There’s plenty of advice online about how to stay energized. You can take an adult multivitamin in the morning, do a light workout or eat nutritious foods to power up. Getting enough rest is on the list, too, but the quantity (and quality) you need isn’t always clear. Plus, one of the most important facts is usually missing: The other tips are less effective if you aren’t sleeping well.

“Everything you do, you do better with a good night’s sleep,” Dr. Michael Breus says. “Skimping on the resource that can absolutely, positively make your day better in any way you can imagine appears to be a bit foolish.”

Breus, a sleep doctor, sees plenty of exhausted patients—people who seemingly do everything right but still lack energy. In response, he conducted years of research to find the cause and help people regain control. In this episode of Brilliant Thoughts, he discusses the basics of rest with SUCCESS People Editor Tristan Ahumada.

How many hours of sleep do you really need?

We’ve all heard the warning that adults need eight hours of sleep, or else. But that’s a blanket statement that doesn’t consider a person’s age, gender or medical condition.

Here’s the actual math behind sleep, according to Breus: If you consider the fact that the average sleep cycle is 90 minutes, and people average five cycles per night, that gives you 450 minutes of rest. Dividing 450 by 60 does not equal the eight hours of sleep most people are chasing; it’s actually 7.5.

“Stop thinking, ‘Oh my gosh, I’ve got to kill myself to get eight hours of sleep,” Breus says. “That’s not necessarily true.”

Sleep quantity vs. sleep quality

Getting 7.5 hours of sleep is a good starting point, but the quality of your rest is just as important. Otherwise, you could wake up feeling tired after a long night of sleep.

“People are always like, ‘How many hours do I need?’ That’s a quantity measure,” Breus says. “That measure will change based on your quality. Higher quality [equals] less quantity. That’s what we’re shooting for, for entrepreneurs.”

Breus wanted to test this theory, so he decided to go to sleep at midnight consistently. In the beginning, he woke up naturally at 7:15 a.m. But as the experiment went on, he started rising earlier: 7 a.m., 6:30 a.m. and eventually 6:15 a.m. He didn’t use an alarm clock to wake up, and he never experienced insomnia. So even as a sleep doctor—someone who might champion the eight-hour rule—Breus got what he needed in six hours. He chalks it up to sleep efficiency, which can shrink the number of hours you spend in bed.

The almighty chronotype: why no sleep routine is complete without it

Can you get six hours of sleep and still have a productive, energized day? As it turns out, the answer is hiding in your genes; some people wake up early or sleep late because of their natural coding.

“It’s not like you can choose [and say], ‘I want to join the 5 a.m. club and be an early bird,’” Breus says. “It doesn’t really work that way.”

Your chronotype is what determines your best sleep schedule. Chronotypes are behavioral outcomes based on your genetics, and they explain your propensity for sleeping at certain times.

Here are the four chronotypes, reimagined by Breus to give more context:

• Lions: People in this chronotype rise before the sun. They’re perpetual doers with long to-do lists and perhaps a startup or two. They represent 15% of the population.
• Wolves: These are what most people consider night owls—artists, actors, musicians and other creative types. Wolves rarely sleep before midnight and represent 15-20% of the population.
• Bears: Not quite wolves and not quite lions. This chronotype is right in the middle and represents a whopping 50-55% of people. Bears follow the standard schedule: waking up at 7:30 a.m. and going to bed by 10:30 p.m.
• Dolphins: This chronotype is never quite asleep. Dolphins could have a genetic form of insomnia or simply have trouble relaxing at night.

If you’re unsure of your chronotype, take Breus’ Chronoquiz to see where you fit in.

Mixing chronotype with body type

The interesting thing about chronotypes is how much they relate to body types, Breus says. Knowing whether you’re an ectomorph (long and lean), mesomorph (V-shaped and muscular), or endomorph (weight in the hips/belly) can help you make better lifestyle choices.

“It turns out that the old idea of endomorph, mesomorph, ectomorph is really based on metabolism,” he says. “The long and lean appear to have a fast metabolism, the mesomorphs in the middle appear to have a medium metabolism, and the endomorphs appear to have a slower metabolism.”

So if you’re an endomorph, you’re probably not a lion (early riser), and you probably don’t need to eat breakfast as soon as you wake up, he says. You can fast until noon or later because you’re not using all your energy in the morning (assuming you wake up later). On the flip side, lions should eat breakfast sooner because they’re active earlier. Breus offers more information about chronotypes and body types in his new book, Energize!: Go from Dragging Ass to Kicking It in 30 Days, co-authored with SoulCycle founder Stacey Griffith.

How to boost your energy overall

Even if you don’t know your body type or chronotype, there are ways to increase your energy over time.

Here’s what Breus recommends:

• Wake up every day at the same time, even on weekends. A consistent sleep routine will help you feel your best.
• Aim for seven or so hours of sleep, but know that you might need less depending on your chronotype and how efficiently you rest.
• Take naps regularly to boost your energy.
• If you have a sleep condition (narcolepsy, sleep apnea, etc.), speak to your doctor to reclaim some much-needed rest.

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Written by Lydia Sweatt