Length of sleep time and percentage of general sleep in the different sleep stages are linked to an increase in hunger and intake of calories from fat and carbohydrates, as well as a decrease in metabolic rate. This may account for the link between obesity and sleep problems, according to researchers from St. Luke’s-Roosevelt Hospital and Columbia University.

It has been long known that sleep and diet are closely linked. A 2006 study said that sleep is more important in maintaining weight than diet, while a 2007 study suggested that those who do not get enough sleep are less likely to prepare their own food, making them more likely to eat fast food.

The experts looked into how sleep habits affect hunger, in order to determine whether different sleep stages, rather than the time spent sleeping, can alter food habits in healthy adults, including appetite and cravings.

The randomized trial, published in the American Journal of Physiology – Regulatory, Integrative, and Comparative Physiology, was conducted in a laboratory by researcher Ari Shechter and team, involving 27 healthy 30 to 45 year olds. The individuals were subjected to 2 six-day sessions of being monitored:

  • “Habitual sleep” phase – patients were able to sleep 9 hours
  • “Short sleep” phase – patients were able to sleep 4 hours

The phases were 4 weeks apart, in order to leave time for full recovery from the short sleep phase and to make certain that women were on the same part of their menstrual cycle under each sleep state.

Experts utilized polysomnographic recording to analyze sleep structure and length of sleep time. Time spent sleeping in stage 1, stage 2, slow wave sleep (stages 3 and 4), and REM sleep was calculated and demonstrated in minutes and as a percentage of the total time spent sleeping.

During the first 4 days, the individuals were given meals which were adjusted to match the energy needs to maintain weight. On the fourth day, the people were asked about how hungry they felt and their level of desire for certain foods.

The researchers calculated RMR (resting metabolic rate) on the fifth day, when the participants were in a fasted state, and the volunteers were then able to eat what they wished during the last two days.

The experts examined the difference between the individuals’ sleep habits during short sleep and habitual sleep phases, and the association between sleep habits, RMR, appetite, and food intake.

They discovered that the short sleep phase lead to less time spent sleeping in stage 2 and REM, as well as more total time spent sleeping in slow wave sleep stage, when compared to habitual sleep.

These alterations were partly due to decreased RMR, a jump in feelings of hunger, and an increase in the amount of calories, carbohydrates, and fats among the participants. In particular, there was a clear link between stage 2 sleep length and RMR, and an inverse relationship between stage 2 sleep percentage and calorie intake.

There was also an inverse relationship found among REM sleep duration and hunger among the participants, and an inverse relationship between cravings for salty and sweet food and the amount of time spent sleeping in stage 2.

Higher intake of fats and carbohydrates was linked to lower percentage of REM sleep time and slow wave sleep.

The findings of the study reiterate the fact that length of sleep is clearly important. However, they also demonstrate that the percentage of time spent in each stage plays a significant part in the correlation between obesity and sleep.

Shechter concluded:

“Any number of various factors like obstructive sleep apnea, certain drugs/medications, chronic exposure to short sleep duration, shift work, jet lag, and changes in the scheduling of the sleep episode, can affect sleep stage quantity and distribution. Our data may provide an explanation for the greater obesity prevalence observed within some of these conditions.”

Written by Christine Kearney