By ANAHAD O'CONNOR New York Times
Researchers have discovered that you are more likely to crave bread and other carbohydrates when you are hungry.
Have a habit of skipping meals? A new study shows that people who sit down to eat after an overnight fast are more likely to ignore protein, fats and vegetables and head straight for high-calorie carbohydrates and starches first.
The news may not come as a surprise to long-term dieters, or anyone used to bingeing on pasta or potato chips on an empty stomach. But the study also revealed some telling details about food choices and the order in which we eat different kinds of foods. When given the opportunity to eat a salad and a plate of French fries, for example, people who started with the starchy food downed significantly more calories per meal than those who did the reverse.
The findings have implications for people who regularly miss meals, whether because of hectic schedules or for the deliberate purpose of losing weight. Nationwide, about 15 percent of adults say they have fasted to slim down, and a number of popular diets encourage intermittent fasting.
“I think this emphasizes the importance of controlling your environment as far as the types of foods you’re exposed to when you’re hungry and how much of them you can get,” said Aner Tal, a postdoctoral research associate in the Food and Brand Lab at Cornell and lead author of the study, published in Archives of Internal Medicine. “Because otherwise, you will mindlessly choose foods that are less healthy for you.”
Dr. Tal and his colleagues knew from previous research that hunger influences food choices. After skipping a meal or two, people naturally consume more calories than they otherwise would when finally given the opportunity to eat. Studies have also shown that high-calorie foods stimulate greater activity in reward centers of the brain when people eat them after missing breakfast.
But the researchers wanted to know whether hunger, in addition to causing greater caloric intake, would also cause people to gravitate toward certain types of foods when given an array of choices. To find out, they recruited 128 Cornell students, who were assigned to one of two groups. One group was told to fast for 18 hours — starting at 6 p.m. — and then to show up the next day for a buffet-style lunch. The second bunch of students, serving as the control group, did not fast the night before.
“We didn’t want to do anything too extreme,” Dr. Tal said. “People don’t normally go for fasts that last for days. But I’ve had a lot of days where I was busy and didn’t really eat anything until the evening, so my last meal was the previous night. We thought this would have greater applicability to people’s day-to-day lives.”
Over the course of 12 weekday lunches, the researchers studied the students as they arrived at the lunch table. The subjects had their pick of starches, including dinner rolls and fries, as well as vegetables, beverages and proteins like chicken and cheese. To prevent the foods’ placement from influencing the results, the researchers rearranged the items at each meal. They also measured the amounts the subjects served themselves, using scales embedded in the tables.
Those in the group that had fasted, it turned out, were more likely to begin their meals with starches, eating the bread or French fries before anything else about a third of the time, compared with just over 10 percent of the time with the control group. Those who fasted were also less likely to eat vegetables first. Only a quarter of them did so, compared with about half of the people in the control group.
“Importantly,” the researchers wrote, “starting their meal with a particular food led all participants to consume 46.7 percent more calories of it” compared with other foods. They also found that people who chose not to eat the vegetables first consumed about 20 percent less of them. Those who went straight for the starches ultimately ate about 20 percent more calories over all than their peers.
“This shows that what you choose first is important when it comes to how much you ultimately eat,” Dr. Tal said.
He speculated that hunger sets off a desire for carbohydrates because of the body’s tendency to maximize efficiency. “It’s a quicker, higher-energy source,” he said. “You’re essentially maximizing calories per time, so you replenish your deficit faster.”
For regular dieters and people who frequently find themselves ravenous after missing meals, Dr. Tal said the lesson is to keep high-calorie foods out of reach, or at least make them less visible in the pantry or kitchen cabinets. But he also pointed out that the findings could be useful to hospitals looking to provide better nutritional options to food-deprived patients, since fasting is often a requisite before operations and other medical procedures. Vegetables, salads and fruit should be made more visible and convenient in cafeterias, he said, and hospitals could reduce serving sizes of starches like pasta and mashed potatoes, “or offer them in combo meals that balance the amount of starches with protein and vegetables.”