December 05, 2019
"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," co-corresponding author Satchidananda Panda, PhD, said in a statement.
"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," added Panda, of the Salk Institute for Biological Studies, La Jolla, California. Panda is the author of the book The Circadian Code and collects royalties.
The study was published online December 5 in Cell Metabolism by Michael J. Wilkinson, MD, of the University of California, San Diego, and colleagues.
Because most of the women were taking a statin, antihypertensive medications, or both at study entry, "the observed benefits of time-restricted eating were additive to the effects of these medications ... and in this population at high risk for cardiovascular disease, a significant reduction in atherogenic lipids, blood pressure, and blood glucose on top of medical therapy has important clinical implications," say the investigators.
Participants Lost 3% of Body Weight in 12 Weeks
In the study, 19 women with metabolic syndrome were instructed to restrict food consumption to 10 hours a day for 12 weeks, creating a 14-hour fast each night.
Importantly, they were not told to reduce their caloric intake or change their diet in any way during the 10-hour time-restricted eating window, the investigators point out.
Most of the women were obese, with an average body mass index (BMI) of 33 kg/m2.
"Participants used a validated app — myCircadianClock (mCC) — to log their caloric intake during the 2-week baseline and 12-week intervention periods," they explain.
Over the 12 weeks of the study, participants lost 3.3 kg, or approximately 3% of their body weight, relative to baseline (P = .00028), the investigators report.
This change led to an approximately 3% reduction in BMI (P = .0001), as well as about a 3% reduction in body fat (P = .0001), including a significant 3% reduction in visceral fat (P = .004) and a 4% reduction in waist circumference (P = .009), the authors note.
Interestingly, the amount of weight participants lost during the study was comparable to that achieved by restricting calories and increasing exercise, the researchers point out.
Cardiometabolic Parameters Improved
The time-restricted eating strategy also had a number of favorable effects on cardiometabolic parameters.
For example, there were significant reductions in total cholesterol, low-density lipoprotein (LDL) cholesterol, and non-high density lipoprotein (non-HDL) cholesterol, none of which were attributable to weight loss.
There were also significant reductions in systolic and diastolic blood pressure, and among those with elevated fasting glucose levels at baseline, there was a significant reduction in A1c.
These improvements in cardiometabolic parameters were observed independent of any change in physical activity and were again independent of weight loss, the authors emphasize.
Table. Change From Baseline in Endpoints in Intermittent Fasting Group
|Endpoint||Mean Change (Percentage Reduction)||P value|
|Total cholesterol, mg/dL (%)||–13.1 (11)||.03|
|LDL cholesterol, mg/dL (%)||–11.9 (11)||.016|
|Non-HDL cholesterol, mg/dL (%)||–11.6 (9)||.04|
|Systolic BP, mmHg (%)||–5.1 (4)||.04|
|Diastolic BP, mmHg (%)||–6.4 (8)||.004|
|A1c*, % (%)||–0.22 (3.7)||.04|
*Among those with fasting glucose ≥ 100 mg/dL or A1c ≥ 5.7% at baseline
Participants Liked the Meal Timing
As the authors point out, studies have shown that irregular meal timing adversely affects cardiometabolic health.
"Both erratic eating patterns and eating over an extended period of time during the 24-hour day can [also] disrupt circadian rhythms," they explain.
As it turns out, time-restricted eating induces and maintains a consistent feeding and fasting cycle that supports strong circadian rhythms.
Furthermore, approximately 70% of the group also reported that they were more satisfied with the amount they slept.
"As a preventive cardiologist, I try to work with my patients and encourage them to make lifestyle changes but it is very hard to get them to make lasting and meaningful changes," co-corresponding author Pam Taub, MD, associate professor of medicine, University of California San Diego School of Medicine, noted in the statement. Taub is a consultant for Sanofi/Regeneron, Novo Nordisk, Boehringer-Ingelheim, Janssen, Pfizer, and Amgen.
"When someone has been diagnosed with metabolic syndrome, this is a critical window for intervention [as] once people become diabetic or are on multiple medicines such as insulin, it's very hard to reverse the disease process," she added.
Participants also told investigators that they found the intermittent fasting plan easier to adhere to than counting calories or trying to increase physical activity.
In fact, over one quarter of the group chose to follow the time-restricted eating strategy after completing the 12-week intervention; about one third reported they followed the strategy at least part of the time. The remainder abandoned the plan at study end.
"The high level of adherence to time-restricted eating in our study, no reported adverse effects, and low dropout rate suggest that a self-selected 10-hour window for time-restricted eating may be feasible for patients with metabolic syndrome to adhere to over a longer period of time," the investigators conclude.