal.~Conventional and experimental tools will be compared in terms of the following variables: meal portion size and energy density, cognitive effort while serving food, cephalic and intestinal satiety responses, appetite sensations, energy adjustment post-meal, awareness of the quantities of the previously consumed foods and recalibration of portion size norms. Additionally, the study will explore acceptance for and intention to use the optimized portion control toolkit, as well as intention to change eating habits.~It is expected that the findings from this study will shed light into the cognitive and physiological processes associated with portion control. It may also help to explain individual variations in the responses to obesogenic environments, which will hopefully lead to improved personalized interventions.