Most people enjoy a well-earned lie-in on the weekend, meaning their breakfast gets pushed back to brunch.
But eating meals later on Saturday and Sunday may cause weight gain – even if you consume the same amount of calories, research suggests.
Scientists found people who ate three-and-a-half hours later on weekends had BMIs 1.3 units higher, compared to those who stuck to their routine.
This remained true despite the quality of their diet, how long they slept for or how much they exercised.
Disruption to normal eating schedules can result in extra fat around the waistline because our bodies aren’t used to processing food at that time, experts say.
Eating meals later on the weekend may cause extra weight gain, even if you consume the same amount of calories, research suggests (stock)
University of Barcelona researchers, behind the study, say our biological clocks, called circadian systems, prepare the metabolism to break down food at specific times.
Cells are programmed in this way so they know when to spend energy taking up or utilising specific nutrients.
The metabolism becomes sluggish at breaking down food when it is caught off-guard by eating at different times. This seems to lead to the storage of extra fat.
HOW TO CALCULATE YOUR BODY MASS INDEX – AND WHAT IT MEANS
Body mass index (BMI) is a measure of body fat based on your weight in relation to your height.
- BMI = (weight in pounds / (height in inches x height in inches)) x 703
- BMI = (weight in kilograms / (height in meters x height in meters))
- Under 18.5: Underweight
- 18.5 – 24.9: Healthy
- 25 – 29.9: Overweight
- 30 or greater: Obese
The researchers surveyed more than 1,100 students from Spain and Mexico to come to the conclusion.
They asked participants what time they normally ate breakfast, lunch and dinner on weekdays and weekends.
Almost two-thirds ate meals an hour later on their days off and breakfast was the most delayed meal, tending to become brunch.
The study found the greater the time difference between weekday and weekend meals, the more likely the students were to be overweight.
Eating three-and-a-half hours later on weekends seemed to cause the most extreme weight gain, the equivalent of having brunch on a Saturday at 11.30am compared to breakfast on a Friday at 8am.
People who ate this late on the weekend had a BMI 1.3 units higher than participants who ate at roughly the same time on weekdays and weekends.
Dropping 1.3 BMI units is equivalent to someone who is 170cm tall and weighs 14 stone/196lbs (90kg) losing half a stone/7lbs (4kg), NewScientist reports.
Lead researcher Maria Fernanda Zerón-Rugerio said the results suggest overweight people could use meal timing as a fat loss method.
She told New Scientist: ‘Say you usually have breakfast at 7am but then on weekends you have it at 9am.
‘Your biological clock doesn’t know it’s the weekend so it’s going to prepare your body to eat at 7am, and then it gets confused when you actually eat at 9am.’
Responding to the study, Mhairi Brown a London-based nutritionist at campaign group Action on Sugar said it was an ‘interesting study’.
But she added that calorie reduction was the a proven measure that should be implemented first and foremost.
Kim Pearon, another nutritionist with her own clinic in London, said: ‘This isn’t the first study to indicate that the body thrives on eating at the same time each day.
‘Your circadian rhythm is your body’s internal clock, which dictates patterns of behaviours in organs and cells over a 24 hour period.
‘Different external cues such as light and temperature can impact our circadian rhythms, so it’s quite possible that our food intake has an impact too.’
But she said the observational study had limitations. ‘It’s less easy to account for other variables that might affect outcomes such as an individual’s weight.
‘This is summed up by the saying ‘correlation does not imply causation’ meaning that just because two circumstances coexist, it does not mean that one has necessarily caused the other.
‘When it comes to achieving and maintaining a healthy weight, what we do know for sure is that what we eat and how much is key.’
Simple calculation that shows how many calories you should REALLY eat each day to lose weight
Being in a calorie deficit is the only way to lose weight. That means you have to be burning more calories than you’re consuming.
The ideal intake can vary hugely depending on your Basal Metabolic Rate (BMR).
BMR is the amount of calories we expend just to keep our body going.
When taken into account with your activity levels it can have a huge bearing on how many calories you need to consume.
Your BMR can be found using a number of ‘macro calculators’ found online.
They take into consideration your age, work and exercise levels.
Once you calculate your BMR, you subtract around 250 calories for steady weight loss, or 500 calories for aggressive weight loss.
Additional exercise – such as a walk or run on the treadmill – can also be used as a tool to expend more calories, thus adding to your calorie deficit.
For example, a brisk half-hour walk on the treadmill may burn 250 calories.
How to calculate your Basal Metabolic Rate
10-17 years BMR = 13.4 x weight (kg) + 692
18-29 years BMR = 14.8 x weight (kg) + 487
30-59 years BMR = 8.3 x weight (kg) + 846
10-17 years BMR = 17.7 x weight (kg) + 657
18-29 years BMR = 15.1 x weight (kg) + 692
30-58 years BMR = 11.5 x w eight (kg) + 873
Once you’ve got your BMR, you need to combine it with your activity rate.
Inactive men and women: BMR x 1.4
This applies to anyone whose job isn’t physically demanding, for example, someone who mostly sits in an office at a desk all day. You don’t have any form of structured exercise in your life and if you do, it’s low intensity such as walking.
Moderately active women: BMR x 1.6
Moderately active men: BMR x 1.7
This applies to someone whose job is more physically intense or involves bein on their feet a lot. They would also take part in structure exercise of moderate intensity around three times a week.
Very active women: BMR x 1.8
Very active men: BMR x 1.9
Someone with a very physically demanding job who also does some structured exercise, or someone who does intense exercise for an hour a day.