Metabolic effect of sleep


Most Australians are sleeping less than they did previously. Some interesting facts from a study done by University of Adelaide in 2016:

  • Average reported sleep time is 7 hours
    • 28% of people report < 6hrs/night
    • 12% sleep less than 5½ hours
      • 76% report day time impairment or sleep-related symptoms
    • People sleeping less than 7hr doubled since 1960
    • 26% of Australians both use the internet most nights just before bed and have frequent sleep difficulties or daytime impairments
    • Lack of sleep has a range of metabolic effects

Effects of Not Enough Sleep

The top 5 effects that happen when we do not get enough sleep are as follows:

  1. Stress sugar effect
    1. Brain needs energy to think. Searches for preferred energy source (glucose)
    2. Because it is deprived of sugar, reduced the control mechanism in the brain. We become more impulsive and search out food
    3. Brain reward system (seeks sugar foods), more active when low blood sugars. Pre frontal cortex that control this is deactivated

    OUTCOME: We are more impulsive to look for sugary foods.

  2. Impaired glucose tolerance and effect when sleep 4-5 hrs/night
    1. Glucose clearance: 40% slower in the sleep-debt condition than in the sleep-recovery condition
    2. Glucose effectiveness: 30% lower in the sleep-debt condition than after the sleep-recovery condition
    3. Insulin response to glucose: 30% lower in the sleep-debt condition than in the deep-recovery condition

    OUTCOME: We are less effective at managing the sugars and that leads to a greater risk of diabetes.

  3. A slowed resting metabolic rate. RMR is the energy required for our body to keep going. That is to keep warm, to think, to break down food.
    1. Sleep deprived for 3 weeks (5.6hr/night) with altered circadian rhythm – 28 hr days
    2. 8% reduction in RMR

    OUTCOME: 8% reduction in RMR equates to a 6kg in weight gain over a 1 year period.

  4. Increased release of Ghrelin
    1. Ghrelin is the hunger hormone
    2. Release by GI tract – controls food intake in dose proportional manner
    3. Significantly increased in sleep deprived state

    OUTCOME: WE are hungrier so we eat more food.

  5. Impaired leptin response
    1. Leptin is the satiety hormone. Release by adipocytes (fat cells)
    2. It increases metabolic rate, physical activity, decreases hunger
    3. 19% reduction in the amount released when sleep deprived

    OUTCOME: WE are hungrier so we eat more food. We need more foods to feel full.