Principal investigator Gayle Timmerman of the University of Texas at Austin says she began the small pilot study after conducting previous research on women who binge eat but don't purge. She discovered that half the binges were occurring in restaurants.
That led her to look more closely at how restaurant eating patterns might contribute to weight gain. She found that women — both dieters and binge eaters — were consuming significantly more calories and fat on the days they ate out.
"And at least in Austin, Texas, people eat out a lot. They were eating out 3 1/2 times a week. So you might be able to get away with consuming extra calories if you're eating out occasionally but if you're eating out that frequently and consuming extra calories over time, unless you're doing something to compensate, you're going to gain weight over time," she said in an interview.
Her new research, published Tuesday in the January-February issue of the Journal of Nutrition Education and Behavior, involved 35 healthy women aged 40 to 59 who eat out frequently.
Nineteen women took part in a six-week weight gain prevention intervention that included two-hour sessions each week, in groups of about eight to 10 women. The other 16 women were a control group, but had the chance to try the intervention after the study ended.
The intervention group discussed the general principles of weight management, calorie intake and strategies to use in a restaurant, including mindful eating — really slowing down to savour each bite.
"When you're going out to eat at a restaurant, you're going because you want to enjoy yourself," said Timmerman, a nurse with a PhD in the university's school of nursing.
"So how can we keep that component of going out — the pleasurable experience, and maximize that enjoyment — and yet maybe reduce or minimize the portions?"
At the beginning and end of the study, the researchers measured the women's weight and waist circumference, as well as calorie and fat intakes.
"I was really pleased because we had really good outcomes, and for six weeks, that's not a really huge long time. The women in the intervention group had lost significantly more weight than the control group. They also consumed significantly less calories and fat," said Timmerman.
At the start of the study, 69 per cent of participants were not dieting with the intention of losing weight. Most of them were overweight or obese, with an average body mass index of 31.8. But on average, the intervention group lost 1.7 kilograms during six weeks, even though the intention was weight maintenance, not weight loss. Overall, their intake of calories was reduced by about 297 calories a day.
Limitations of the study include its small sample and short duration, and the use of self-reported intake, which tends to result in under-reporting.
As for strategies that anyone can use, Timmerman said people who know they'll be eating out at dinner can budget their calories by eating less at lunch.
Participants were given information applicable to specific types of restaurants, for instance fast-food, Mexican or Italian.
A taco salad might sound healthy, Timmerman said, but it contains beef and sour cream, and the shells are fried. She found the taco salad at one restaurant contained 1,100 calories and 71 grams of fat.
When eating a salad, she suggested using a light or fat-free dressing, and dipping into the dressing on the side to get a taste with every bite, rather than pouring it all over top.
"I also really emphasize making easy substitutions, for example, black beans instead of refried beans. Instead of 300 calories with the refried beans, the same amount would be 180 calories of the black beans."
Try steamed rice instead of fried rice, or six ounces of sirloin steak (about 320 calories) instead of a porterhouse steak (about 580 calories), she said.
"Ask for the take-home box, or the to-go box, when the food comes, rather than wait till the end particularly if the portion sizes are a fairly good size," Timmerman advised. "Then pack half the food before you start so it gets it off the table, it gets it out of view because we're very susceptible."
And if you don't "love" a food, don't bother with those calories. Timmerman said she's neutral about rice that comes on Mexican food platters, and tell servers not to bring it.
Checking the calories ahead of time on a chain restaurant's website can also be helpful, and could lead to a decision to share an appetizer, for instance, rather than eat the whole thing.
On Monday, the Health Department in New York City launched a campaign urging residents to be more aware of portion sizes, and the fact that serving sizes of sugary drinks quadrupled and french fries nearly tripled in the last 50 years.
"Consuming too many calories can lead to weight gain, which greatly increases the risk of Type 2 diabetes," Health Commissioner Dr. Thomas Farley said in a statement.
"If New Yorkers cut their portions, they can cut their risk of these health problems."
Susie Langley, a registered dietitian in Toronto, said Canada so far hasn't quite caught up to the supersized portions that are frequently seen in the United States.
"If you talk to most Canadians who travel in the States, and I do myself, it seems like consumers there seem to want quantity versus quality," she said.
"Whereas especially in the city of Toronto, we have the quality versus the quantity, and some tourists will complain that portions are so small. But that's what we should be eating — smaller portions, if we want to keep our weights in line."
Restaurant-goers should stay away from deep-fried meats and fish, and skip the fries, she advised, and try to get a salad or lean meat that's been grilled or broiled.
"People always treat themselves like they're at a banquet when they eat out and they need to remember if they eat out almost every day of the week, portion control is really important."