You think you're in control of your eating behavior-- but you aren't
In 2005, Brian Wansink's research group published a remarkable study that demonstrates the powerful unconscious influence of the food environment on our consumption (1).
Volunteers were invited to a test kitchen to eat bowls of tomato soup for lunch. Each person was given a bowl containing 18 ounces of soup-- but there was a catch. Half the volunteers were given custom-made soup bowls that partially refilled as they ate, such that the soup level dropped more slowly.
At the end of the experiment, people with normal bowls had eaten 8.5 oz of soup before calling it quits-- a little bit less than a typical 10.5 oz can. People with refillable bowls, in contrast, kept eating and eating-- only stopping after 14.7 oz of soup! The visual perception of having more soup remaining in the bowl caused them to eat 73 percent more soup, and 73 percent more calories. Even more remarkable, both groups reported similar levels of satiety (fullness) following the meal.
This and many other related experiments are described in Brian Wansink's book Mindless Eating, which I found quite thought-provoking despite having picked on it a little bit in an earlier post (2). The research he presents shows that many subtle factors in our food environment influence our food choices and intake, sometimes in major ways. Portion sizes, how a food is packaged and named, variety, and food cues are some of the major topics he discusses. Some of this should be familiar to regular WHS readers.
One of my favorite topics, and one I've been thinking more about lately, is the effort/resource cost of food, in other words, convenience and price.
Would you walk a mile for a caramel?
In a section with this title, Dr. Wansink offers us a one-sentence summary of a classic obesity research book titled Obese Humans and Rats*:
The more hassle it is to eat, the less we eat.
This is a disarmingly simple, yet extremely powerful statement.
In many of my public talks, I have the audience do a thought experiment with me. Imagine you're at work, and there's a plate of brownies (or whatever tempting unhealthy food you prefer) within arm's reach of you all day. What's the likelihood that you'll eat a brownie? For most people, the likelihood is extremely high. Now, imagine you have to walk across the street and pay $6 for the same brownie in a coffee shop. What's the likelihood you'll eat a brownie now? Probably low.
Dr. Wansink presents a variety of findings supporting this concept. Even small differences in the amount of effort required to eat have a large influence on consumption. When consumption is made almost effortless, intake increases substantially.
The implications for calorie intake and body fatness are obvious. A hunter-gatherer who has to climb a tree to obtain a small piece of fruit will require more motivation to engage in that activity than a person who has a large apple within arm's reach. Where does that motivation come from? Much of it comes from fuel depletion-- as signaled by hunger. Therefore, a hunter-gatherer has to experience a greater degree of fuel depletion, and a greater degree of hunger, to be sufficiently motivated to obtain food that requires effort to secure. When she does find food, she'll probably eat less of it, because the motivation of hunger will only outweigh the effort required to climb the tree until she's moderately full-- not stuffed. Therefore, she'll tend to eat a moderate amount of food overall, and energy intake will be appropriately linked to energy needs.
You can apply the same thought experiment to any kind of food our ancestors would have encountered: game, tubers, nuts, honey, and agricultural foods such as grains and legumes. It all required effort to obtain and prepare. In affluent societies, the effort and resource cost of food are incredibly low by historical standards, due to advances in farming, food processing, and food distribution. Therefore, we eat more. It really is that simple, although there are other factors involved of course.
Did you think I was going to let Mindless Eating off the hook so easily? There are a few aspects of the book that I think could be improved. The first is Dr. Wansink's incorrect understanding of the relationship between calorie intake and body fatness, which I detailed here (2). This undermines one of the main thrusts of the book, which is that you can lose a lot of body fat simply by manipulating your surroundings into favoring a slightly lower daily calorie intake (~100 kcal). Major fat loss requires a larger calorie deficit than this.
A second problem I have with the book is that Dr. Wansink likes to spin a tale a little bit too much. The book is entertaining and accessible as a result, but there are times when the tale doesn't entirely line up with the evidence. The most obvious example of this is in the mythbusting chapter "In the Mood for Comfort Food". Here, he claims that it's a myth that comfort foods tend to be unhealthy, and it's also a myth that we tend to gravitate toward unhealthy foods when we're stressed or sad. This immediately set off my alarm bells, because I frequently cite American Psychological Association data that support these concepts-- many people do overeat unhealthy "comfort" food when stressed, as common sense would suggest (3).
The data Dr. Wansink presents in support of his "myth-busting" actually undermine his argument and support the APA data, yet he marches through them unfazed. According to the book, the top 5 most popular comfort foods, in descending order of popularity, are:
- Potato chips
- Ice cream
- Pasta or pizza
Healthy or not-- you be the judge. One important point he does make, which I agree with, is that people often eat junky comfort foods when they're happy-- not just sad.
Another thing that bothered me about the book is the frequent reliance on anecdotes and fuzzy numbers. His group has conducted countless controlled studies, so why not focus on group averages rather than individual anecdotes picked from the study population? This makes the book more engaging, but at the expense of accuracy.
One final limitation is that nearly all the studies in the book measured short-term food intake, not long-term intake or body weight changes. It's implicitly assumed that these short-term changes would translate into long-term effects on total calorie intake and body fatness, yet this isn't necessarily the case. Peoples' eating habits can sometimes adjust to new circumstances over time, and there are additional long-term homeostatic influences from the brain systems that regulate fatness.
Mindless Eating is a very thought-provoking book, full of science-backed practical information that can help us design a healthy food environment. These are important concepts, some of which are part of my core model of overweight and fat loss. With a few caveats, I think the book is a useful addition to the repertoire of anyone who's interested in understanding eating behavior and body fatness. It's also extremely accessible and entertaining.
* I own Obese Humans and Rats, and I don't think this is a great summary of it. However, the concept remains correct and important.