Lack of Sleep: Weight Loss, Fat Gain, Hormonal Issues

lack of sleep

For many of us, going to bed later than usual has become so commonplace that we do not pay attention to it. We try to compensate for the lack of sleep on weekdays by sleeping on weekends.

Especially young people, who use the Internet for rest, “sin” by practicing sleep deprivation over and over again. At night instead of sleep, they watch movies, play video games, communicate on social networks. Unfortunately, getting enough sleep for them is impossible, therefore, whatever the reason for the sleep deprivation, its result is obsessive drowsiness. And when sleep deprivation becomes a chronic occurrence in our lives, it’s time to sound the alarm.

Sleepiness can bring us down at work, school, damage relationships, cause sudden outbursts of anger and depression, and even pose a threat to life. People who neglect adequate sleep often complain that they feel as if they are in a fog, that they have a bad headache, etc.

Let’s figure out what problems await someone who ignores the need for good sleep!

How Does Lack of Sleep Affect Excess Weight?

sleep deprivation

Lack of sleep leads to excess weight

People who stay up late and wake up late gain weight more easily than people who go to bed early and get up early. This follows from a small human study published by neuroscientists at Northwestern University in the journal Obesity.

Lack of sleep leads to an increase in fat mass, moreover, there is evidence that it also leads to a decrease in muscle mass. However, less is known about sleep patterns and overweight.

Some go to bed late and get up late, and those who go to bed early and like to get up early. So which of these types is the easiest to gain weight?

The researchers aimed to answer this question. They studied 52 people, ages 18 to 71, and tracked the participants’ daily rhythm for seven days. The subjects recorded what, how much, and when they ate.

Study: weight gain – sleep deprivation link

Just over half of the participants fell into the early bird category, going to bed at 12:30 am on average and waking up at 8:10 am getting six and a half hours of sleep in 24 hours. Fewer than half of the participants were night owls who did not fall asleep until 3:45 am and wake up at 10:45 am, so the average night owl slept for about five and a half hours every 24 hours.

According to the table below, night owls ate 248 kcal more than early birds in 24 hours. In addition, night owls ate less healthy foods. They drank more sugar-filled soft drinks, ate more fast foods, and consumed fewer fruits and vegetables, so it’s no surprise that late-night party lovers were fatter than early birds. The average early bird had a BMI of 23.7, the average night owl had a BMI of 26.0.

study sleep
study obesity

When the researchers analyzed their data statistically, they found that less sleep in night owls was not responsible for the overeating effect. Rather, it is the habit of night owls to eat extra at night, which seems to cause overeating.

Sleep affects weight loss

Human circadian rhythms in sleep and metabolism are synchronized with the daily rotation of the earth, so when the sun goes down you have to sleep, not eat,” study leader Phyllis Zee said in a Northwestern University press release about the publication.

When sleep and nutrition do not match the body’s internal clock, it can lead to changes in appetite and metabolism, which can lead to weight gain.” 

According to Zee, the results of the study are relevant not only for people who want to lose weight but also for people who work night shifts.

“It’s midnight now, but they’re having lunch. They have a higher risk of obesity, as well as cardiovascular, cerebrovascular, and gastrointestinal disorders.”


  1. Role of Sleep Timing in Caloric Intake and BMI. Kelly G. Baron. Obesity (Silver Spring). 2011 Jul;19(7):1374-81.
  2. 11 Effects of Sleep Deprivation on Your Body – HealthLine 

Lack of Sleep and Hormonal Disbalance

lack of sleep effects

Effect of sleep on testosterone

Older men can double their testosterone levels by simply increasing their sleep time. Such conclusions come from a study that Plamen Penev of the University of Chicago published in the journal Sleep. [1]

Probably almost all of us sleep too little, mainly because modern technology distracts us from sleep every day. They allow us to generate light at night, providing us with 24-hour entertainment and information through electronic media, and also allow us to have contact with each other whenever we want. Every evening, when our body tells us to sleep, we can do a thousand other things during that time.

Lack of sleep causes a decrease in testosterone

Lack of sleep disrupts the hormonal balance. For example, it makes our body less sensitive to insulin. Dutch researchers have previously shown that after just one night of four hours of sleep, the sensitivity of young men to insulin decreased by 20% [2], and in diabetics by 25%. [3]

In the latter case, sleep deprivation has clinical implications, so doctors might advise diabetics who have an inadequate response to their medications to get more sleep.

“Sleep duration could be another therapeutic target for improving glucose regulation in type 1 diabetes,” the Dutch researchers concluded.

Sleep boosts testosterone

Testosterone also depends on the amount of sleep. This is not so strange, since our bodies produce much more testosterone when it is asleep than when it is awake, regardless of the time of day.

“The results show that sleep is a more potent regulator of testosterone than circadian factors.” [4] The graph below shows how much testosterone is present in the blood of 22-32-year-old men during nighttime and daytime sleep and the rest of the day.

testosterone study

Another study found that the better the sleep quality of men, the higher their testosterone levels. That is, the secretion of testosterone is associated with certain phases of sleep. [5]

In the average man over 40 y.o., testosterone levels drop 1-2% per year, but researchers occasionally see men over eighty with testosterone levels that are usually found in younger people.

Add to this the fact that many older men, but not all, sleep less as they get older, then automatically you might think that the scientist Plamen Penev wanted to check in his study: whether testosterone levels in older men decrease, simply because that they sleep less?

Penev based his theory, among other things, on research carried out by Eva Van Couter, a sleep researcher at the University of Chicago who can be called a celebrity in the field of endocrinology. Back in the early 2000s Van Couter discovered that men in their 40s produce less testosterone during sleep than men in their 20s. [6]

Study: How Sleep Boosts Testosterone

lack of sleep headache

Penev measured the amount of testosterone in the blood of 12 slender, healthy, nonsmoking men between the ages of 64 and 74. He also made the men wear a small device on their wrists that allowed him to see how many hours a day the men were sleeping. This figure ranged from 4.5 to 7.5 in 24 hours. The longer the men slept, the more testosterone circulated in their blood.

The men who slept the least had testosterone levels of 200-300 ng/dL. This is a normal amount for men of this age, but this is the lower limit of the norm. The men who slept the most had testosterone levels twice as high: 500-700 ng/dl. This level can be found in healthy young people.

“These data suggest that complaints of poor or insufficient sleep in healthy older men may be associated with more pronounced age-related declines in androgens,” Penev writes.

“Identifying such sleep complaints in the doctor’s office may facilitate a reasonable interpretation of lower testosterone levels in older male patients.”

Before men decide to start testosterone therapy, they can first measure their sleep during the day. And this “dimension” is significantly different from the banal “guessing”. Most people overestimate the number of hours they sleep. This was also the case in Penev’s experiment.

The men believed they slept an average of seven and a quarter hours a day, but Penev’s records showed that they only slept six hours a day.


  1. Middle-Aged Men Secrete Less Testosterone at Night Than Young Healthy Men. Rafael Luboshitzky, Zila Shen-Orr, Paula Herer. Sleep. 2007 Apr;30(4):427-32.
  2. A Single Night of Partial Sleep Deprivation Induces Insulin Resistance in Multiple Metabolic Pathways in Healthy Subjects. Esther Donga, Marieke van Dijk, J. Gert van Dijk, Nienke R. Biermasz. J Clin Endocrinol Metab. 2010 Jun;95(6):2963-8.
  3. Partial Sleep Restriction Decreases Insulin Sensitivity in Type 1 Diabetes. Esther Donga, MD1, Marieke van Dijk. Diabetes Care. 2010 Jul;33(7):1573-7.
  4. Effects of Acutely Displaced Sleep on Testosterone. John Axelsson, Michael Ingre, Torbjörn Åkerstedt. Clin Endocrinol Metab. 2005 Aug;90(8):4530-5.
  5. Disruption of the Nocturnal Testosterone Rhythm by Sleep Fragmentation in Normal Men. Rafael Luboshitzky, Ziva Zabari, Zilla Shen-Orr. J Clin Endocrinol Metab. 2001 Mar;86(3):1134-9
  6. Middle-Aged Men Secrete Less Testosterone at Night Than Young Healthy Men. Rafael Luboshitzky, Zila Shen-Orr, Paula Herer. J Clin Endocrinol Metab. 2003 Jul;88(7):3160-6.
lack of sleep symptoms

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