An experiment with psychology students showed that stress increases the tendency to make unhealthy but palatable food choices. A prior commitment to making healthy food choices negated that effect. But in each case, study participants were far more likely to choose palatable but unhealthy foods than healthy but not palatable foods. The paper is psychoneuroendocrinology.
Precommitment is a strategy in which a person makes decisions in advance to limit future choices. This is used when you anticipate that someone may act against their long-term interests at this time. By setting up barriers and rules in advance, precommitment helps protect a person from temptation, impulsivity, and weakness of will.
A common example is setting up automatic savings so that money is moved before it is spent. Another example is removing distractions before working, such as blocking social media or putting your phone in another room. In all of these cases, precommitment helps align immediate actions with long-term goals. Pre-commitment can be personal, such as a promise you make to yourself, or external, such as signing a contract or using a commitment device.
It is when choosing what and how much to eat that people often make choices that are against their long-term interests. In such cases, people often choose tasty but not healthy foods over healthy but not very tasty foods. This is especially common when people are stressed, tired, or generally in a bad mood.
The study’s lead author, Paul A.G. Forbes, and his colleagues investigated whether advance commitments could help people stick to their desire to eat healthy. They developed a procedure in which participants reviewed the foods in advance and later chose whether to remove the option of eating the unhealthy food.
The final analysis included 29 psychology majors (out of 35 initially recruited). Their average age was 22 years and 25 were women. They completed two experimental sessions on average 16 days apart.
At the beginning of the study, participants completed an online survey in which they rated 285 foods on how healthy, tasty, and appealing they found them. They also reported how often they ate different types of food and completed assessments of self-regulation of eating behaviors, impulsivity, and metacognitive prospective memory.
Based on the results of the food questionnaire, the study authors created 96 food pairs, consisting of one item that participants rated as healthy but not tasty, and one item that participants rated as tasty but not healthy. If a participant had never eaten meat or fish, foods containing those ingredients were removed from the set before pairing. In the end, the study authors created 96 individual sets of foods for each participant.
Study participants completed the experiment twice under two different conditions. One was a stress condition, in which participants alternated between keeping their hands in very cold water and having to complete mental arithmetic tasks under pressure, while being made to believe they were being recorded and an experimenter gave negative feedback. This is designed to induce stress. In a stress-free state, they dipped their hands in soothing warm water and performed simple counting tasks without being judged. Each experimental condition involved running this treatment twice.
After the initial stress induction or control procedure, participants completed the precommitment phase of the experiment. At this stage, we observed the previously created food pairs. In some cases (called viewing tests), they were simply shown a pair of foods. In other cases (restriction trials), participants were given the option to remove unhealthy foods from subsequent choices. After this, they performed the stress-inducing task again (or the warm water task, depending on the condition they had completed) and proceeded to the choice phase.
During the choice phase, participants revisited the food pairs from the pre-commitment phase, but this time they had to choose which food they wanted to eat from the pair. For the food combinations included in the viewing trials, both food options were available as potential choices. The same was true for pairs of restriction trials in which participants did not choose to remove the less healthy item. However, in pairs where they chose to remove the unhealthy item, participants could only select the healthy item.
The results showed that participants chose palatable but unhealthy foods much more often than healthy but not palatable foods. In viewing trials, the healthier option was chosen on 21% of trials, but this rose to 30% in restricted trials. However, it should be noted that during the choice phase, in trials where participants had previously decided to eliminate unhealthy foods, they actually had no choice and their only option was to choose healthy foods.
The results showed that when participants were under stress, they were more likely to choose less healthy but tasty foods. However, while this effect was present in viewing trials (when participants only saw the food combinations initially), it was not present in choice-restriction trials (when students had the option to remove the less healthy food early on).
“Although the tendency to choose more unhealthy but palatable foods increased with subjective stress, this effect was counteracted by stress-related increases in precommitment. Our findings therefore demonstrate the effectiveness of precommitment under stress. This has important implications for interventions aimed at promoting healthier food choices, especially in stressful environments, and may particularly benefit individuals with low dietary restraint,” the study authors concluded.
This study contributes to scientific understanding of the psychology of food choice. However, it should be noted that once the decision was made to exclude food during the pre-commitment phase, participants no longer had a choice during the choice phase of that particular trial. This perfectly mirrors how pre-commitment to force healthier choices later works in real life, but it emphasizes that the success of this strategy is entirely dependent on the initial willingness to limit one’s own options. Additionally, this study was conducted on a very small group of psychology students. Results from studies of larger, more demographically diverse groups may not be identical.
The paper, “Precommitment promotes healthier food choices under stress,” was authored by Paul AG Forbes, Candace M. Raio, and Tobias Kalenscher.
