Intermittent fasting is often seen as a straightforward concept: eat less over certain periods to boost metabolism. However, a new study indicates that some types of intermittent fasting might not significantly impact metabolic or cardiovascular health markers.
Led by researchers at the German Institute of Human Nutrition Potsdam-Rehbruecke (DIfE), the study involved 31 overweight or obese women who followed two distinct intermittent fasting schedules for two weeks each. These schedules spanned 8 am to 4 pm and 1 pm to 9 pm, representing a type of intermittent fasting called time-restricted eating (TRE).
Despite the different timings, the diet parameters remained constant. Participants were allowed to eat as they usually would, thus consuming the same total caloric intake — making this an isocaloric study.
Interestingly, while the women did manage to lose some weight, other expected benefits — such as reduced blood sugar, lower blood pressure, and decreased cholesterol — were absent from the findings. This has cast some doubt on the efficacy of these timed fasting approaches.
The researchers noted that “the beneficial cardiometabolic effects described previously might be induced by TRE-mediated calorie restriction and not by the shortening of the eating window itself.” They stated, “In this nearly isocaloric trial, no improvements in metabolic parameters were observed after two weeks of TRE.”
The results hint that it might be the reduction in calories rather than the timing of meals that could positively affect health indicators, although it’s good to remember this was a short-term, small-scale study.
On top of the slight weight loss, the study also revealed that participants’ body clocks were affected, with shifts in their circadian rhythms — including those linked to sleep — in accordance with the TRE schedule.
This adds more evidence that our internal clocks can be influenced by our eating and drinking times, alongside other factors such as the setting of the sun. This could have implications for health issues related to late-night eating.
Olga Ramich, a biologist and nutritionist at DIfE, mentioned that people aiming to lose weight or enhance their metabolism should consider both the timing and their overall energy balance.
Boosting metabolic health is critical, especially concerning insulin resistance and diabetes. Future research could potentially reshape dietary recommendations for individuals dealing with these conditions or those at risk.
The researchers are eager to delve deeper into how calorie intake relates to timing. There’s a chance that in situations with restricted calories, the timing may play a role in health markers.
Different varieties of intermittent fasting are still under the microscope, although studies can vary widely in terms of allowed diets, participant demographics, duration, and the health outcomes measured.
They concluded that their findings underscore the significance of calorie restriction for metabolic improvements within TRE. Future studies need to address whether meal timing under calorie-restricted conditions can further affect metabolic changes, and if optimal eating times differ among individuals.
The research appears in Science Translational Medicine.
