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Just Thinking About Exercise

The best way to lose weight and maintain that weight loss? Eat right and exercise. There's been a lot of research on ways to help people make the effort to make changes in their diet and exercise behaviors, but recently Dr. Brian Wansink and colleagues from New Mexico and France noted that little research has been done on how exercising may actually mean eating more afterward - to compensate for the calories burned.

In devising a research strategy, they also noted that other research suggests that people believe that participating in positive (healthy) behaviors can serve to offset the effects of negative (unhealthy) behaviors later. (Makes sense: how often have you thought something to the effect of, "I'll take this long walk so I can have ice cream later.")

Even further, Wansink and his colleagues theorized that just thinking about exercise - not actually doing any - could affect how much food a person served themselves afterwards (Appetite 2011;56(2):332-335).

They performed a survey at a shopping mall to test their theory. Participants were told that the survey was about shopping habits and attitudes and offered snacks afterwards as compensation for answering the survey questions. A total of 94 men and women between the ages of 19 and 67 answered questions about their shopping behavior, then were randomly assigned to one of three lines of questioning:

Exercise Condition: these participants answered questions about how much they exercised, what they did, and when they exercised. They were then asked to read a brief essay describing a 30-minute walk during which they focused on the exercise and how tired they felt.

Fun Condition: these participants answered questions about their music preferences, whether they owned an MP3 player, the quality of music on an MP3 player, and whether they owned an iPod. They then read an essay describing a 30-minute walk during which they focused on how much they enjoyed listening to the music on their MP3 player.

Control Condition: these participants did not read any essay, but skipped to the next section of the study.

In the final portion of the study the participants answered a few more questions regarding their height, weight, age and level of hunger, then were offered one of two snacks (M&Ms or Chex Mix) which they could serve themselves into ziplock bags. After serving themselves, the research assistants weighed the bags while the participant answered a few more questions, including estimating how many calories were in the snacks they had served themselves.

After comparing how many calories in snacks each participant had served themselves with which condition they had been assigned, the researchers found that regardless of whether the exercise was presented as tiring (the Exercise Condition) or fun, those who thought about exercising served themselves at least 40% more calories than those who simply served themselves some snacks. Of those who estimated the number of calories they had served themselves, those who thought about exercise were somewhat less likely to be able to accurately estimate how many calories they had put in their snack bags.

What this means for you

If just thinking about exercise makes you want to eat more and makes you less able to accurately estimate calories (as this research suggests), portion size becomes more important. Stick to fruit - especially those with that oh-so-convenient single serving size such as apples, bananas or oranges - or a single handful of nuts as a snack.

First posted: February 23, 2011