Is a 10-Hour Eating Window Enough?

16:8 gets the headlines, so a 10-hour window can feel like the half-hearted version. Is 14 hours without food even fasting, or just not snacking after dinner?

That’s a fair question, and two trials from the same research group give a fairly direct answer. Both put adults with metabolic syndrome on a window of about 10 hours, on top of the medication they were already taking. A small pilot came first, then a randomized trial built to check it.

The answer is yes, it’s enough to move things. Just not by as much as the pilot made it look.

The short version

A 10-hour eating window improved weight, blood sugar and other markers in adults with metabolic syndrome, but the effects shrank once a proper control group was added. In the 2024 randomized trial, people on an 8- to 10-hour window lost about 1.7 kg more than people who got nutrition counseling alone, and their HbA1c fell by 0.1 percentage points more. They also ate about 350 fewer calories a day, which likely explains much of the benefit. So a 10-hour window is a real, keepable tool, and its main trick seems to be helping you eat a bit less.

The pilot: 19 people, no control group

The first study, led by Michael Wilkinson, Pam Taub and Satchidananda Panda at UC San Diego and the Salk Institute, appeared in Cell Metabolism in 2020. Nineteen adults with metabolic syndrome, most of them on a statin, blood pressure medication or both, moved all their eating into a self-chosen 10-hour window for 12 weeks. Before the study, they were eating over 14 hours a day or longer.

On average they lost 3.3 kg (about 3% of body weight), 4.5 cm off the waist, and some visceral fat. Systolic blood pressure fell about 5 mmHg, diastolic about 6.5, and LDL cholesterol about 12 mg/dL. In people who started with elevated HbA1c, it dropped too. They reported eating about 9% fewer calories.

The catch is the design. It was a single-arm pilot: everyone did the intervention and nobody served as a comparison. The authors call it an “unblinded, single-arm pilot study with relatively small sample size.” Without a control group, you can’t separate the window’s effect from simply being in a study and paying attention.

So the team ran a bigger one.

The follow-up: a randomized trial of 108 people

The TIMET trial, published in Annals of Internal Medicine in 2024, randomized adults with metabolic syndrome and raised blood sugar into two groups for three months. Both got standard nutrition counseling. One group also got a personal 8- to 10-hour eating window, at least 4 hours shorter than their usual day, and logged meal times in a phone app. 108 people completed it, with an average age of 59. At the start they were eating over about 14 hours a day.

The main result was blood sugar. Compared with counseling alone, the window improved HbA1c by 0.10 percentage points. That’s statistically real and clinically small, and the authors describe it as a modest improvement.

Weight moved more. The window group lost about 3.0 kg (3.3% of body weight) against 1.3 kg with counseling alone, a gap of about 1.7 kg. Body fat and trunk fat fell more in the window group, and blood pressure and LDL leaned the same way, though those weren’t the trial’s main test. There were no major adverse events. One person in the window group reported irritability, fatigue and trouble concentrating.

People could keep it. The average window sat at about 10 hours through the trial, and only around 12% of days had food logged more than 15 minutes outside it.

Where the benefit probably comes from

One line in the results changes how to read all of this: the window group cut its intake by about 350 calories a day, based on dietary recall. Nobody asked them to. Shutting the kitchen four hours earlier removes a lot of evening grazing.

That fits what a controlled-feeding trial found when it took the calorie difference away. When Johns Hopkins researchers gave everyone the same food, a 10-hour window added no extra weight loss over a normal eating day. Put the two together and the likely story is plain: the window works mostly because it makes eating less easier, not because the hours themselves do something special to your metabolism.

That isn’t a knock on it. A tool that trims 350 calories a day without counting is a good tool. It just won’t help if you fit the same food into fewer hours.

Is 10 hours enough, or should you go tighter?

For most people, 10 hours is a sensible place to stop rather than a stepping stone you’re obliged to push past. The trials that tested tighter windows haven’t shown a clear extra payoff. In one, a 4-hour window did no better than a 6-hour one, and stricter schedules are harder to keep.

A 10-hour day also leaves room for a normal life: breakfast at 9, dinner by 7, and you’re done. In the TIMET trial the average window ran from a little after 9 in the morning to around 7 at night. That’s a schedule you can keep through work dinners and weekends.

What these studies don’t settle

Both trials were in adults with metabolic syndrome, many on medication. If you’re healthy and lean, the gains could be smaller, and these studies can’t tell you. Three months is short, so neither trial says what happens over years. The randomized trial measured diet by recall, which tends to undercount, and it used its own app and coaching, so the real-world version may be looser.

The biggest open question is the one above: how much of the effect is timing and how much is eating less. The trials can’t separate those, and the feeding study suggests it’s mostly the second.

What to do with this

• Start at 10 hours if 16:8 feels like a fight. It’s a real fast of 14 hours, and the evidence for it is about as good as the evidence for tighter windows. Picking a window you’ll keep beats picking the strictest one.
• Close the window at the same time each night. In both trials the window was consistent day to day. The late-evening cut is where most of the 350 calories probably came from.
• Watch what goes into the 10 hours. If the calorie gap is the mechanism, a window filled with the same food as before won’t do much.
• If you take medication for blood sugar or blood pressure, talk to your doctor first. Both trials ran alongside existing treatment under medical supervision, and fasting can change how those drugs act.

Atomic Fast’s timer is free and fits a 14:10 schedule. You start each fast yourself (now, backdated to your last logged meal, or scheduled up to 24 hours ahead), and the timer shows how long you’ve gone and which metabolic phase you’re in by the hours elapsed. On a 14-hour fast, that means it ends during the phase the app calls Fat Burning, by the clock rather than any reading of your body. If you also log meals, by photo, a quick typed description or a barcode, today’s fasts and meals sit together on one daily timeline, which makes it easy to see whether the window is doing its real job: trimming what you eat.

Frequently asked questions

Does a 10-hour eating window count as intermittent fasting? Yes. It’s a daily 14-hour fast, often written 14:10. The randomized trial covered here used 8- to 10-hour windows and called it time-restricted eating, one form of intermittent fasting.

How much weight did people lose on a 10-hour window? In the 2024 randomized trial, about 3.0 kg over three months, versus 1.3 kg with nutrition counseling alone. The 2020 pilot saw about 3.3 kg in 12 weeks, but it had no control group.

Does a 10-hour window lower blood sugar? A little. In the randomized trial HbA1c fell 0.10 percentage points more than with counseling alone, in adults with metabolic syndrome and raised blood sugar.

Is 16:8 better than 14:10? No trial here compared them head to head. Research on tighter windows hasn’t shown a clear extra benefit, so the better one is usually whichever you’ll stick with.

Can I do a 10-hour window if I take statins or blood pressure drugs? Most people in both trials did, under medical care. Check with your doctor first, especially for glucose-lowering drugs, since eating less can change your dose needs.

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Try a 14:10 schedule with Atomic Fast, free on the App Store and Google Play.

This article is for general education and isn’t medical advice. If you’re pregnant, managing a health condition, taking medication, have a history of disordered eating, or are considering fasts longer than 24 hours, talk to a healthcare professional first.