- An 8-hour eating window was linked to greater weight loss than a 12-hour window or no time restriction, but not significantly more than a 10-hour window.
- Time-restricted eating (TRE) is a form of intermittent fasting that limits eating to a set number of hours each day without necessarily restricting calories.
- Shorter eating windows were linked to modest weight loss, but researchers found limited effects on blood pressure, blood sugar, and cholesterol.
Limiting your eating to an 8-hour window may result in more weight loss than a 12-hour window, according to a new study published in the journal
The eating window is followed by fasting for the remaining hours. Common approaches include 16:8, which involves 16 hours of fasting and 8 hours of eating, and early TRE, which involves eating earlier in the day.
The researchers used data from 124 adults across five TRE trials lasting between 3 and 6 months. At baseline, participants had an average eating window of about 15 hours and at least one component of metabolic syndrome.
Their food and beverage intake was tracked using an app.
Participants were assigned either to a TRE group or to the control group. The control group participants maintained their habitual intake, received nutritional counseling, or were given guidance on healthy eating.
Those in the TRE group limited their eating windows to 8, 10, or 12 hours, with no restrictions on dietary quality or energy intake.
After 3–6 months, the researchers found that participants assigned to an 8-hour eating window lost about 3.7 pounds (1.7 kg) more than those assigned to a 12-hour window and about 5 pounds (2.3 kg) more than those in the control group.
However, there was no statistically significant difference in weight loss between the 8-hour and the 10-hour windows. The 8-hour window also showed no significant impact on blood pressure, glucose, or cholesterol.
“The findings are interesting and add to the evidence that shortening the daily eating window may help with weight loss, but I would be cautious about concluding that eight hours is the optimal window,” Dalia Perelman, MS, RDN, CDCES, research dietitian at Stanford Medicine, who wasn’t involved in the study, told Healthline.
“One finding I find particularly interesting is that people who shortened their eating window more relative to their usual pattern tended to lose more weight. This suggests that the benefit may not be about everyone following exactly the same eight-hour window, but rather about meaningfully shortening one’s habitual eating period,” she added.
The researchers also found that the 10-hour eating window significantly reduced systolic blood pressure compared with the 12-hour window. There were no significant differences between the eating windows for glucose or lipids.
However, a 2020 study found that a 10-hour eating window reduced weight, blood pressure, and cholesterol, among adults with metabolic syndrome who were already taking medication.
“[These] effects are generally modest, and TRE should be viewed as one potential component of an overall lifestyle approach rather than a treatment on its own,” said Perelman.
“I think TRE is best viewed as one possible tool rather than a magic formula. When we eat appears to matter, but what and how much we eat still matter as well,” she added.
“A nutritious diet, limiting highly processed foods, avoiding eating late at night, and finding an eating pattern that is enjoyable and sustainable are probably more important than rigidly adhering to a specific number of hours.”
As with any eating plan, time-restricted eating should be realistic and sustainable for your lifestyle.
Perelman noted that health is about more than what and when you eat. She said that sharing meals with family and friends, social connection, and enjoyment of food are important too.
A rigid eating schedule that interferes with those things may not be beneficial overall.
“Rather than focusing on achieving a precise eight-hour window, I would prioritize a balanced, nutrient-rich diet low in highly processed foods and, when possible, finish eating earlier in the evening,” Perelman said.
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