A lot of factors likely affect how much food you eat, such as how it looks and smells, how tasty it is, how filling you believe the food will be and whether you were taught to “clean your plate” when you were young. Environmental influences, such as the size of food packages, how much food you’re served and social norms, can also have a big impact.
People often eat more food when offered larger-sized portions, packages or tableware (such as plates or bowls) than when offered smaller-sized versions. The same goes for beverages. That was the not-so-surprising conclusion of a rigorous, systematic review of 72 randomized, controlled trials on portion control. The review was recently published by The Cochrane Collaboration, an independent group of researchers, health professionals and other experts.
“We usually don’t monitor exactly how much we eat or drink, so external factors such as the amount on our plate or how long we sit at a table can have a major influence on total calorie intake,” says Alice H. Lichtenstein, DSc, director of Tufts’ HNRCA Cardiovascular Nutrition Laboratory. “When these behaviors lead to weight gain, the risk for type 2 diabetes, cardiovascular disease and certain cancers increases dramatically. To prevent this situation it is important to become more mindful of our eating habits.”
Portion sizes (and waistlines) have increased substantially over the past few decades. For example, a typical muffin in the United States is 333% bigger than the USDA standard size, and a serving of pasta is 480% larger. Here’s the concern: The more we’re exposed to large portions, the more we may start to view them as normal and appropriate.
A distorted view of appropriate portions was found in a study recently published in the journal Appetite. Researchers tested the impact of showing college students photos of different-sized portions of entrees and snack chips. In all three cases, participants who viewed photos of larger portions of food, as opposed to smaller portions, said that a normal portion of food would be larger than a moderately-sized one they were shown in a photo.
“Some food companies are starting to offer much smaller sizes, such as mini 7.5-ounce cans of soda,” says Robin Kanarek, PhD, a psychology professor researching nutrition and behavior in Tufts’ School of Arts and Sciences. “We don’t yet know what the long-term consequences of that will be.” One potential risk is that you might buy (and therefore, consume) even more if the calories are less per container or if it’s a better value to buy a bigger package of several smaller servings.
Portion Size Norms:
“There’s a tendency to think that the amount of food you’re served is the amount you should eat,” Kanarek says. “For example, if you’re served a sandwich made with two pieces of bread, you’re likely to eat the whole thing. But you could easily remove the top slice of bread and eat an open-face sandwich or eat half of the sandwich.”
A recent study published in Health Psychology found that people tend to integrate information about the overall portion size and the number of individual units in the portion to help them determine how much to eat. In the study, participants were offered either one 60-gram cookie or three smaller 20-gram cookies. People ate less overall when offered three smaller cookies rather than one larger cookie, although the overall portions offered were the same.
“We don’t yet understand all of the determinants for how much someone eats at any one time,” Lichtenstein says. “In addition to the factors already noted, other variables include how many items are part of the meal, whether the food is pre-served or determined by the diner, how much time you have to eat, whether you are eating with others or alone and whether you have a digital device in your free hand and are focusing on things other than your food.” When you are aware of such factors you’re more likely to manipulate them to your advantage.
Outsmart Your Plate:
“Use small plates,” Kanarek advises. “Research suggests that can help you take less food and eat less.” This was confirmed in a recent review of the evidence on plate and bowl size published in the Journal of the Association for Consumer Research.
Researchers analyzed 56 studies on dinnerware size and found that, overall, reducing plate size by half decreased the amount of food people ate by 29%, on average. But doubling the size of plates increased the amount of food people served themselves or consumed by 41%. However, this only seems to hold true when you serve yourself, such as from a buffet or at home.
What doesn’t seem to make a difference in how much you eat is if someone else serves your usual portion on a smaller plate. You’ll likely eat the same amount as usual.
Although you may feel like it will be tough to “trick” yourself into taking a smaller portion if you’re aware of using a smaller plate, researchers say there’s already some evidence suggesting that over time you tend to forget about the plate change. Essentially you’ll be reversing the creeping portion sizes that have accompanied increasing plate sizes the past few decades.
Make Portion Control a Habit:
When you’ve had a stressful day or you simply have a lot of distractions and your willpower is waning, having healthy habits in place may mean the difference between limiting food portions or overindulging in a box of bon bons.
Researchers at the University of Southern California (USC) found this to be true in a study of 59 self-confessed chocolate lovers. The study participants were randomly assigned to participate in a computerized activity that repeatedly simulated consuming or rejecting chocolates. Next, they were asked to watch a funny video, but half of them were instructed to avoid showing facial expressions during the activity, which was verified to be a tiring task. Lastly, they were asked to taste test chocolate candy, although the real purpose was to determine how much they would eat.
Researchers found that participants who were trained to reject chocolate ate significantly less chocolate when their self-control resources were depleted (by the video activity) compared to those who weren’t trained to reject chocolate.
“We all have habits about what and how much we eat. These habits come to mind automatically when we eat in the same contexts as in the past,” says Wendy Wood, PhD, a psychology professor at USC and one of the authors of the study published in Appetite. “We usually just carry out the behavior that we’re used to.”
One way to break a habit of over-sizing portions is to form a new, smaller-sizing habit. Wood suggests you “figure out the easiest way to limit portion size: buy pre-packaged portions, prepare food ahead of time or share large menu items. Essentially, you want your environment to do the work. Find ways to have smaller portions easily available. Over time, small portions will become a habit.”
Lastly, realize that portion control is most relevant when eating calorie-dense and less healthy foods. Not many scientists would advise against a large portion of broccoli or celery.
Smart Portion Control Strategies:
– Use smaller plates, bowls and serving spoons. A plate 9 inches in diameter is appropriate for lunch and dinner.
– Avoid eating straight from the package. If you’re dipping directly into a box or bag, you won’t know how much you’ve eaten.
– For foods you eat regularly, such as cold cereal or nuts, keep an inexpensive measuring cup or measuring spoon in or with the container so you can easily dish up an appropriate portion.
– At a restaurant, choose the smallest size available. If meals are oversized, put half in a to-go box as soon as you get your food or plan in advance to split your dish with a friend.
– At home, dish up a single serving at mealtime and leave extra portions in the kitchen. For snacks, fill reusable containers with single-serve portions from a bigger package.
– Look for recipes that include nutrition information and the number of servings. To analyze your own recipes, visit <supertracker.usda.gov/myrecipe.aspx>.
– Especially watch portion sizes of starch- or sugar-rich foods, such as white bread, white rice, crackers, sweets, soda, sports drinks and fruit juice, as well as alcohol, which are all easy to overdo and linked to weight gain.
– Opt for nutrient-rich, minimally processed foods, such as whole fruits, non-starchy vegetables, legumes (beans), nuts and unsweetened lowfat or nonfat yogurt, which can more naturally help fill you up and help you manage your weight.
➧ Learn the right portions for you based on your individual needs with the MyPlate Daily Checklist at <choosemyplate.gov/myplate-daily-checklist>.
TO LEARN MORE: Cochrane Database of Systematic Reviews, September 2015 –
TO LEARN MORE: Appetite, March 2016 –
TO LEARN MORE: Health Psychology, June 2015 –
TO LEARN MORE: Appetite, August 2016 –