People eat more the night before a workout, a new study shows – likely because they know they’re going to work off the calories the next day.
UK sport scientists tested a group of 14 men – made up of university staff and students, as well as members of the public – who were all used to gym-based aerobic exercise.
When they had an exercise session planned for the next day, the participants ate an average of 10 per cent more, the team found.
The finding could be explained by an subconscious belief that having extra reward can be compensated for by engaging in positive, healthy behaviours, like exercise.
The study into eating behaviour and exercise found that people increase the amount of food they eat the night before a planned exercise session
This is potentially risky for our bodies as it can lead to what’s called a ‘positive energy balance’ – where our energy expenditure is outweighed by our energy intake, and we put on weight.
Interestingly, the increase in energy intake observed by the researchers was not enough to replace all the extra calories used during the exercise session.
The exercise session therefore created a ‘negative energy balance’ for the participants – where energy intake was outweighed by energy expenditure.
However, members of the public may not be so lucky if they choose to gorge on food the night before a training session.
The study was carried out by a team at the School of Sport, Exercise and Health Sciences, Loughborough University.
‘We observed around 10 per cent increase in energy intake the day before subjects planned to complete an exercise session compared to a rest control,’ said lead study author Dr Asya Barutcu.
‘So their expectation of different activity – i.e., exercise or rest – led them to eat more in anticipation of exercise.
‘However, even though they increased their energy intake by around 10 per cent in the preceding 24 hours, this was not enough to fully compensate for the energy deficit created by the exercise session.
‘So, engaging in exercise still created a short-term negative energy balance, which might be conducive for weight loss.’
The research could be crucial to help people address problems with their own eating habits and tackle an obesity crisis.
According to government figures, 20.1 per cent of children aged between 10 and 11 in England are obese and 14.2 per cent are overweight.
Worldwide obesity has nearly tripled since 1975, according to the World Health Organisation.
‘As the prevalence of overweight and obesity continues to rise globally, effective strategies to facilitate successful weight control are needed,’ the study authors say.
The testing for each trial (exercise or rest) was carried out over two days at Loughborough University.
Each participant was given breakfast (a choice of 21 items including cereal, yogurt and fruit) and lunch (24 items, including bread, ham, cheese and tinned tuna) at the university’s nutrition labs, so that their calorie intake could be monitored.
They were then given an evening food pack – containing 18 items including fruit, chocolate, crisps, and tomato pasta – to eat at home.
The following day, they returned to the nutrition lab to either rest or exercise.
The exercise trial involved 30 minutes of cycling and 30 minutes of running at moderate intensity of 75 to 80 per cent of each person’s maximum heart rate, whereas rest trial involved resting for 60 minutes.
The exercise trial involved 30 minutes of cycling and 30 minutes of running at moderate intensity (stock image)
Although the trial did not involve monitoring weight loss, Dr Barutcu said that the results could be useful for people trying to slim down.
‘If you are someone who uses exercise as a means for weight loss, then you may need to be aware of your food intake and portion size, particularly in the period before you exercise,’ she said.
‘If your food intake increases as a consequence of exercise training, before and/or after a session, then you might not see the results that you are expecting.
‘In our study, the pre-exercise energy intake was sufficient to compensate for around 45 per cent of the energy deficit created by the exercise.’
The paper has been published in the European Journal of Nutrition.
