People who exercise increase their meal size by a quarter when planning food in advance

a woman sitting at a table writing on meal planner sheets, there is a selection of vegetables and fruit spread out

Gym-goers who pre-plan their meals in advance of aerobic exercise increase their portion size by a quarter on days that they exercise, a new study has found.

Researchers at Loughborough University wanted to know why many chronic exercise intervention studies – which investigate the effect of exercise training on weight management - were not seeing the expected amounts of weight loss.

And whether anticipation of exercise altered people’s planned food intake.

The team devised two hypothetical scenarios for participants to plan meals for – one where they were resting and one where they were exercising.

They found that in the exercise scenario, participants increased their planned energy intake by about 24%, on average, compared to the rest scenario.

This means that instead of burning an extra 500 calories from this exercise, it’d be as if they burnt 350 calories, as they consumed 150 calories in anticipation already.

Lead author Asya Barutcu said: “The overall purpose of this project was to try and find some answers to the reason behind why the chronic exercise intervention studies are not seeing the expected amounts of weight reduction.

“Most of the research that investigated the effects of exercise on energy intake and appetite, focussed in the post-exercise period.

“But when findings from the acute studies are applied to the chronic studies, researchers or participants are not seeing the expected results.

“So, this meant there has to be a compensatory behaviour taking place.

“Our findings suggest that, when people know they have an exercise session coming up, they will plan to eat more food for afterwards, if they are planning this meal beforehand.”

Forty regular exercisers took part in the study, Anticipation of aerobic exercise increases planned energy intake for a post-exercise meal, which has been published in the journal, Appetite.

For each scenario, subjects had to plan their lunch by serving themselves cheesy tomato pasta and chocolate buttons.

Exercise increased the total amount of food served by an average of 24% – which was, 25% more pasta and 20% more chocolate.

Asya said: “Our purpose was to understand any compensatory behaviour related to meal planning that takes place in anticipation of exercise.

“Planning of meals and snacks is an important component of energy intake that has not been explored in the context of exercise.

“If we know how exercise might influence this behaviour, we may be able to help those seeking to lose weight eliminate it by consciously reducing energy intake or making different food choices.

“From a weight loss point of view, increasing awareness of this behaviour might go a long way.

“It should also be noted that this is just one study, and although we have a couple more studies ongoing on this subject, care should be taken when applying these findings for the whole population.”