If you’re wondering what the optimal times are to engage in certain activities, listen to your body’s circadian rhythms. Circadian rhythms are physiological, mental and behavioral changes governed by the body within a 24-hour clock, according to the National Institute of General Medical Sciences. They are affected by environmental cues, such as sunlight, darkness and temperature.
Circadian rhythms influence sleep/wake cycles, hormone release, body temperature and other important bodily functions, and these rhythms change as we get older. In the mornings with exposure to light, the brain sends signals to raise body temperature and produce hormones like cortisol, reports the National Sleep Foundation. Cortisol is produced in response to stress as well as according to natural circadian rhythm cycles. It helps give us energy in the morning, and levels decrease throughout the day. The brain also responds to light by delaying the release of other hormones like melatonin, which is associated with sleep and produced when we’re exposed to darkness. Melatonin levels rise in the evening and stay elevated throughout the night, promoting sleep. All this means that, based on age, there is a best time to be doing everything in our lives, like going to sleep and waking up, exercising, and even having a cocktail.
As we get older, the melatonin in our bodies starts decreasing, so we wake up earlier and earlier. The change begins in our thirties. A study from Paul Kelley and Oxford University states that the ideal wakeup time when we’re in our twenties is 9:30 a.m.; in our thirties, 8 a.m.; in our forties, 7:30 a.m.; in our fifties, 7 a.m.; and in our sixties, 6:30 a.m. This means, of course, we need to adjust our bedtime to match our wakeup time to get the rest we need.
The National Sleep Foundation recommends adults get the following amount of sleep:
- Adults — 7 to 9 hours
- Older Adults 65+ — 7 to 8 hours
Our abilities to focus and perform are also affected by circadian rhythms. The best time to start work is 2.5 to 3 hours after you wake up. That’s when we’re past the sleep inertia or grogginess stage, and when we’re at our most alert. For someone in their twenties, that’s around noon. Unfortunately, American society is radically out of whack with work and school start times, and most of us aren’t self-employed and can’t begin work at 11 a.m. or 12 p.m. We are a culture of do more and sleep less.
The optimal time to work out is around four hours before bedtime – that’s when we’re at our peak strength and lung function. In your thirties, that’s around 7 p.m.; in your forties, 6 p.m.; and in your fifties, around 5 p.m.
Since people in their twenties often enjoy a bedtime as late as 1 a.m., a meal at around 9:30 serves as an energy boost. An 8 p.m. meal is ideal for people in their thirties and forties. People in their fifties should eat dinner around 7 p.m. and in their sixties, around 6:30, to leave optimal time to digest (and avoid heartburn).
As we get older, our liver function decreases. If you’re going to enjoy an alcoholic beverage, you want to have it when the liver is functioning at its peak. For most ages, it’s best to give your body at least four hours to process alcohol before bedtime.
Cicadian rhythms are really useful regulators of bodily functions. As the saying goes, listen to your body and you’ll enjoy the most efficient, healthy outcomes.
See my interview on this topic with Elizabeth Prann, Clayton Morris and Tucker Carlson on Fox & Friends.