If you’ve ever had to work out when to start and end your daily intermittent fasting period for the best results, this new study may help. Researchers have found that as long as your fast happens, it’s effective for long-term weight loss regardless of the time you clock on and off.
University of Granada scientists, in collaboration with the Granada Institute for Biomedical Research, the Public University of Navarra, and the Biomedical Research Networking Center, set out to determine if there was an optimal way to approach intermittent fasting (IF).
In a study involving 99 obese or overweight adults – split fairly evenly between men and women – participants were divided into four groups for the first part of the study. The only commonality was that they all followed the Mediterranean diet, with coaching, for 12 weeks.
There was an early fasting group (eight-hour eating window, starting before 10am), a late fasting group (eight hour eating window, starting after 1pm), a group that chose their own eight-hour eating window, and a control group that maintained a standard eating window of 12 hours or more.
After 12 weeks, the researchers assessed all participants’ fat mass and fat-free mass, and followed up with all four groups a year after the trial’s conclusion.
The study found that the eating period for those following the popular 16:8 IF program didn’t actually matter; early fasting, late fasting and self-determined fasting proved effective in the initial 12 weeks and a year on. These three fasting groups lost about 3-4 kg (6.5-9 lb) more weight than the control group.
Interestingly, though, early fasting slightly improved some metabolic measures and resulted in less subcutaneous fat (fat mass) overall. However, all eight-hour fasting schedules, on average, resulted in similar weight loss.
The researchers found that about a third of participants in the 16:8 groups continued to follow this regimen a year on from the start of the 12-week guided trial. While this may not sound particularly high, adherence is key to weight loss – and studies have shown that methods such as calorie counting through food tracking are challenging to maintain long-term.
Of course, there are limitations worth addressing here. The sample size during the trial was fairly small, which had obviously shrunk further at the one-year mark. And the researchers relied on self-reported data for physical activity and diet, so it’s unclear if the Mediterranean diet was continued. This makes it difficult to determine whether longer-term outcomes depended on continued dietary changes or IF compliance alone.
Nonetheless, earlier studies have demonstrated that IF has a favorable impact on gut hormone regulation, helping to balance appetite and dampen reward-based eating. While we don’t know with any certainty that time-restricted eating (TRE) leads to healthier food choices, the fasting window does eliminate late-night snacking – which is when processed foods are more likely to be consumed.
“To our knowledge, this is the largest and longest study examining the effects of different TRE schedules in free-living conditions and providing new insights into the long-term impact of meal timing,” the researchers write.
The study was published in the journal Clinical Nutrition.
Source: University of Granada
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