An interesting new clinical study is suggesting restricting food intake to a 10-hour window each day may be a simple yet beneficial way to help treat metabolic syndromes such as diabetes or heart disease. The 12-week pilot study revealed the eating intervention, in conjunction with prescribed medicines, improved patients’ health outcomes.
One of the more fascinating dietary fashions to arise in recent times is known as time-restricted eating (TRE). Instead of interspersing whole days of fasting across a week or month, this eating strategy looks to limit your caloric intake to short windows of time in a given 24-hour period. Generally, TRE methods suggest only eating between four and eight hours a day, meaning a fasting stretch of 16 to 20 hours.
One of the theories underpinning these dietary strategies is that restricting eating to a limited time window better synchronizes a person’s caloric intake with their circadian rhythms. Epidemiological studies have found a majority of people spread their food intake over at least 15 hours a day.
As little as 10 percent of people compress all their meals into a 12-hour-or-less stretch each day. While some research is building to suggest health benefits to only eating in four- to eight-hour windows, this new study set out to find out whether a 10-hour eating window could be just as beneficial.
“There has been a lot of discussion about intermittent fasting and what time window people should eat within to get the benefits of this kind of diet,” explains Satchidananda Panda, co-corresponding author on the new study. “Based on what we’ve observed in mice, a 10-hour time window seems to convey these benefits. At the same time, it’s not so restrictive that people can’t follow it long-term.”
To test the eating strategy on human subjects a team of researchers from the Salk Institute and the University of California, San Diego, conducted a small pilot study. They recruited 19 subjects, most classified as obese and receiving pharmacological treatment for a diagnosed metabolic condition. All subjects self-reported prior eating patterns spanning at least 14 hours a day.
The intervention tested was incredibly simple. Subjects were directed to continue regular diets and exercise but simply compress any caloric intake to a 10-hour window each day, essentially letting their bodies fast for 14 hours across every 24-hour cycle.
For such a small and simple intervention the results were somewhat impressive, with an average three to four percent reduction in body weight and body mass index seen across the entire cohort after three months. Alongside self-reported improvements to general energy levels and sleep quality, the cohort displayed reductions in cholesterol levels and blood pressure at the end of the 12-week trial.
“We told people that they could choose when they ate their meals, as long as they remained within the 10-hour window,” says Panda. “We found that universally, they chose to eat breakfast later, about two hours after waking, and to eat dinner earlier, about three hours before going to bed.”
The researchers behind the new study are well-aware of the numerous limitations behind such a small trial. Most notably the trial did not include a control group which makes it certainly difficult to clearly correlate the final result with the studied eating intervention. Duane Mellor, from Aston University, points out the lack of control isn’t the only problem with this particular study.
“In the case of this study there are lots of limitations, not just the lack of a control group – a key one being that the act of recording food intake has been shown in other studies to reduce calorie intake and help with weight loss,” says Mellor, who did not work on this new study. “Also, although lots of tests were done on the participants, it seems unclear how they justify the conclusion that improvements were seen independent of weight change as there simply was not a big enough number of people to make this assessment.”
So, were the beneficial effects seen in this study directly related to the TRE strategy? Or were the health improvements more a reflection of the diet indirectly lowering overall caloric intake and making the cohort more aware of their eating patterns?
“It’s possible to over speculate that time-restricted eating is a magic bullet to health whereas it may be that it’s just though calorie restriction,” suggests Jenna Macciochi, an immunologist from the University of Sussex. “On the flip side, for people who are struggling with fad diets it may be a useful tool and help compliance.”