Perceptions of Calories "Burned" and Post-Exercise Energy Intake

Have you ever felt the urge to reward yourself with food after a workout? Many do.

Some might be choosing their food choices off how many calories were "burned" during their workout. For some, being able to eat what they want is a reason they exercise in the first place. Clearly, such a mentality is in opposition to the goal of healthy eating.

We have already discussed the conflicting caloric estimations of cardio machines. In other words, some might be eating more, because they "burned" so many calories, only to find out that the cardio machine's estimation of calories was bogus. Oops.

License to Eat?

Another interesting twist, which is of interest here, is the idea that if we believe we expended more energy (in calories), does that give us the license to eat more? This is exactly what a group of researchers from the University of Bristol looked at in a recent study:

Licence to eat: information on energy expended during exercise affects subsequent energy intake

In short, they asked 70 men and women to complete an exercise bout on a stationary bike. Some were told they expended 265 calories, while others were told they expended only 50 calories.

Unbeknownst to the participants, they actually expended 120 calories during their exercise.

After exercise, they were presented with orange juice, tortilla chips, and chocolate chip cookies. They tasted each, and rated how much they liked them. They then had 15-minutes in which they could eat the rest.

As shown in this figure, those who were told they expended 265 calories during exercise ate 67 calories more of cookies than the group who were told they expended only 50 calories.

67 calories of cookies is not a huge effect, but could still lead to changes in body weight over time. So, the researchers looked further into the results.

They tentatively found that those were had the least amount of dietary restraint over their food intake consumed 128 calories more cookies when told they expended more calories from exercise.

Take Home Message?

If these results hold true to the general population,

• People might be eating more calories, mainly from sweets and other high calorie foods, following exercise where they believe they "burned" more calories.

In other words, how much we eat after exercise might not be simply due to how much energy we actually expend following exercise, but our perception of how much energy we expended.

We should be careful not to do this, especially since calorie estimation from cardio machines and our fitness trackers can be fraught with errors.

• The effect might be stronger in those with lower levels of dietary restraint, where they eat much more when they believe they "burned" more calories.

For example, how would you answer this question, from 1 (never) to 5 (very often)?

"Do you try to eat less at mealtimes than you would like to eat?"

If you answered lower on this question (1 or 2), you could be low on the dietary restraint scale used in this study.

Such individuals might need to be even more cautious of their eating behavior after exercise - hopefully choosing healthier options, and not feeling they have "license to eat" whatever they want.

We should also be aware of our eating of 'fitness' foods, because of what it says on the label (e.g. 'low-fat').

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References

McCaig, D. C., Hawkins, L. A., & Rogers, P. J. (2016). Licence to eat: Information on energy expended during exercise affects subsequent energy intake. Appetite, 107, 323-329.