Recently, an interesting piece of research was published in the journal Appetite (1), that demonstrated that we could be underestimating the effect of external influences (such as portion size) on food intake, when researchers examine participants under laboratory conditions instead of in the real-world. This research was an exciting collaborative effort between researchers within the Appetite and Obesity Research Group at the University of Liverpool, and undergraduate students that took part in the University summer research internship scheme from the University of Liverpool and University of Calgary.
Eating behaviour researchers have used tightly-controlled laboratory research to consistently demonstrate that external influences (such as the size of our food portions) can affect our food intake (2). However, it is important that we now acknowledge that eating behaviour in a laboratory is artificial, as participants are especially aware that their behaviour is being measured. This is problematic because this heightened awareness of being observed in laboratory settings, causes people to restrict their food intake, as they are more concerned with how they are presenting themselves (3). Hence, it is crucial that we recognise that traditional laboratory-based research may not accurately capture the effect that these external influences could have on our food intake in the real world.
In this new paper, we directly examined an external factor that influences food intake (manipulating portion size) across two environments: in a standard laboratory vs in real world settings, using the same procedure, participants and test foods. Two studies were conducted, with the same standard laboratory setting and two different real-world settings. Study 1 examined food intake in a naturalistic setting (participants home), while Study 2 used a semi-naturalistic setting (a laboratory designed to resemble a lounge setting). This second study was conducted in order to measure environmental differences in food intake with greater certainty that participants complied with study instructions.
In both studies all participants completed two test sessions in each environment, eating a portion of popcorn (small or large, consuming the same portion size in both sessions) whilst watching an episode of Friends – perfect afternoon, right? We used a cover story to ensure that participants were not aware that we were measuring food intake. Specifically, we told participants that we were investigating consumer experiences of a new snack food product when consumed in different eating contexts.
The standard laboratory session required participants to sit alone, partitioned off in a small testing booth with just a table and chair. For Study 1 in the real-world condition, participants were given a test pack (including the portion of popcorn and TV clip) in order for them to complete this test session in their own homes, and were given instructions to consume the popcorn alone, only whilst watching the TV clip, and with no other distractions. Study 2 differed from this, as the real-world session took place in a University laboratory that was designed to resemble a lounge (a semi-naturalistic setting) which was furnished with a sofa, coffee table, bookcase, television and rug, where the researcher was present to give instructions to the participant.
In Study 1, we found that portion size had a larger influence on food intake when participants ate in the home setting, than in the standard laboratory – the portion size effect was greater in the real-world setting. Also, participants in Study 1 reported feeling more relaxed when eating at home than in the standard laboratory.
Study 2 found no evidence that the influence of portion size on food intake was different between the semi-naturalistic setting and the standard laboratory. Possibly because both laboratories used in Study 2 were in a research building and involved close interactions with an experimenter. Findings in Study 2 indicated that participants regarded these laboratories as similar, as they reported feeling equally publicly self-aware (concerned with how they were presenting themselves) across environments. As a number of studies have used similar semi-naturalistic eating laboratories (4, 5), future research should examine whether or not these settings effectively resemble real-world eating environments.
Overall, the findings of this research suggest that any previously observed factor that influences food intake (such as portion size) could be underestimated when measured in a laboratory environment. So, if we want eating behaviour research to accurately guide public health policy, it is important that we take our research ‘out of the lab and into the wild.’ Click here to read the full article.
Contribution by Katie Clarke, MPsycholSci student at the University of Liverpool.