Sleep helps beat obesity in Korean adolescents


By John DiTraglia



Obesity and sleep deprivation seem to happen together. But remember the old adage – correlation is not causation. That primrose path to wrong was perhaps most recently demonstrated by all the brouhaha about vitamin D and health effects. Stop checking and treating vitamin D levels. (1) And even if it was causal in this case it could be that obesity causes poor sleep rather than the other way around.

This issue would be hard to study in humans since torturing humans is not allowed. But a natural experiment increased sleep duration for adolescents in South Korea. In March 2011, authorities in three of the 16 administrative regions decreed that the closing hours of hagwon (private tutoring institutes) had to be 10 PM. This policy change was associated with sleep extension and body weight reduction in general high school 10th−11th graders whose sleep duration would otherwise have not increased. The main results suggested that a 1-hour increase in sleep duration was associated with a 0.56 kg/m2 reduction in body mass index, a total average body weight reduction of more than 3 and a half pounds and a decreased risk of being overweight or obese by 4.2% points. (2)

Some Korean parents might think that that amount of weight or obesity change is not worth not getting into Harvard. The benefit of Harvard attendance on happiness and richness and longevity might outweigh the modest health and cosmetic benefits of this weight difference. For the rest of us low achieving mortals though, that’s a pretty big thing.

This is the fourth installment about sleep and obesity that we’ve written. The most recently one was this past September 3rd. Maybe that’s enough evidence now to believe that sleep curtailment causes some part of obesity. There are all kinds of other benefits to getting a good sleep. We violate nature’s design for sleeping at our peril. It’s fun and easy to sleep. You just have to get less done or get more efficient.

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By John DiTraglia

1. Lucas A et al. Vitamin D and health outcomes: Then came the randomized clinical trials. JAMA. Published online November 8, 2019. doi:https://doi.org/10.1001/jama.2019.17302

2. Do YK. Causal Effect of Sleep Duration on Body Weight in Adolescents. A Population-based Study Using a Natural Experiment. Epidemiology: November 2019 – Volume 30 – Issue 6 – p 876–884. doi: 10.1097/EDE.0000000000001086. Sleep

1. Lucas A et al. Vitamin D and health outcomes: Then came the randomized clinical trials. JAMA. Published online November 8, 2019. doi:https://doi.org/10.1001/jama.2019.17302

2. Do YK. Causal Effect of Sleep Duration on Body Weight in Adolescents. A Population-based Study Using a Natural Experiment. Epidemiology: November 2019 - Volume 30 - Issue 6 - p 876–884. doi: 10.1097/EDE.0000000000001086. Sleep