An experiment involving psychology students showed that stress made them more likely to choose less healthy but tastier food. Precommitment to choose healthy foods counteracted that effect. However, in all cases, study participants chose tastier, but less healthy foods much more often than healthy, but less tasty foods. The paper was published in Psychoneuroendocrinology.
Precommitment is a strategy in which a person makes a decision in advance to limit their future choices. It is used when someone expects that, in the moment, they may act against their long-term interests. By creating barriers or rules ahead of time, precommitment helps protect a person from temptation, impulsiveness, or weakness of will.
A common example is setting up automatic savings so money is moved before it can be spent. Another example is removing distractions before working, such as blocking social media or putting a phone in another room. In all these cases, precommitment helps align immediate behavior with longer-term goals. Precommitment can be personal, such as making promises to oneself, or external, such as signing contracts or using commitment devices.
One area where people often make choices that go against their long-term interests is when choosing what to eat and how much to eat. In such cases, people often choose tastier foods that are less healthy, rather than foods that are healthier but not as tasty. This happens particularly often when people are under stress, tired, or generally in a bad mood.
Lead study author Paul A.G. Forbes and his colleagues investigated whether precommitment can help people abide by their desire to eat healthily. They developed a procedure where participants viewed food items in advance and chose whether to remove the option of having less healthy food items later.
The final analysis included 29 psychology students (out of 35 initially recruited). Their average age was 22 years, and 25 were women. They completed two experimental sessions that were, on average, 16 days apart.
At the start of the study, participants completed an online questionnaire in which they rated 285 food items on how healthy, tasty, and tempting they found them to be. They also reported how often they ate different types of food and completed assessments of self-regulation of eating behaviors, impulsiveness, and metacognitive prospective memory.
Based on the results of the food questionnaire, the study authors created 96 pairs of food items consisting of one item that participants rated as healthier but less tasty and one item that they rated as tastier but less healthy. If participants never ate meat or fish, food items involving those ingredients were removed from the set before creating the pairs. In the end, the study authors created 96 pairs of food items for each participant individually.
Study participants completed the experiment twice, under two different conditions. One was the stress condition, during which participants alternated between keeping their hand in very cold water and having to complete a mental arithmetic task under pressure, while being made to believe that they were being recorded and while an experimenter was giving them negative feedback. This was designed to induce stress. In the non-stress condition, they immersed their hands in pleasantly warm water and did a simple counting task without anyone evaluating them. Each experimental condition included two runs of this treatment.
After the first stress induction or control procedure, participants completed the precommitment stage of the experiment. In this stage, they viewed food pairs created earlier. In some cases (called viewing trials), they were just shown a pair of foods. In other cases (the restriction trials), they were given the option to remove the less healthy foods from later choices. After this, they completed another run of the stress induction task (or of the warm water task, depending on the condition they were completing) and proceeded to the choice stage.
In the choice stage, participants again viewed the pairs of foods from the precommitment stage, but now needed to choose which food from the pair they would like to eat. In food pairs that were included in the viewing trials, both food options were available as potential choices. The same was the case with pairs from restriction trials in which participants did not choose to remove the less healthy item. However, in pairs where they did choose to remove the less healthy item, participants could only choose the healthy item.
Results showed that participants selected tastier, but less healthy foods much more often than healthier, but less tasty choices. In viewing trials, healthier choices were selected in 21% of trials, while this rose to 30% in restriction trials. However, it should be noted that, in the choice stage, in trials in which participants decided earlier to remove the less healthy food, they did not really have a choice—the only option was to select the healthy food item.
The results showed that participants’ propensity to choose less healthy but tastier foods increased when they were under stress. However, this effect was present in viewing trials (where participants initially just viewed the food pairs), but absent in restriction trial choices (where students had an option to remove the less healthy food in the earlier stage).
“The propensity to choose unhealthier but tastier food to eat increased with subjective stress, but this effect was counteracted by stress-related increases in precommitment. Thus, our findings show the effectiveness of precommitment under stress. This has important implications for interventions aimed at promoting healthier food choices, especially in stressful environments, that could particularly benefit individuals with lower dietary restraint,” the study authors concluded.
The study contributes to the scientific understanding of the psychology of food choices. However, it should be noted that after deciding to exclude a food item in the precommitment stage, participants no longer had a choice in the choice stage in that particular trial. While this perfectly mirrors how precommitment works in real life—by forcing a healthier choice later on—it underscores that the success of this strategy relies entirely on the initial willingness to restrict one’s own options. Additionally, the study was conducted on a very small group of psychology students. Results of studies on a larger and demographically more diverse group might not be identical.
The paper, “Precommitment promotes healthier food choices under stress,” was authored by Paul A.G. Forbes, Candace M. Raio, and Tobias Kalenscher.
