The researchers, from Cornell University, reviewed hundreds of articles on eating behavior and found that among many subconscious environmental cues that influence what and how much we eat, portion size is among the most powerful. As portion sizes have increased, so has the amount people tend to eat.
“Food choice is an illusion,” wrote David Levitsky, professor of nutritional sciences and of psychology at Cornell, who co-authored the article with graduate student Carly Pacanowski.
They found that a complex combination of factors influenced our food choices, including portion size, variety of foods offered, fat content of the diet, the number of people eating, location, and exposure to food advertising. These all act as ‘food primes’, which cause people to increase their energy intake.
“In combination, these factors are so powerful that, unless we are restrained by surgery or structured eating plans, or by a dedication to prevent future weight gain (restrained eating), we become vulnerable to all stimuli presented, mostly by commercial interests who have learned to effectively use these techniques to encourage us to eat a little more,” they wrote.
The paper claims that such a food environment has emerged since the 1980s, when rates of obesity began to accelerate in the United States. Per capita caloric intake has increased by about 9-30 calories a day since then.
“An individual’s decision to eat is not a result of personal weakness, but rather is determined, to a great extent, by the many environmental cues that have emerged since the early 1980s as a consequence of the commercialization of food,” they wrote.
The authors acknowledge that personal responsibility does play a role, but advocate using it in the context of collective responsibility to change our food environment in order to tackle obesity – and to reject the notion that people are entirely free to choose what they eat.
They wrote: “If we add our personal responsibility to resist food cues to the collective responsibility of government to control the many food signals in our environment…we may amass the power, and the will, to curb the epidemic of obesity.”
The paper is available online here.