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Experts say poor sleep can be caused by irregular eating habits and stress. They note that bad sleep patterns can also cause those health issues. Getty Images
  • Researchers say poor sleeping patterns can lead to weight gain and an increase in body mass index.
  • They say the extra weight can lead to health issues such as high blood pressure, type 2 diabetes, and coronary artery disease.
  • Researchers say caffeine and alcohol intake, as well as impulsive behaviors, can result in poor sleep.
  • They recommend people set a regular bedtime and wake-up time, and make sure their bedroom is primarily for sleep.

Not getting enough sleep or having inconsistent sleeping patterns is associated with a higher body mass index (BMI).

Researchers in a study published in the journal JAMA Internal Medicine used Fitbit wearable technology to collect sleep data from more than 120,000 people over a 2-year period.

“We examined the hypothesis that shorter sleep duration (hours slept at night) and greater day-to-day variability of sleep duration (standard deviation of hours slept at night) are associated with increased body mass index (BMI),” the study authors wrote.

They found that those in the study with a BMI over 30 (what’s considered the obesity range) had slightly shorter sleep durations and more variability in their sleep.

“These findings provide further support to the notion that sleep patterns are associated with weight management and overall health. The findings also support the potential value of including both sleep duration and individual sleep patterns when studying sleep-related health outcomes,” the researchers wrote.

This isn’t the first study to suggest a link between poor sleep and weight gain, but the authors argue the use of wearable technology like Fitbits gives researchers the opportunity to accurately track participants discreetly, without relying on memory of the participants’ for data.

“Most population-level sleep data are limited by recall bias, cross-sectional nature, and lack of detail regarding sleep habits over months to years. The recent increased uptake of wearable sensors (also known as activity trackers) has made such longitudinal data increasingly obtainable with digital devices that offer unobtrusive monitoring of multiple health parameters, including sleep,” the researchers wrote.

Experts say the findings of the study aren’t surprising.

“That has been known previously that short or long sleepers have higher BMI,” Dr. Kimberly A. Hardin, the director of the Sleep Medicine Fellowship Program at the University of California Davis, told Healthline.

“Poor sleep is causing the increased BMI. Poor sleep results in qualitative and quantitative sleep deprivation. The [consequences] are daytime sleepiness and poor productivity,” she said.

“Lack of energy and sleepiness or fatigue are often combated by caffeine and sugar, leading to weight gain and less exercise,” Hardin added.

Among the 120,522 participants involved in the study, the mean sleep duration was 6 hours and 47 minutes a night. Experts say this falls short of the optimal amount of sleep that’s recommended.

“In general, you want to get at least 7.5 hours of sleep on a regular basis if you can,” Dr. Rafael Pelayo, a sleep specialist at Stanford Health Care in California, told Healthline.

“A real clue whether you’re getting enough sleep or not is based on what you do on weekends. If somebody is sleeping in on a weekend routinely… and they’re trying to catch up on sleep, obviously they’re sleep-deprived during the week,” he said.

The number of hours of necessary sleep can vary based on age.

“For most adults, 7 to 8 hours is optimal, while 9 hours is required for adolescents, 10 hours for middle schoolers, 11 hours for elementary schoolers, 12 hours for toddlers (1 to 3 years old), 14 to 15 hours for infants, and 16 to 20 hours for neonates. These times are for a 24-hour period, so this includes daytime naps,” Dr. Richard Castriotta, FCCP, FAASM, sleep medicine specialist and pulmonologist at Keck School of Medicine of USC in California, told Healthline.

Castriotta said it’s not just the hours spent sleeping that can matter, but also the consistency of sleeping patterns.

“The healthiest sleep is to have a regular bedtime and wake-up time,” he explained. “Circadian rhythm disruption will cause problems, as anyone who’s ever experienced jet lag will confirm.”

“Also, shift work with a night-time work schedule is considered by the WHO as ‘probably carcinogenic’ with increased incidence of breast, prostate, and lung cancer, as well as obesity, diabetes, cardiovascular disease, stroke, and miscarriages,” Castriotta said.

The authors of the current study found an association between poor or variable sleep and higher BMI, but the reason behind this remains unclear.

Pelayo said there are a few theories.

“One thinking is that people are staying up late and eating late at night because they have more time to eat and that may be a factor. Also people who are tired may be eating to keep themselves awake and then just not getting adequate sleep,” he said.

Impulsive behaviors may also play a role in snacking or overeating.

“We know that when people don’t get enough sleep they tend to become more impulsive. To the brain, if you’re not getting enough sleep… when you’re keeping yourself awake it means to the brain something is wrong and if something is wrong the brain is wired to take chances,” he said.

“So there’s a shifting in how we do things. There’s an actual imbalance that can be measured where we overvalue the rewards and undervalue the risks when we’re sleep-deprived,” Pelayo added.

A higher BMI is just one of the consequences that can occur due to poor sleep.

Prior research has found a link between poor sleep and hypertension, obesity, coronary artery disease, type 2 diabetes, and incident pneumonia.

“On the extreme, you can die. At the most basic level, people who don’t get enough sleep have shorter life spans to some degree,” Pelayo said.

“We now know that the amount of sleep you get influences your immune response,” he added. “If you sleep deprive somebody, they’re more likely to get a virus or an infection and also they won’t respond as well to immunizations.”

“Anything that is wrong with you physically or psychologically is made worse by lack of sleep,” Pelayo continued. “For example, if you’re prone to migraine, you’ll have worse migraine if you don’t get enough sleep. Anything you can think of is made worse by not getting enough sleep.”

Experts say it’s important to have healthy habits surrounding sleep.

“Have a regular time for bed, with relaxation a couple of hours beforehand, and a consistent wake time (including weekends). Avoid vigorous exercise, bright white light, or any level of blue light (including smartphones, tablets, computers, TV, etc.) before bedtime or during the night after waking up,” Castriotta said.

“Avoid excess caffeine anytime and alcohol before bedtime. A warm bath or shower taken 1 to 2 hours before bedtime will improve sleep. Be sure the bedroom is cool and comfortable,” he added.

Pelayo said sleep is the ultimate form of self-care and should be prioritized.

“The most important thing we can do is make sleep a priority in our lives. Think about it. Do you view sleep as an inconvenience? Or is it something that is worthwhile? Do you find value in sleeping?” he said.

“First figure out how many hours [of] sleep you’re going to sleep, reserve that time, and then we have the rest of the day to do whatever we want to do,” he added. “But you can’t do the opposite, like ‘I’ll sleep whenever I have time.’ You can do that short term in a crisis situation, but it’s not a good way to live your life.”