Don’t stop thinking about tomorrow — if you want to stick to your diet. That’s the conclusion of a new study, which found that upbeat, forward-looking feelings like hopefulness led to better dietary choices, while positive emotions like happiness weren’t necessarily conducive to self-control.
“Past research is a bit conflicting in terms of how positive emotion affects food consumption,” says lead author Kelly Haws, assistant professor of marketing at Texas A&M University. “We found that the more future-focused positive emotions were leading people to consume less.”
Research on unhealthy eating behavior has typically focused on negative emotions like fear, anxiety and hopelessness because people tend to use sweet or salty foods to alleviate distress. However, as anyone who has ever been to a party knows, celebrations of good times and positive feelings are also occasions for indulgence.
Haws and her colleagues wanted to study what types of positive emotions lead to unhealthy behaviors — like letting yourself slip and have “just one” as a reward for being good — and which foster greater restraint.
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In the first experiment, 59 college students, most of whom were at a healthy weight, wrote essays aimed at making them feel either happy or hopeful. One group was asked to write about three happy experiences and to revisit the feelings they evoked. The other group wrote about and recalled the feelings associated with three experiences that made them most hopeful about the future.
While they wrote the essays, the students were given M&Ms and raisins to snack on. Both groups ate about the same amount of raisins, but those who were primed to feel happy ate 44% more M&Ms than those who were focused on their hope for the future.
“That’s huge,” says Haws. “You would not expect the effect to be that large.”
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Another experiment involving 191 undergrads found that students who generally tended to be more focused on the past were less influenced by the experience of hopefulness when it came to choosing between healthy and unhealthy snacks.
“Most people sort of implicitly understand that negative emotions can lead them to engage in unhealthy behavior,” says Haws. “With positive emotions, there’s not as much awareness about how they can have a negative effect on consumption as well.”
Recognizing this influence may help to counteract it. “A shift in the focus [toward] positive emotions [related to the] future is more conducive to achieving your goals and having more healthy behavior,” Haws says.
The study was published in the Journal of Consumer Research.
Maia Szalavitz is a health writer for TIME.com. Find her on Twitter at @maiasz. You can also continue the discussion on TIME Healthland‘s Facebook page and on Twitter at @TIMEHealthland.