By: Rachael Rettner
Published: 04/25/2016 11:12 AM EDT on LiveScience
Dining out or eating canned foods might not actually be so bad for your waistline, a new study from Spain suggests.
In the study, researchers at the Autonomous University of Madrid analyzed information from more than 1,600 people ages 18 to 60 who answered questions about their weight and typical eating habits, and were then followed over the next 3.5 years.
During the study, about a third of the participants (528 people) gained at least 6.5 lbs. (3 kilograms). People who said they ate while watching TV at least two times a week, or didn't plan how much to eat before they sat down to a meal, were more likely to gain weight, compared with people who didn't report engaging in these unhealthy eating behaviors.
But many other behaviors that are typically thought of as unhealthy — including eating pre-cooked or canned foods, buying snacks from a vending machine, and eating at fast food restaurants more than once a week — were not linked to weight gain.
These findings are not necessarily surprising, said Lauren Blake, a registered dietitian at The Ohio State University Wexner Medical Center, who was not involved in the study. That's because, although canned foods, fast foods and vending machine snacks can be unhealthy, there are often healthier options within those categories that people can choose, like canned vegetables or a small package of nuts from a vending machine, Blake said. And if people plan ahead before eating out, by looking at the restaurant menu ahead of time, they may be able to avoid overeating, Blake said. [Lose Weight While Dining Out: Study Reveals 6 Tips]
On the other hand, the two behaviors that were most strongly tied to weight gain — eating in front of the TV and failing to plan what to eat — both involve a lack of mindfulness during eating, Blake noted. If you're sitting in front of the TV with a bag of chips, "you're not mindful, and you don't even know how much you're eating," she said.
A greater amount of mindfulness about eating is often important for long-term weight loss, Blake said. "If we're more aware of what and how much we're eating, that's where I see people make a lot more progress with weight loss and with maintenance," she said.
But it's still hard to say from this study that certain behaviors don't lead to weight gain, said Dr. Vincent Pera, director of weight management at The Miriam Hospital in Providence, Rhode Island. Although the study took into account a number of factors that might affect weight gain — including physical activity, alcohol consumption and certain chronic diseases — there are a number of other factors that the study wasn't able to account for, such as whether people experienced periods of high stress that could have led to overeating and weight gain, Pera said.
What's more, people in the study self-reported what they ate, and how much they weighed, and it's possible that they didn't report everything that they consumed, or didn't report their weight correctly, which could affect the results, Pera said.
"Where do you draw the line in saying these certain behaviors for sure impact weight, and these don't — I think you have trouble saying that," based on these findings, Pera said.
And canned, processed and fast foods can be unhealthy even if they don't lead to weight gain. These foods are often high in salt, which is linked to a high blood pressure. Looking just at weight gain, as the study did, "doesn't encompass the whole picture of health," Blake said.
The study also found that if people engaged in five or more of these "unhealthy" eating behaviors, they were more likely to gain weight than were people who engaged in zero to two of these behaviors. This finding suggests that "interventions designed to address several [unhealthy eating behaviors] together could be more efficient" than those that target just one unhealthy eating behavior, the researchers said.
Pera said that this finding makes sense, because there are often a number of factors in people's lives and environment that affect their weight. If people get some of these factors under control, but not others, they may still gain weight, he said.
The study was published online March 31 in the journal Obesity.
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