Exercise variety promotes healthy eating

Researchers have found evidence that more choice during exercise results in healthier eating after exercise. This finding highlights how both behaviours are connected and how we may use this information to our advantage.

The role exercise plays in keeping us healthy is complex. A prime example of this is found in exercise programs for weight loss. When it comes to weight loss, exercise is not always as effective as we may hope.

One reason for this is may be due to post-exercise eating. This can be highly variable; on some occasions, exercise helps motivate healthy eating, but on others, exercise can be a licence to indulge.

Researchers from The University of Western Australia have shed some light on the link between exercise and diet. Publishing in Medicine and Science in Sport and Exercise, they demonstrate that the participants' sense of choice in an exercise session affected the type of food eaten afterwards when presented with a breakfast buffet.

Participants were randomised to either a ‘choice’ or ‘no-choice’ group. The choice group could choose details about their exercise session such as the type of exercise, the duration, the intensity, the time and even the radio station playing in the background. Every lucky participant in this choice group was paired to a participant in the no-choice group with none of these options.

The matching pairs were similar in many respects. They were the same gender, a similar height, weight, level of fitness and importantly they expended a similar amount of energy in their respective exercise sessions. The difference was that one group had choice and the other group were told what to do.

However, the clever part of the experiment was that the true nature of the study was only disclosed to participants after they had their fill at the breakfast buffet. As participants tucked into their food they were not aware that what they were eating was being secretly measured. Lead author Natalya Beer explained, “When we presented the food buffet to them we actually said it was a thank you gesture”.

The researchers even confirmed the participants' ignorance with what is known as a ‘suspicion probe’. It’s not as sinister as it sounds; it was a questionnaire asking the participants what they thought the purpose of the study was. This was important to make sure participants weren't self-conscious about the food they were eating.

The results showed that those participants who were deprived of choice had an energy intake that was about 30% higher than the picky participants in the choice group. Furthermore, the choice deprived participants ate more ‘unhealthy type’ foods.

So what could be going on here? The researchers hypothesised that perhaps being deprived of choice meant more willpower was required to complete the exercise session. Therefore, there was less willpower available when participants were deciding whether or not to have that extra muffin at the breakfast buffet. This is called ‘ego-depletion’.

There is a theory that ego-depletion is accompanied by lowered glucose levels but the researchers measured glucose levels and found no difference between groups. Uncovering the biological mechanism responsible remains an important question for this field.

However, there is still a lesson to be learned. As Natalya put it, “It seems that simple acts of providing choice in an exercise session, if they can influence the way we behave in a positive way after exercise, then why not incorporate those aspects; it’s an important consideration for those who exercise themselves to get the most out of exercise but also for people motivating others to exercise”.