See the bottom of the page for evidence pyramid explanation.


1. Nedeltcheva et al. (2010). Insufficient sleep undermines dietary efforts to reduce adiposity

  • All 10 overweight adults all ate 90% of their Resting Metabolic Rate in calories per day, which was about 1300 kcal.
  • Every single participant underwent 2 conditions for 2 weeks: sleeping 7.5h per night and sleeping 5.25h per night.
  • In both sleeping conditions they lost 2.9-3 kg. However, 1.5 kg of this was muscle in the 7.5h sleep group, versus a whopping 2.4 kg in the 5.25h sleep group.
  • Limitation: they did not weight train, which may have saved a lot of muscle mass.


2. Scullin et al. (2018). The Effects of Bedtime Writing on Difficulty Falling Asleep: A Polysomnographic Study Comparing To-Do Lists and Completed Activity Lists

  • First study in this area to use polysomnography (brainwave recording) instead of self reported sleeping hours.

  • Active control group that journalled 5 min. about what they had accomplished the past day
  • The alternative hypothesis was that writing a to-do list for the next day will “off-load” those thoughts from consciousness (i.e., Pennebaker-like effects), and thereby make you go to sleep faster.
  • The alternative hypothesis group that spent 5 min. writing a to-do list slept up to 40 min sooner than the other group, and the more detailed their to-do list, the sooner they fell asleep.
  • The key seems that participants wrote down their to-do list rather than mentally ruminating about their unfinished tasks.


3. Viola et al. (2008) Blue-enriched white light in the workplace improves self-reported alertness, performance and sleep quality


Strength of evidence explanation: