How long before bed should you stop eating?

Give yourself about 2 to 3 hours between your last bite and going to bed, so if you're in bed at 11, you want to be done eating somewhere between 8 and 9.

That might already be how your evenings go. You get home from work, get dinner made and get everyone fed, and it's 7 or 8 before you've finished eating yourself. If you're in bed around 11, that's fine, and you don't need to move dinner any earlier. Ideally, you don't want to go to bed too full or too hungry, so if an early dinner leaves you hungry by bedtime, eat a little later.

If you get heartburn, the gap matters, because going to bed less than 3 hours after eating is linked with more heartburn and reflux ¹. For everyone else, it's less clear that a late dinner hurts your sleep. The studies on it point both ways ²³.

When dinner can't happen until 9 or later

Some nights you don't sit down until 9 or 9:30, because work ran late or the kids had practice. On those nights I'd still eat rather than skip dinner. Make the late meal the smallest one of the day, something like a sandwich or a bowl of soup. It's easier to keep it small if you've had a proper lunch and something filling around 5 or 6, so you're not starving when you walk in the door.

Once you've eaten, stay sitting up for a while instead of stretching out on the couch, since lying down within 3 hours of eating is linked with more heartburn too ¹. Do the same after a big dinner out that runs late, so you're not walking in the door and going straight to bed.

If late dinners give you heartburn

The American College of Gastroenterology gives people with reflux the same 2 to 3 hours before bed ¹. They admit the evidence behind it is thin ¹, so treat it as something to try and see how you feel.

Keep the late meal plain, too. Spicy, fatty and acidic foods, like tomato sauce, can set off heartburn, and so can coffee, chocolate and soda ¹. You probably already know which ones get you. Have those at lunch instead of at a late dinner.

If heartburn keeps waking you at night, raise the head of your bed ¹. It also helps to sleep on your left side, because lying on your right side brings on more reflux at night ¹.

How meal times affect your body clock

You probably think of your body clock as something in your brain, and that's where the main one is. But most of your organs keep their own daily clock too ⁵. The one in your brain keeps them all in step ⁵. Light sets the clock in your brain more than anything else ⁵. For the clocks in the rest of your body, when you eat is a strong signal too ⁵.

When 10 healthy young men in a lab had all their meals moved 5 hours later for 6 days, parts of their body fell out of step with their brain ³. The daily rise and fall of their blood sugar shifted more than 5 hours with the meals ³. Their melatonin, which tracks the clock in the brain, stayed put, and so did the time of day they felt sleepy ³. Day to day, keep your meal times roughly the same where you can.

Should you try an eating window?

An eating window, also called time-restricted eating, means fitting all your food into a set number of hours each day. Usually that cuts the normal 12 to 14 hours down to under 10 ⁵. Much of the research has been in mice, and the studies in people have mostly been small and short ⁵.

In one of the first studies, overweight adults who shortened their eating window also ate about a fifth less without being asked to, going by their own records ⁵. That makes it hard to tell how much the timing itself did ⁵. There isn't enough evidence yet to recommend fasting diets in general ⁶. I'd put the effort into stopping 2 to 3 hours before bed.