Time-Restricted Eating, Demystified: Benefits, Risks, & Finding Your Schedule

Time-restricted eating is a form of intermittent fasting that involves limiting your food intake to a specific window of time each day.

In most cases, people will limit their food intake to a 6-12 hour slot and fast during the remaining hours outside of this time period. Though some people limit their intake during fasting periods to water only, others may choose to opt for calorie-free beverages, like black coffee or tea, or eat a small number of calories.

In recent years, TRE has soared in popularity thanks to the unique flexibility that it offers. Contrary to other diet plans that focus on meticulously measuring grams of carbs, fat, or protein, TRE doesn’t require you to log your food intake and enables you to eat whatever you choose within a specific time period each day.

Plus, TRE doesn't make you majorly restrict calories like other forms of fasting such as alternate-day fasting, one meal a day (OMAD), and 5:2 fasting.

Summary

Time-restricted eating (TRE) involves restricting the number of hours a day that you eat food—usually to a 6-12 hour window. There aren't typically restrictions on what you can eat during your feeding window.

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1.

It can enhance longevity by promoting cellular repair and autophagy.

According to Humaira Jamshed, Ph.D., a researcher and assistant professor at the Dhanani School of Science and Engineering, TRE has been shown to promote cellular repair1 and autophagy, a process in which the body breaks down damaged cells and replaces them with healthy new cells.

“Research suggests that autophagy2 may have a protective effect against aging, cancer, and other diseases,” says Jamshed.

In one study conducted by Jamshed and her colleagues, participants followed an early time-restricted eating plan for four days, which involved limiting their food intake to the hours of 8 a.m. to 2 p.m. each day. By the end of the study, researchers observed increased markers of autophagy1, suggesting that TRE could potentially have anti-aging effects.

Impressively enough, one 2022 animal study also found that restricting food intake to a 2-hour window of time each day increased the lifespan3 of mice by a whopping 35 percent. Researchers in this study concluded that TRE could reduce inflammation and other age-related changes, resulting in enhanced longevity.

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2.

It can promote weight loss via calorie restriction.

“TRE may be promising for people who have struggled with weight loss or calorie counting in the past,” explains Kelsey Gabel, R.D., Ph.D., an assistant professor and intermittent fasting researcher at the University of Illinois at Chicago.

“From the current data, it appears that people naturally restrict calories4 by about 20% when eating in a shorter window every day. This seems to result in somewhere between a 2-4% weight loss in 2-3 months without counting calories,” says Gabel.

While it may sound too good to be true, this was actually confirmed in a 2018 study4 conducted by Gabel and other researchers. The study found that, on average, people who limited their food intake to an 8-hour period each day consumed 341 calories less per day and lost 2.6% of their body weight over a 12-week period.

Jamshed notes that TRE may also help regulate levels of ghrelin and leptin, two hormones involved in regulating hunger and satiety. Interestingly, one study found that early time-restricted eating increased feelings of fullness, decreased the desire to eat, and reduced levels of ghrelin (the “hunger hormone”), all of which could potentially boost weight loss5.

3.

It might help with blood sugar regulation.

In addition to supporting weight loss, TRE may promote other aspects of metabolic health as well. “TRE is currently being explored for blood sugar regulation in individuals with pre-diabetes and even type 2 diabetes,” says Gabel.

Jamshed adds that it may help reduce insulin resistance6 and increase insulin sensitivity, which can improve your body’s ability to use insulin to regulate blood sugar levels effectively.

A recent review by Gabel and colleagues theorized that the benefits of TRE could stem from its ability to6 stimulate autophagy, reduce oxidative stress, and increase the responsiveness of insulin-producing cells in the pancreas.

Research-backed tip:

Pairing TRE with exercise might even amplify the metabolic benefits. A 2022 study found that limiting food intake to less than 10 hours per day and participating in three sessions of high-intensity interval training (HIIT) per week improved hemoglobin A1c, a marker of long-term blood sugar control, and decreased body fat more significantly than either TRE or HIIT alone.

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Early TRE usually restricts food intake to a period earlier in the day and involves fasting in the early afternoon.

Sticking to an early eating schedule may help you get the most bang for your buck, according to Jamshed.

“This method helps correct circadian misalignments7, and eating in sync with the external cues of daylight helps improve health,” says Jamshed, who also notes that it may be the most effective option for improving metabolic health, weight loss, mood, and sleep.

This is also reflected in multiple studies, which have linked an early time-restricted eating schedule to improved insulin sensitivity8, decreased oxidative stress8, increased weight loss9, and reduced blood pressure levels9.

However, this plan may be challenging to stick to, especially as it involves forgoing family dinners, happy hours, and late-night snacks. It might also not be a good fit if you sleep in or prefer eating your morning meal a bit later in the day.

Here’s what this meal plan may look like:

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Midday TRE involves limiting your food intake to the middle of the day, often by skipping breakfast and eating an early lunch.

“This approach may be more practical for those with work schedules that require a midday meal, and may still offer some of the potential benefits of early TRE,” says Jamshed.

However, it may not align with your natural circadian rhythms as well as early TRE, she says, which could diminish some of the possible benefits. In fact, one study comparing the two methods found that early TRE was more effective at improving insulin sensitivity10 than midday TRE.

Early TRE was also associated with reductions in body weight, fasting blood sugar levels, and inflammation, whereas midday TRE was not.

Below is a sample meal plan for this TRE schedule:

Late TRE generally requires you to skip breakfast and eat a late lunch.

Jamshed states that this could be a good option for people who prefer to socialize or eat dinner later in the day, noting that it may still offer some of the benefits of TRE.

In fact, a recent trial11 comparing early and late TRE found that both resulted in similar amounts of weight loss compared to a control group. However, early TRE still had an edge over late eating, especially in terms of its effects on blood sugar, blood pressure, fasting insulin, and insulin resistance.

According to Jamshed, late TRE may not be ideal for blood sugar control and fat burning, as our body’s sensitivity to insulin tends to decline12 in the evening. “Additionally, eating close to bedtime may disrupt sleep quality for some individuals,” she says.

If you’re interested in trying late TRE, here’s a sample schedule:

“Placing the eating window earlier in the morning (finishing the 8-hour window by 2-3 p.m.) may have more benefits for glucose control,” says Gabel. Jamshed agrees, noting that early TRE may be the most effective option when it comes to metabolic health, weight loss, and mood.

However, both also acknowledge that this eating pattern may be harder for some people to follow, as many people prefer socializing in the evenings and enjoying dinner with family or friends.

Jamshed emphasizes that there’s no single “best” type of TRE for everyone, as the most appropriate option can vary depending on many individual factors. “It’s important to choose a TRE method that is sustainable and enjoyable, and to speak with a healthcare professional before starting any new dietary or lifestyle regimen,” she says.

Ultimately, it may be best to tailor your eating pattern to your individual schedule and experiment with the precise timing to find what works for you.

And as far as how long to fast, if you’re new to time-restricted eating, consider checking out 18:6 and 16:8 fasting plans, both of which involve abstaining from food for 18 or 16 hours each day, respectively.

While there’s no one-size-fits-all plan when it comes to time-restricted eating, these are two of the most popular and beginner-friendly variations.

Summary

Early TRE (stopping eating in the late afternoon) is the most effective time window for weight loss and metabolic health, but it can be difficult to stick to. Ultimately, the best TRE window for you will be the one that fits into your lifestyle.

Though TRE may offer several possible health benefits, it’s not a good fit for everyone. Gabel states that intermittent fasting in general is not recommended for children, adolescents, people with a history of eating disorders, and those who are underweight.

Additionally, she notes that there is limited research on the safety of fasting for other groups, including people who are pregnant or lactating and individuals over the age of 70.

Jamshed points out that there are several possible time-restricted eating side effects to keep in mind, including:

Time-restricted eating is a flexible eating pattern that may offer benefits in the long run, including increased weight loss and improved metabolic health. Additionally, there are several variations available, making it easy to incorporate TRE into your schedule.

However, TRE isn’t a good fit for everyone and may be associated with negative side effects, some of which can be serious. For this reason, it’s best to talk to your doctor to see if TRE is worth a try and how it may impact your health. If you do decide to try TRE, these tips can make it easier to follow.