Mitchel L. Zoler, PhD
August 03, 2023
Time-restricted eating (TRE) can be a practical, easy-to-follow way for some people to control their daily food intake and lose weight. It precludes a person’s need to pay close attention to how much they eat as long as they confine consumption to a limited time window. Plus, results from several recent studies show TRE can further benefit people with type 2 diabetes as well as obesity via mechanisms beyond weight loss.
The most tested and recommended eating window is 8 hours long, although periods up to roughly 10 hours may provide some benefits. Results from multiple studies document that TRE produces modest but consistent weight loss in many people of less than 5%. A recent meta-analysis of 17 randomized controlled studies involving 899 people showed an overall incremental weight loss compared with controls of 1.60 kg on a TRE regimen.
Courtney Peterson, PhD
The more limited data collected so far in people with type 2 diabetes show additional metabolic benefits from TRE including improved beta-cell responsiveness, increased insulin sensitivity, nonoxidative glucose disposal, increased time in glycemic range, and virtually no hypoglycemic events, Courtney Peterson, PhD, said at the American Diabetes Association (ADA) 83rd Scientific Sessions.
“Time-restricted eating improves glycemic control in people with prediabetes and type 2 diabetes independent of weight loss, through multiple mechanisms,” said Peterson, a researcher in the Department of Nutrition Sciences at the University of Alabama, Birmingham.
‘Eating Earlier Is Better’
Dr Lisa S. Chow
An advantage of TRE is that it is “agnostic to food preferences and quality,” said Lisa S. Chow, MD, during a separate session at the meeting. TRE “may have benefits beyond calorie restriction” that appear related to “the timing of eating and the extent of the eating window restriction. Eating earlier [in the day] is better” for markers of metabolic health regardless of how much weight a person may lose on a TRE regimen, noted Chow, an endocrinologist and professor at the University of Minnesota Medical School, Minneapolis.
But the TRE paradigm seems amenable to some flexibility on the timing for the eating window while still having benefit.
“Self-selected eating windows are usually late,” Chow observed, and because compliance with a constrained eating window matters it may be worth allowing people to choose whichever time window for eating works best for them.
“If you let people pick their eating window, they typically include dinner,” said Chow, who has run a small TRE study that showed this.
Kelsey Gabel, PhD
“To maximize the effects [of TRE] people should use the eating window that best fits their life,” agreed Kelsey Gabel, PhD, who also gave a TRE talk during the meeting. “Eating most of your [daily] calories first thing in the morning would have the best cardiometabolic benefit, but reduced adherence would mitigate the benefit,” said Gabel, a nutrition researcher at the University of Illinois, Chicago.
‘Meeting People Where They’re At’
“We can have a larger public health impact by meeting people where they’re at. People should position their eating window where it best fits so they can achieve calorie restriction without even knowing it,” Gabel advised.
She cited a 2022 report as evidence that most people prefer a later eating window. The report reviewed observational data from nearly 800,000 people who used either of two different TRE phone apps. The data showed that most people opted to start their daily eating during 11:00 AM-1:00 PM, and then stop during 6:00 PM-8:00 PM.
“TRE will not solve all of our obesity problems, but it’s a good place to start,” Gabel declared.
For people who include dinner at a typical evening time in their TRE window, a key message is that “dinner is your last food of the day. There’s no snacking later,” said Chow.
“The biggest challenge is adherence,” said Peterson. “Fewer people want to do TRE than you think. We know that calorie restriction works. We just need a way for people to do it,” and for at least some people TRE is that way. While no evidence clearly shows that 8 hours is the best eating-window duration, “we think 8 hours is a good sweet-spot for motivated people,” she said.
Sparser Data on TRE in People With T2D
Fewer studies have examined the impact of TRE on glycemic control, insulin sensitivity, and related effects in people with type 2 diabetes. According to Peterson, published reports currently include two randomized controlled studies and three single-arm studies in people with type 2 diabetes and an additional two studies in people with prediabetes.
The largest of these reports, published in 2021, randomized 120 adults in China with type 2 diabetes and overweight to TRE using a 10-hour eating window (8:00 AM-6:00 PM) or unrestricted eating for 12 weeks. By the end of the study, those on the TRE regimen had an average reduction in their hemoglobin A1c from baseline that was 0.88 percentage points greater than among the controls, and the TRE arm had also lost an average of nearly 2.15 kg more from baseline than the controls.
Peterson highlighted the importance of expanding research using TRE in people with type 2 diabetes.
Peterson and Gabel report no relevant financial relationships. Chow has received research support from Dexcom.
Mitchel L. Zoler is a reporter with Medscape and MDedge based in the Philadelphia region. @mitchelzoler.
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