Restricting your eating to a shorter window won’t boost your metabolic or heart health if you’re still eating the same number of calories, scientists have warned dieters.
New research from the German Institute of Human Nutrition Potsdam-Rehbrücke and Charité-Universitätsmedizin Berlin suggests the health improvements people have seen in earlier studies were probably down to accidentally eating less food, rather than the timing itself.
The study, led by Professor Olga Ramich and published in Science Translational Medicine, recruited 31 women with overweight or obesity and had them follow two different eating patterns, each lasting a fortnight.
One schedule meant eating between 8am and 4pm, while the other pushed meals to between 1pm and 9pm, with participants required to eat nearly identical meals with the same calories and nutrients throughout both phases.
Meal timing did have one notable effect in the study
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The team is collecting blood samples across four clinic visits, running glucose tolerance tests, and monitoring blood sugar levels around the clock. Motion sensors were used to keep tabs on physical activity.
But despite careful tracking, the results showed no meaningful changes in insulin sensitivity, blood sugar, cholesterol, or inflammation markers after the two-week periods. Meal timing did have one notable effect.
Analysis of blood cells revealed that participants’ internal body clocks shifted by roughly 40 minutes when they followed the later eating schedule compared to the earlier one.
Those eating later also tended to go to bed and wake up later.
“The timing of food intake acts as a cue for our biological rhythms — similar to light,” said first author Beeke Peters.
What does this mean for those hoping to shed a few pounds or improve their health?
“Our results suggest that the health benefits observed in earlier studies were likely due to unintended calorie reduction, rather than the shortened eating period itself,” explained Prof Ramich. In other words, it’s not just about when you eat — it’s about how much.
This comes after research published last September raised eyebrows about restricted eating windows altogether.
Those who want to lose weight have been advised to track their energy balance
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That study tracked more than 19,000 American adults over eight years and found those who squeezed their meals into under eight hours faced a 135 per cent higher risk of dying from heart-related causes compared to people spreading their food across 12 to 14 hours.
“Those who want to lose weight or improve their metabolism should pay attention not only to the clock, but also to their energy balance,” Ramich concluded.
Future research will look at whether combining time-restricted eating with actually cutting calories might deliver stronger results.
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