As we emerge from the drowsy holidays with aspirations of being fitter and more productive, one social-media trend jumps out: How about waking up everyday at 5 a.m.?

It’s true, some of the world’s top CEOs and elite athletes swear by early rising. But sleep experts say it can set you up for failure.

“The trend of waking up at 5 a.m. is the second stupidest thing I’ve heard in a long time,” says Michael Breus , a sleep doctor in Hermosa Beach, Calif. (The first? Taping your mouth shut at night.) “If you’re a night owl who wants to get stuff done and you try waking up at 5 a.m., you’ll last a week, and you’ll become self-defeated and depressed.”

We’re a sleep-deprived nation. In a Gallup poll last year, 57% of Americans reported they would feel better if they got more sleep but said their stress prevented that. Around 20% of respondents said they got five or less hours a night. A decade ago, it was 14%, and back in 1942 it was just 3%.

Many people get less than the recommended seven to nine hours of nightly shut-eye because they want to squeeze in a workout, have some alone time or get more done. Some go-getters get up even earlier than 5 a.m.

So what time should you wake up? That depends on a few factors based on your habits, age and genetics.

Lark, bear or owl?

“Sleep is thought of as this thing that needs to be subjugated and bludgeoned into submission when really it needs to be embraced like a teddy bear,” says Russell Foster , a professor of circadian neuroscience at the University of Oxford. Studies have shown sleep deprivation can lead to heart problems, immune suppression, depression and an increased risk of dementia.

Foster isn’t a fan of the 5 a.m. wake-up, unless it comes naturally. He says your answers to these questions will indicate whether your wake-up time is too early:

• Does it take a long time to wake up?

• Do you feel you can get going immediately?

• Do you need coffee to sustain your energy?

• Do you sleep later on weekends?

Your ideal rise time is linked to your chronotype, your genetic predisposition to waking at a certain time. (If you need help understanding yours, take Breus’s quiz , which requests your name and email address.) There are morning people and night people; I’ve always joked that I’m a late-morning person. Sure enough, 55% to 65% of people are what Breus and other sleep doctors call “bears,” whose peak performance falls between the hours of 10 a.m. and 2 p.m.

Approximately 15% to 20% of the population are early birds—aka “larks”—who wake up naturally between 6 a.m. and 6:30 a.m. A small subset of larks are true 5 a.m. people. The other 15% to 20% are, you guessed it, night “owls.”

A few years ago, against my bearlike nature, I began waking at 5 a.m. I was covering a corporate beat from the West Coast and had to rise early for earnings calls and other news. The habit stuck, mostly because I enjoyed the solitude and the uninterrupted time to get work done before my three kids woke up. But I refused to get up at that hour on weekends, and as a result, it’s gotten harder to maintain that schedule.

It is possible, and often necessary, to override your chronotype and other factors in order to perform caregiving duties or get to work on time. The key is consistency.

If you get up at 5 a.m. on weekdays and sleep in until 8 a.m. on weekends, you end up with a feeling akin to jet lag, says Doug Kirsch , a North Carolina hospital medical director and past president of the American Academy of Sleep Medicine.

Tips to ensure an easy wake-up

In addition to keeping regular sleep hours, doctors say you’ll have an easier time getting out of bed if you do the following:

Get morning sunlight. Sunlight exposure in the morning signals the brain to suppress melatonin and helps you feel awake. The first light also sets an internal timer for melatonin to be produced again 14 hours later.

Consider a light gadget. If it’s too dark when you get up, especially in the winter, use a light box or an alarm clock like the Hatch Restore 3 , which slowly lights up to ease you out of slumber.

Limit caffeine and alcohol. Both can cause sleep disruption, so it’s best to cut off coffee by 2 p.m. and end alcohol consumption three hours before your bedtime, says Breus. The same goes for heavy screen use before bed.

Aim for morning workouts. Exercising increases your core body temperature, which is great for helping you wake up, but bad for getting to sleep: Your body temperature needs to drop for the sleep hormone melatonin to be produced.

Write to Julie Jargon at Julie.Jargon@wsj.com