Eating with a fat friend 'makes you eat more'

“Sitting next to overweight people makes you more likely to gorge on unhealthy food,” the Daily Express reports.

The paper reports on a small-scale research experiment showing that the presence of an overweight woman (an actress in a fat suit) near a buffet made student volunteers choose and eat a larger amount of unhealthy food (spaghetti) than when she was a healthy weight (without the fat suit). This effect was not influenced by whether the actress chose to eat healthily or unhealthily herself, something the study also looked at.

The researchers’ explanation of this was, “that when eating with or near an overweight person, you may be less likely to adhere to your own health goals.”

The study was not wholly convincing and does not prove this phenomenon exists in the general population, where food and social interactions may be more complex and nuanced. Food choice was artificially restricted to just two foods: spaghetti and salad – not the best buffet going. The same results may not have been found if participants were given a more realistic range of food choices.

It is difficult to see what practical implications the study "brings to the table", other than to be conscious of your own food choices, regardless of the social situation.

This may be a poignant reminder to those looking to maintain a healthy weight that when it comes to “all-you-can-eat” situations, it’s probably best to regard it as a special offer, not a personal challenge.

Where did the story come from?

The study was carried out by researchers from Southern Illinois University and Cornell University (US). No funding source was mentioned in the publication. The study was published in the peer-reviewed science journal Appetite.

The Express generally covered the story accurately, though the headlines indulged in a bit of “fat shaming”, as eating a small extra amount of spaghetti was morphed into “greed”.

What kind of research was this?

This was a randomised, single blind, human study looking at the influence of an overweight eating companion on healthy and unhealthy eating behaviour.

The researchers indicated that many social factors influence food intake, such as the presence or absence of eating companions, as well as the body type of these companions.

This study aimed to investigate the effect of:

• the presence of an overweight person on what other people chose to eat
• whether this was influenced by what food (healthy vs. unhealthy) the overweight person served themselves

What did the research involve?

The research team recruited 82 undergraduate college students (average age 19.5 years; 40 women and 42 men) to eat a buffet meal restricted to spaghetti with meat sauce and or salad at lunch. They also enlisted an actress to wear a suit that added three-and-a-half stone (50 pounds) to her weight. Without the “fat suit” she was a healthy weight, but donning the fat suit put her at the border of overweight/obese categories (with a BMI of 29.3).

Each of the 82 participants was randomly assigned to one of four scenarios:

• the actress served herself healthily (more salad and less pasta) while wearing the fat suit
• she served herself the same healthy meal without the fat suit
• she served herself less healthily (more pasta and less salad) while wearing the fat suit
• she served herself the same less healthy meal without the fat suit

Participants in each scenario viewed the actress serving herself and then served themselves pasta and salad.

The actress was not known to the participants, but drew attention to what she was eating by asking out loud “do I need to use separate plates for pasta and salad?” and dropping her fork and asking for a new one. She also sat in full view of the buffet queue.

The first part of the study looked at the effect of the fat suit. The second part of the study looked at the influence on the participants’ food choice when the actress served herself either a small amount of pasta and a large amount of salad (described as the “healthy eating condition”), or a large amount of pasta and a small amount of salad (“unhealthy eating condition”).

Participants were asked to report the number of hours and minutes since they had last eaten, to control for their hunger prior to the experiment.

The participants knew that the study aimed to examine eating behaviour, including serving size and intake, but they were blinded to the scenario allocation of the actress. When asked, no participants revealed suspicion about the purpose of the study.

What were the basic results?

These were two main findings:

• When the actress wore the fat suit, appearing overweight, the other participants served and ate more pasta regardless of whether she served herself mostly pasta or mostly salad, compared to when she was of normal weight.
• When she wore the fat suit and served herself more salad, the other participants actually served and ate less salad.

This meant that, regardless of whether the actress served healthy or unhealthy food, participants served and ate a larger amount of pasta (unhealthy food) when she appeared overweight than when she appeared a healthy weight.

How did the researchers interpret the results?

The research team said their results “support the ‘lower health commitment’ hypothesis, which predicted that participants would serve and eat a larger amount of pasta when eating with an overweight person, probably because the health commitment goal was less activated.” They added that their, “results did not support the ‘avoiding stigma’ hypothesis, which predicted that participants would serve and eat a smaller amount of pasta when an overweight confederate served herself unhealthily, to avoid association with the stigmatised group”.

Conclusion

This small-scale research experiment found that the presence of an overweight woman (an actress in a fat suit) near a buffet made student volunteers choose a larger amount of unhealthy food than when she was a healthy weight (without the suit). This effect was not influenced by whether the actress chose to eat healthily or unhealthily herself.

These findings suggest that people may serve and eat larger portions of unhealthy foods and smaller portions of healthy foods when eating with or near an overweight person. The researchers did not test out any reasons for this, but speculated this might be, “because they are less in tune with their own health goals”. They said this phenomenon might be easy to avoid by “assessing your level of hunger before going to the restaurant and planning your meal accordingly”.

However, the study was not wholly convincing and doesn’t prove this phenomenon exists in the general population, where food and social interactions may be more complex. For example, the study was restricted to a relatively small amount of young American adults (average age of 19.5), which may not be representative of findings in older people, children or other countries and cultures.

Similarly, the study investigated a single eating scenario, a buffet, where food choice was artificially restricted to only two foods to help the study design. The same results may not have been found in other eating scenarios, or if participants were given a more realistic range of food choices at a buffet. In addition, they did not measure how much cheese or salad dressing was used, which could have a substantial impact on whether the meal was healthy or unhealthy.

The study participants were also aware that their serving and intake levels were being recorded, which may have influenced the results.

Anyone who has been to an all-you-can-eat buffet and over-indulged can probably recognise how the social context of a meal can influence the amount of food people eat. This study suggests a further influence, body type, may also be influential, but only tentatively. This phenomenon is likely to be the subject of future research.