Counting Calories? Eating Late Affects Your Weight and Your Circadian Rhythm

Do you share you home with a cat or dog? Then you’re also likely to share your bed with them around 4 a.m. when they nuzzle some uncovered body part to wake you up and announce in no uncertain terms, “Feed me.”

What’s happening here? Circadian rhythm, a biological imperative governed by a bunch of nerve cells called the suprachiasmatic nucleus (SCN) that functions as a kind of body clock, activated by light and synchronized to the 24-hour solar day .

At its most basic, your circadian rhythm primes you to be alert when it’s light and drowsy when it’s dark. And not just you. Animals from lions to lizards also have this although sometimes with modifications. Felines for example are more active at night. In ways not quite understood, it also moves some plants to move their leaves at the same time every day looking for light even in total darkness.

It should come as no surprise to hear that it’s also an important part of your dietary regimen. Frank Scheer, a professor of medicine in the Division of Sleep Medicine at Harvard School of Medicine MS and a senior neuroscientist in the Division of Sleep and Circadian Disorders at Brigham and Women’s Hospital explains that the clock in your gut is primed to receive food during the day. Nighttime meals and snacks turn out to trigger a slew of metabolic changes.

If you dine at nine, you burn 10% less calories

Like what? Two years ago, John Hopkins researchers published a small study in the Journal of Clinical endocrinology and Metabolism showing that people who ate dinner at 9 PM burned as much as 10 percent fewer fat calories overnight than those who ate the exact same meal three hours earlier. A similar study in the journal Nutrients reported that eating later in the evening may impact your weight because your body’s ability to burn calories seems lower at night than throughout the rest of the day.

What’s working here are your hormones, specifically ghrelin which stimulates appetite and leptin which tells your brain you’re full. While every body is different, eating late in the day appears to lower leptin levels, so the message you get is “More food, please.” More food means more calories to burn which is unlikely to happen while you’re sleeping. That’s is exactly what a Scheer’s team reported early this month in Cell Metabolism, confirming once and for all the value of eating when the sun is up.

In other words, the solution is to time your meals to keep your hormonal metabolism humming steadily by ignoring the three-meals-a-day mantra and making that four meals, at three- or four-hour intervals during the day while you’re awake and active.

Not the easiest thing to do when you’re working or otherwise running around in the world. But master the task and your scale will thank you.

And so will your waistline.