Eating your last meal for the day at 2 pm may sound like torture – but it may help you lose weight.
Scientists found fasting with a six-hour eating window starting at 8 am can suppress the appetite and lower levels of hunger hormones.
Fasting diets have previously been thought to help people shed the pounds by way helping them burn more calories.
However, the study suggests restricting meal times helps people to simply eat less, and it may be due to eating in line with the natural body clock.
Although experts have long argued it’s not what you eat, when, researchers said this is the first time a study has shown how meal times affect metabolism.
The study at the University of Alabama at Birmingham tested Early Time-Restricted Feeding (eTRF), which is a type of fasting where dinner is eaten in the afternoon.
Researchers enrolled 11 men and women who needed to lose weight, aged between 20 to 45 with a BMI between 25 and 35.
Participants tried two different meal timing strategies, one where they ate three meals over 12 hours, between 8 am and 8 pm.
The other strategy saw them have only six hours to eat three meals, between 8 am and 2 pm.
The same amounts and types of foods were consumed on both schedules which the participants carried out for four days in a row.
On the fourth day, researchers measured the metabolism of participants by placing them in a respiratory chamber.
This allowed them to see how many calories, carbohydrates, fat, and protein were burned by each of the volunteers.
Researchers also measured the appetite levels of participants every three hours while they were awake, as well as hunger hormones in the morning and evening.
They discovered the six-hour eating window improved the ability to switch between burning their food for energy to burning fat.
It also increased fat-burning, the researchers led by Dr. Courtney Peterson reported in the journal Obesity.
The six-hour eating window also helped lower levels of the hunger hormone ghrelin, which stimulates the appetite.
The researchers said eating earlier in the day syncs with circadian rhythms – the body’s internal body clock.
Eating all meals between 8 am and 2 pm may help to lose weight as scientists at the University of Alabama Birmingham show fasting diets can suppress the appetite
Circadian rhythms determine the body’s hormones and metabolism, relating to hunger, tiredness, and mood, based on exposure to sunlight.
Co-author Dr. Eric Ravussin said coordinating meals with circadian rhythms ‘may be a powerful strategy for reducing appetite’.
Dr. Peterson added: ‘We suspect a majority of people may find meal timing strategies helpful for losing weight or to maintain their weight.’
She said this is because these strategies naturally appear to curb appetite, which may help people eat less.
Dr. Peterson added: ‘Whether these strategies help people lose body fat need to be tested and confirmed in a much longer study.’
The use of fasting diets for health are heavily disputed. Yesterday, scientists said teenagers who skipped breakfast were more likely to have a high BMI.
Advocates swear by fasting diets for reducing stress, improving energy, protecting against type 2 diabetes and reducing weight.
Previously, research on the topic was conflicted on whether meal timing strategies helped with weight loss by burning more calories or by lowering appetite.
This study did not test other fasting methods, including the popular 5:2, which is fasting for two days on 500 calories and eating healthily but normally for five.
Nor did it test the 16:8, which restricts eating to midday to 8 pm, with a 16-hour fasting window overnight.
However, Dr. Peterson said: ‘We think that the appetite lowering and fat burning effect would likely also apply if the eating window is somewhat later in the day, such as 12 pm to 6 pm or 11 am to 7 pm, but probably not if the eating window were late at night.
‘We think that our results would apply to a majority of people, even if they get up later in the morning.
‘A six-hour eating window may be too challenging for the average person, and data we have from other studies suggest that eating in an eight or ten-hour eating window up to six days per week is a more realistic target.’
But researchers have previously found that eating between 8 am and 2 pm, followed by an 18-hour daily fast kept appetite levels more even throughout the day, in comparison to eating between 8 am and 8 pm.
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