Implementing strategies for changing eating habits based on controlling serving size: methodological development and pilot study.
Related links:
Artículos científicos
Libro
Comunicaciones en congresos
Trabajos de fin de grado relacionados con el proyecto
Trabajos de fin de máster relacionados con el proyecto
The primary goal of the PORTIONS-4 project was to test the effectiveness of a set of hypothetical and practical strategies focused on providing healthy and balanced food to people who are overweight. A second goal was to identify potential barriers that can affect that population’s adherence to weight loss programmes, and consequently their effectiveness. The results have made it possible to advance knowledge about what kind of strategies can be effective for changing habits in the context of a nutritional intervention focused on improving habits, including eating, physical activity and managing emotions. The findings are equally relevant for the general population, both for maintaining good health and preventing future complications associated with lifestyle. In addition, the project was complemented by the development of new technologies based on capturing and processing images that can be applied according to eating behaviour both inside and outside the laboratory.
Why was this project done?
For most people it’s hard to remember what we ate at our last meal. That’s because we often eat almost unconsciously, at work, in front of the television or having dinner with friends. Given that 90% of what we are served tends to be consumed, choosing the food and especially the amount, is a crucial step if someone wants to improve their diet. Along those lines, having practical instruments that guide us about what and how much to serve in a direct visual way without having to use a scale or count calories can be an attractive strategy.
In our previous research (PORTIONS-1, 2 and 3), we showed that using calibrated plates, spoons, and olive oil dispensers that show amounts using visual marks or restricting volume can help consume fewer carbohydrates, less oil and, in some cases more fruit, when used correctly to serve a meal or as part of a laboratory experiment. Given that we don’t behave the same way when we’re being observed as when we’re at home, in a café or in other people’s company, and that our habits can also change over time, the results must be checked outside of the laboratory, in an everyday context and over a long period of time.
On the other hand, properly studying how we behave with food in our natural environment is an open challenge in behavioural research. The data obtained in laboratory studies has the advantage of being reliable, because it’s largely free of artefacts. That means in those trials, the influences that can obscure the results are controlled in order to have greater certainty that the effects observed are due to exposure to the factor being studied and not something else. Nevertheless, that strictly controlled environment makes the studies not be very representative of real life, and they can even cause changes in our behaviour without us realising it, especially in regards to eating. Until now, sophisticated observation systems based on commercial glasses have been used in our projects. The high cost of the glasses and their high sensitivity forces us to do experiments in laboratory conditions, which limits the scope of the results obtained. That is why it’s essential to explore new methods that can be used outside the laboratory and that make analyses in more natural and spontaneous conditions possible, while maintaining an acceptable level of precision.
What was researched?
Two main tasks were carried out in this project. On one hand, a medium-term clinical trial was done to study the impact of a global intervention focused on changing habits, and in particular controlling servings with overweight people (trial led by the UNAV). On the other hand, the use of image capturing technologies for remote analysis of eating behaviour was explored (task led by the UPNA).
In the PORTIONS-4 clinical trial the effect of a calibrated spoon and olive oil dispenser on diet and body composition markers was studied in 40 overweight or obese adults as part of a 6-month weight loss programme. The participants used the instruments in a natural setting to prepare and serve their own recipes at home, and monitoring was done by phone every 15 days by research staff, in addition to clinical monitoring every 3 months.
All the volunteers also had a mobile app for support (at three months), and a physical guide (from the start), developed by our dieticians-nutritionists and psychologists with practical guidance about using the instruments, in addition to information about food, movement, and emotional well-being. The participants filled out bi-weekly forms to record their meals and usage of the instruments. And they had three clinical visits where their body composition, glucose (sugar) levels, cholesterol, and blood fat were measured, as well as their feelings of hunger and satiation, knowledge of balanced means, and the capacity to control their impulses to eat tasty food, using a computer test and electroencephalography (a technique to measure brain activity).
 |  |
 |  |
Furthermore, a randomly selected group of eight participants was invited to attend a 90-minute group session where their opinions about the obstacles and facilitating elements of the intervention three months after starting the programme were collected.Lastly, a survey to evaluate the programme was given to all the participants who kept up with it to the end.
In regards to technological development, at the UPNA they have been working on eye-tracking techniques which, alongside other physiological methods, (e.g. electroencephalography), make possible an objective analysis of the processes involved in control over eating. That kind of data is interesting because it makes it possible to approximate the level of a person’s attention in a non-invasive way.
Main Findings
In general, the PORTIONS-4 clinical intervention was judged positively by the participants, who rated their satisfaction with the organisation and design of the study with 9.2 points out of 10. They also rated aspects like usefulness, logic, and the likelihood of continuing very well (higher than 8 of out of 10). These results, however, were obtained using the subsample of participants who completed the study and the final evaluation survey, which was only 23 people due to the high abandonment rate, which was around 40%. The drop-outs happened mostly at three months into the intervention, and they included both men and women regardless of their body mass index (BMI) or nutrition profile features. The most common reasons for leaving were schedule incompatibility, mobility, expectations, and the self-applied nature of the intervention.
The participants reported using the guide and app more right after receiving them, while the spoons and olive oil dispenser were used more continuously, being most commonly used together during midday meals followed by just using the olive oil dispenser at dinner. Among the 23 participants who reached the end of the intervention, a slight improvement in body composition was observed, especially in waist circumference. However, as with weight and BMI, the difference was not statistically significant, possibly due to the reduction in the sample size. No changes over time of physiological markers (glucose, insulin, hormones), or feelings of hunger or satiety were observed.
On the other hand, an improvement in knowledge about balanced meals was detected. Knowledge was high from the start, but it improved at the end of the study, which suggests that the participants retained part of the theoretical nutritional education provided. That result was confirmed with the ingest data analysed for the first 16 volunteers, which indicated an increase in water consumption, a reduction in calorie consumption (fewer carbohydrates, protein and fat), and a decrease in energy density in the diet in general. These findings are promising, because they confirm the effectiveness of the intervention as long as it is followed strictly enough.
Insofar as the capacity for impulse control, the computer test showed better inhibitory control with photographs of food than with objects (e.g. office, cleaning or sports material). That could suggest greater familiarity with food, or even a bias towards it, in the study population (overweight adults). Currently, that data still needs to be compared with the cortical cerebral cortex data, but for the time being it has been determined that the encephalography test showed high general precision (>95%) under all conditions.
The results of the group sessions confirmed that the intervention was well received. The participants described it as easy, practical, and adaptable. They highlighted benefits like controlling servings and an increase in energy from reducing sugar. Nevertheless, they also pointed out difficulties, like using the instruments away from home, consistency with recording, and technical problems with the mobile app. The tools, like the measuring spoon and olive oil dispenser, had mixed judgements and improvements were proposed, like including simple graphics in the app to make it easier to track progress. The study made it possible to identify key aspects to improve future interventions of this kind.
In regards to technology, the PORTIONS-4 project has taken the first step towards obtaining an eye-tracking system that works in non-controlled conditions outside the laboratory based on a low-cost tray with a built-in camera that makes it possible to remotely analyse a user’s gaze without using specific devices on the user.
Conclusions and Future Steps
The process of changing habits is a major challenge for most people, in particular if the habits involve our way of interacting with food. In order for a weight loss programme to be effective, in addition to just starting changes, they must be maintained over time. This project has confirmed those trends, and also made it possible to gain knowledge about which psychological, nutritional and technological strategies can be most effective when designing new interventions of this type, and which difficulties or obstacles should be taken into consideration, including ones that lead people to give up.
The next step in our research will be to improve those strategies and technologies and test them with a larger sample of the overweight population, in addition to using a control group that gets the same level of monitoring but without the experimental instruments (spoons, book, etc.), to make it possible to better quantify the impact of every component on patients’ health. In the new project, the mechanisms of the intestine-brain axis involved in regulating hunger and weight loss will also be analysed. And new versions of the eye-tracking technology with improved capacity for detecting stimuli in a domestic setting will be explored. The new project, PORTIONS-V, has financing from the Navarre government and is scheduled to start in 2026. More information will be available here starting in September 2025.
