Paper summary: too little sleep makes hungry!

Short Sleep Duration Is Associated with Reduced Leptin, Elevated Ghrelin, and Increased Body Mass Index

What are Ghrelin and Leptin?

Both Ghrelin and Leptin are hormones that influence appetite in humans. Both have a variety of functions, but for the summary here the following are important:

  • Ghrelin gets secreted when the stomach is empty and signals hunger to the brain. It also prepares the body for food consumption by increasing gastric acid secretion and helping the stomach to distend more easily. It interacts with part of the brain’s reward system too, making consumption of good food and alcohol rewarding.
  • Leptin plays a role in the storage of fat in the body. It is also what signals the body to stop eating by suppressing some neurotransmitters which stimulate hunger and promoting others which lead to a feeling of satiety.

What is the paper about?

This is a about a long-term study on sleep disorders called the Wisconsin Sleep Cohort Study. It includes about 1000 volunteers and started in 1989. Sleep duration was mostly self-reported by the volunteers through a diary and questionnaires. However, every 5, later 4, years roughly 50% of them accepted to get their sleep measured in the lab for a night. In the morning after, their blood plasma was collected and measured for various hormones including Ghrelin.

If you care about the nitty gritty details, go read the paper. Otherwise here are my takeaways from it:

  • “Short sleep duration was associated with decreased Leptin and increased Ghrelin, changes that have also been observed in reaction to food restriction and weight loss and are typically associated with increased appetite.” – Too little sleep makes hungry.
  • “Elevated Ghrelin mainly correlated with acute sleep loss as measured by polysomnography immediately prior to blood sampling, while reduced leptin correlated with chronic sleep restriction indicated by self-reported sleep measures.” – One night’s loss of sleep makes you hungry, but continuously sleeping too little prevents you from feeling full.
  • Less sleep is worse for your body mass index (BMI) than too much, but both are correlated with higher BMI. The paper suggests higher Ghrelin levels as a mechanism for the “too little sleep” part. The sleep time correlated most with lowest BMI is 7h 40 min. This is, however, also the lower limit of sleep.

Take this with a grain of salt, as I am no expert on the topic.

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