The risk of obesity increases by 9% for each 1-hour decrease in sleep duration
Good quality sleep often alludes us, and poor sleep leads to various health problems (WebMD) such as heart disease, heart attack, heart failure, irregular heartbeat, high blood pressure, stroke and diabetes.
Here's what you need to know to optimise your sleep duration and to minimise the risk of sleep-related obesity.
Over nearly two decades, sleep has been increasingly recognised as a potential risk for obesity. For example, many observational studies have shown links between short sleep duration and weight gain.
However, a recent study which sought to validate such prior studies found the evidence to be inconclusive. Despite the findings of the recent survey, there are plausible associations between good health and too little or too much sleep which are essential to know.
Sleep and obesity research is a hodgepodge
In 2019 a study in Sleep and Breathing - "Experimental sleep restriction effect on adult body weight: a meta-analysis" - found that the evidence that shorter sleep as associated with obesity was inconclusive. The authors pulled together studies going right back to 2005.
They concluded: "This review cannot support the hypothesis from observational studies that short sleep leads to weight gain".
That was a surprising finding, as the majority of research reports had found a positive association between less sleep and weight gain.
It feels like sleep would make a difference, more studies
To be honest, I found this large (2010) study in Japan to be more compelling than the 2019 study quoted above. The 2019 review examined 15 years of research, but ultimately only six experimental studies were found to be comparable, with a total of 275 adult participants.
The Japanese study included 35,247 participants measured at a baseline and one-year follow-up. In common with many sleep studies, the fact that sleep times and quality were self-reported diminished the value of the quantitative analysis.
Nevertheless the findings are worth knowing, given the high number of participants.
Researchers found that:
Another large Japanese study divided 21,469 participants into four groups according to their self-reported average nightly sleep duration: less than 5 hours, 6, 7, and more than 8 hours.
Individuals who slept less than 5 hours were found to be more likely to experience weight gain. (This was after accounting for differences in age, gender, alcohol consumption, current smoking, past medical history, and level of physical activity.)
Interestingly, this study found no relationship between those who slept more than 8 hours and those sleeping 7 hours. The conclusion:"short sleep (≤5 hours) is significantly associated with weight gain and obesity in both male and female adults".
The time it takes you to get to sleep matters
A 2012 study of 21,148 participants found that variability of sleep duration was associated with weight gain - "the variability of sleep duration is related to body weight gain. Maintaining a constant sleep duration may be recommended for controlling body weight."
Another 2019 study from China quantified the risk of too little or too much sleep. This study found the lowest risk at 7–8-hours sleep per day.
Compared with 7-h sleep duration per day, researchers found the "pooled relative risks" for obesity were:
That is, short sleep duration significantly increased the risk of obesity. Compared with 7-hour sleep duration per day, the risk of obesity increases by 9% for each 1-hour decrease in sleep duration. This "relative risk factor" is compound, meaning for people sleeping 2-hours less than seven hours per day the risk is 19% (1.09*1.09).
Perhaps a good wrap-up is a 2020 study of the relationship between sleep quality and diet quality. Researchers found a positive association (among 500 participants) between low sleep quality and greater food intake of a lower‐quality diet.
People who took longer to drop off to sleep - more than 60 minutes - choose foods with more unsaturated fats, fewer grains, and more sugar than those who dropped off in less than 15 minutes.
Three solid recommendations
Everyone is different.
However, from a broad population perspective, it seems that to benefit most from our sleep, and to reduce the potential risks of weight gain, we should pay attention to these three key factors:
Here are some "Healthy Sleep Tips", and Twelve Simple Tips to Improve Your Sleep, from the Division of Sleep Medicine at Harvard Medical School, and "Strategies to promote better sleep in these uncertain times" Suzanne Bertisch, MD, MPH on Harvard Health.
Wishing you a good night's sleep
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