Keeping portions in proportion

Most of us worry about our weight, and personal appearance is not the only reason for concern. Excess body fat has profound metabolic consequences, putting us at risk for heart disease, diabetes, stroke, cancer, and possibly depression. Nonetheless, the prevalence of obesity — a body mass index (BMI) of 30 or more — continues to rise in this country. 33% of American adults are obese, compared with 15% in the late 1970s. More than 60% of women are overweight or obese.

A number of individual variables — genetic, biological, and psychological — influence susceptibility to obesity. But they don’t fully account for America’s expanding waistline. Our genes haven’t changed. And although most of us get less exercise than we need, it’s unclear whether we’re much more sedentary than our parents were. What has changed is how we eat ... and how much we eat.

The bottom line is that we gain weight when we take in more calories than we expend. And Americans have been eating more and more. The average person consumed 300 more calories per day in 2000 than in 1985. Without a commensurate increase in physical activity, that means an added two to three pounds per month.

But why are we eating so many more calories? Experts blame increased availability of food, more eating outside the home, greater reliance on high-calorie prepackaged and fast foods, and especially larger portions. Other aspects of modern life — for example, the tendency to drive cars instead of walking and to replace active leisure pursuits with sedentary ones like television, DVD viewing, and time on the computer — prevent us from burning off these excess calories. In this “obesogenic” environment, portion control is an important strategy, along with adequate exercise, in the fight against overweight and obesity.

Eating out, eating more

Proportionally, Americans are spending almost twice as much on eating out as they did in the 1970s. In 1970, 27% of our total food budget was spent on meals taken outside the home; by 2006, that proportion had risen to 46%. Fast-food sales soared in the 1980s and 1990s, briefly overtaking full-service restaurant sales in 1997. To compete, grocery stores have expanded their convenience food sections.

Meanwhile, portion sizes in restaurant meals, take-out foods, and snacks have increased, sometimes by more than 100%. For example, a typical movie-theatre soda, once about 7 ounces, can now be “supersized” to 32 or 42 ounces. A typical bagel, once 2 to 3 ounces, now weighs 4 to 7 ounces and may contain the caloric equivalent of five or six slices of bread. Portion sizes of prepackaged and convenience foods have also expanded. (You can compare today’s portions with those of the 1980s at the National Heart, Lung, and Blood Institute’s “Portion Distortion” Web site, http://hp2010.nhlbihin.net/portion.) And practically everywhere we go — whether we’re shopping, traveling, attending a sports event, or seeing a movie — high-calorie foods (especially chips, baked goods, and soft drinks) are far more available than healthier, lower-calorie fare like salads and whole fruits

Portions and food intake

Each of us is responsible for how much we eat, but research suggests that cultural and social norms can make it hard to choose appropriate portion sizes. Also, it’s easy to confuse a portion with a serving as indicated, for example, on a package. A serving is a specific quantity of food designated on the basis of nutritional need. A portion — the amount you actually get on your plate, in the package, or at the counter — is often much bigger.

Researchers have looked into how portions affect calorie intake. Here is some of what they’ve learned:

We tend to treat a portion of food as equivalent to a nutritional serving, taking cues from our surroundings in judging the appropriate size. In one study, University of Pennsylvania scientists left a large bowl of M&Ms at the front desk of an apartment building for 10 days with a sign encouraging people to help themselves, using the scoop supplied. On some days, the scoop held one-quarter cup, on others, 1 tablespoon. Passersby consistently took just one scoop, even though they were taking twice as much on some days as they did on others. This suggests we might be satisfied with smaller portions if only bigger ones weren’t so easily available.

We’ve changed our view of which portion sizes are normal. In 2004, replicating a study first conducted in 1984, Rutgers University researchers asked college students to serve themselves typical portions of breakfast, lunch, and dinner foods from a buffet table. The students chose amounts that were not only bigger than the serving sizes on current nutritional labeling but also as much as 30% to 40% larger than those selected 20 years earlier.

Portion size can affect the amount we eat. In a Cornell University experiment, moviegoers who were served popcorn in containers holding a little over 8 cups ate 45% more than those served in containers holding half that amount. Even when the popcorn was two weeks old and recognizably stale, those using the large containers consumed 34% more. In a different study, Pennsylvania State University researchers manipulated the portions of baked ziti served as a main course at a restaurant. They used the regular portion on some days and one that was 50% larger on others. The price of the meal remained the same. Diners who were served the larger portion ate 43% more baked-ziti calories, as well as more of the accompaniments (a roll and butter and a stuffed tomato), yet surveys showed that all the customers thought their portions were equally appropriate.

Standard servings are generally much smaller than those dished out in restaurants or even at home. For example, according to the Food Guide Pyramid, a serving of pasta or rice is one-half cup — which doesn’t look like much on a plate that can hold four to six servings. The Nutrition Facts label on packaged foods lists the number of servings in the container and the calories per serving. But we don’t always read labels and may end up eating two or three servings’ worth without being aware of it.

What to do

Whether you eat out, prepare your own meals, or catch food on the run, portion control is essential to limiting your calorie intake. Here are some tips for keeping portions in proportion:

Train your eye. Measure out servings of the foods you commonly eat so you know what a single serving looks like. (For some examples, see the chart below.) Developing an eye for serving sizes can be particularly helpful when dining out or attending social events, where portions may be too large or the food unlimited.

Change your tableware. Use a smaller bowl or a mug for cereal and a smaller plate at dinner; the amount of food will look more plentiful. Instead of using a fork, try chopsticks. They can make you eat more slowly, so that your stomach has a chance to register satiety and signal the brain that it’s full.

Researchers at the University of Calgary in Canada tested specially designed portion control dishware in 130 obese patients with type 2 diabetes. Subjects were given attractive plates and bowls that were marked off in sections by food group and decorated with serving-sized food icons. The women’s diet plate provided a 650-calorie meal. After six months, the dishware users had lost more weight and required less diabetes medication than a control group given usual care.

Eat a wide variety of whole foods. Although experts don’t know the full story yet, they speculate that there are healthful synergistic effects among the many nutrients in a balanced diet. So eat a good mix of unprocessed foods — including whole grains, fruits, and vegetables (including legumes). Whole grains contain more vitamins, minerals, and fiber than refined grains. Fiber slows digestion and makes you feel full longer. The high water and fiber content of whole fruits and vegetables makes them a filling choice as well. Vegetables, fruits, and whole grains should take up at least two-thirds of your dinner plate.

Control portions at home. To discourage second helpings, serve food in the kitchen and take it to the table on plates. Try to eat at regular intervals throughout the day; if you wait until you’re hungry, you’re more likely to snack on the wrong kinds of food or overindulge at the next meal. Don’t eat out of bags or boxes; put the correct amount in a bowl or cup or on a plate. Keep healthy snacks on hand in amounts of 100 calories or less — a banana or apple; one cup of blueberries, raspberries, or grapes; or raw vegetables with tomato salsa. If you crave an occasional sweet, cut up a candy bar and keep the pieces in the freezer; have only one “serving” at a time and let it slowly melt in your mouth.

Control portions while eating out. Go to restaurants that offer plenty of à la carte options; avoid buffets and salad bars. Instead of a dinner, order a low-fat appetizer and a large salad with dressing on the side. Ask to substitute fruits, vegetables, or a salad for French fries. Arrange with a dinner companion to split an entrée, or eat only half of the portion and take the rest home. At a cocktail party, instead of constantly grazing, allot yourself a few items, put them on a small plate, and don’t take any more.

Borrow from mindfulness practices. Mindfulness means giving your full attention to the present. Try to bring all your senses to the experience of eating, including your surroundings. Take time to savor the texture, flavor, and aroma of your food. After taking a bite, put down your fork and chew slowly. These steps can help slow your eating and give your brain a chance to receive the message that your stomach is full. And when it gets that message, stop eating.

Harvard Women’s Health Watch

Volume 15 – Number 3 – November 2007