Bringing You New Sleep Insights

Arivale Team,
Arivale Team

Many Arivale members want to prioritize adequate rest, but struggle. Whether you’re having trouble falling and staying asleep, we get it. Our research team doubled down on the numbers to analyze Arivale’s sleep data to better inform your wellness plan.

Our research scientists examined the BMI and Fitbit sleep data of 471 Arivale members over the course of a year. As it turned out, the results of this analysis were so interesting the study was published in The International Journal of Obesity. In this blog post, we’ll give you a brief summary of the results.

Arivale discovered awesome sleep isn’t just about quantity.

There’s nothing like a night of insomnia to reinforce the importance of sleep. Both for next-day mental clarity and your long-term wellness, sleep is critical to good health.  Besides affecting your level of energy, the quality of your shut-eye can influence risks for heart disease, diabetes, immune disorders, mental health challenges, obesity, and more. (1,2)

Despite this, we tend to burn the midnight oil to squeeze in other “more important” things. Statistics on the US population show that the prevalence of insufficient sleep has increased by almost two-fold over the last three decades (3). Furthermore, a body of research demonstrates that shorter habitual sleep duration is associated with obesity and increased body mass index (BMI) (4).

Just like nutrition and activity, we need to prioritize sleep for optimal wellness.

An Unexpected Benefit of One Hour of Sleep

Our research team validated previous studies showing that more sleep did correlate with lower BMI. More specifically, after adjustment for other factors, every additional hour of sleep was associated with a BMI that was lower by 1.13, on average across the Arivale population.  This change in BMI roughly translates to 8 pounds for an average-height American man (5’10”), and 6.5-pounds for an average-height American woman (5’4”).

Don’t pull out your pillow just yet. More than nine hours per night has been associated with poor health outcomes and can be detrimental as well. Because of this, the current medical literature advises seven to nine hours of sleep per night. (5)

The Kicker to Sleep is Consistency

Sleep consistency is measured by “variation.” Think of it like this: On any given night, John generally sleeps between five and nine hours, but over two weeks he averages seven hours per night. John does sleep exactly seven hours (the average) a few nights, but most nights his amount of sleep differs: six hours, eight hours, nine, etc. We call this behavior—the lack of consistency in your sleep time—your “variation.”

Our research team found lower variation (more consistency) was associated with lower BMI independently of sleep duration and other factors.  Interestingly, the effect on body weight was even bigger for sleep variation compared to sleep duration – something that has not previously been known.

This is the first time, to our knowledge, that sleep consistency as well as sleep duration had been associated with body weight.

Correlation, Not Causation

Our research into the relationship between body mass and sleep led to exciting findings. But please note: These are associations, not causations. If you change your sleep regimen to achieve a perfect eight hours every night, your weight likely won’t decrease as a direct result of that single change alone.

But, if you do endeavor to improve your sleep duration and consistency, you may just find as a result, you have more energy, mental clarity, and make better food choices (to name a few benefits). And the sum of these changes and results may just prove to be a turning point in your wellness.

Don’t Miss What’s New on Your Dashboard

If you’re an Arivale member, you can see your sleep duration and consistency (along with a comparison to other Arivale members) on a new dashboard page totally dedicated to sleep. Additionally, you’ll see three new genetics insights – Are you a morning or night person? Do you tend to sleep more or less? Does caffeine keep you awake at night? – as well as your sleep-related action items, things to consider when you need more sleep, and the downsides of poor sleep.

We look forward to hearing what you think about the new sleep insights page. And remember, wear your Fitbit to sleep at least four nights a week (including weekends!) to get the most of out of your data.


  1. NIH Why Sleep Is Important. National Heart, Lung, and Blood Institute. 2018.
  2. Sleep Duration and Quality: Impact on Lifestyle Behaviors and Cardiometabolic Health: A Scientific Statement From the American Heart Association doi: 10.1161/CIR.0000000000000444 Circulation. 2016;134:e367-e386. Originally published September 19, 2016.
  3. Trends in Self-Reported Sleep Duration among US Adults from 1985 to 2012.Ford ES, Cunningham TJ, Croft JB. Sleep. 2015;38(5):829-832. doi:10.5665/sleep.4684.
  4. The effects of partial sleep deprivation on energy balance: a systematic review and meta-analysis.Al Khatib HK, Harding SV, Darzi J, Pot GK. Eur J Clin Nutr. 2017 May;71(5):614-624. doi: 10.1038/ejcn.2016.201. Epub 2016 Nov 2. PMID: 27804960
  5. National Sleep Foundation’s sleep time duration recommendations: methodology and results Hirshkowitz, Max et al. Sleep Health: Journal of the National Sleep Foundation, Volume 1, Issue 1 , 40 – 43.