Eat all meals in a 10-hour window

Why late snacks add up

When researchers asked adults to photograph everything they ate with a phone app, more than half were eating across 15 hours or more a day. A large share of their food came late in the day, often as small snacks people barely noticed. Those extra bites add calories without ever feeling like a meal.

Timing may matter a little too. In studies, the body tends to handle sugar less smoothly in the evening than in the morning. So the same snack can leave blood sugar higher for longer when you eat it late at night.

What a set window changes

Your body runs on daily rhythms, often called your body clock. The clock in your brain follows light, while clocks in your liver and gut also respond to when you eat. Eating at roughly the same times each day helps keep these rhythms in step.

A set window also gives you a clear rule about when eating is done for the day. That rule often trims late snacks without any calorie counting. It also creates a long overnight break from food, roughly the hours you sleep plus a little extra.

What the research found

In a 2020 study, 19 adults with metabolic syndrome ate within a 10-hour window for 12 weeks. Metabolic syndrome is a cluster of risks such as high blood pressure, high blood sugar and extra belly fat. On average, they lost about 3% of their body weight and had lower blood pressure and LDL cholesterol. In an earlier study, eight overweight adults narrowed their eating to 10 to 11 hours a day for 16 weeks, lost weight, and said they slept better.

These studies were small and had no comparison group, so they show links rather than proof. A larger trial of 116 adults tested an eight-hour window for 12 weeks and found no more weight loss than eating as usual. That also answers a common question: a narrower window has not shown extra benefit, so there is no need to squeeze tighter than 10 hours. Reviews conclude that much of the effect probably comes from eating a little less overall, so expect a modest change over weeks.

Making it stick

Build your window around the evening, because that is when eating most often drifts late. Note when you usually finish dinner, then count back to find when your first meal or milky coffee can begin. If you finish dinner at 7:30 p.m., a 10-hour window opens at 9:30 a.m. If that feels tight, start with 12 hours for a couple of weeks and narrow it later.

Outside your window, water, plain tea and black coffee are fine, and a freshly brushed set of teeth makes a surprisingly firm bouncer. Life will bring late dinners and birthday cake, so enjoy them and start the next day's window a little later. On an ordinary evening, dinner closes the kitchen and you head for the couch empty-handed, and soon you are someone who simply doesn't snack after dinner. If you are pregnant, take medication for diabetes, or have a history of eating disorders, talk with your doctor before changing when you eat. What time does your dinner usually end on a weeknight?

References

• Gill, S., & Panda, S. (2015). A smartphone app reveals erratic diurnal eating patterns in humans that can be modulated for health benefits. Cell Metabolism, 22(5), 789–798. doi.org/10.1016/j.cmet.2015.09.005
• Wilkinson, M. J., et al. (2020). Ten-hour time-restricted eating reduces weight, blood pressure, and atherogenic lipids in patients with metabolic syndrome. Cell Metabolism, 31(1), 92–104. doi.org/10.1016/j.cmet.2019.11.004
• Lowe, D. A., et al. (2020). Effects of time-restricted eating on weight loss and other metabolic parameters in women and men with overweight and obesity: The TREAT randomized clinical trial. JAMA Internal Medicine, 180(11), 1491–1499. doi.org/10.1001/jamainternmed.2020.4153
• Manoogian, E. N. C., et al. (2022). Time-restricted eating for the prevention and management of metabolic diseases. Endocrine Reviews, 43(2), 405–436. doi.org/10.1210/endrev/bnab027