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Comment by strken | Hacker News Reader

The "science" in the linked WaPo article, and the science from the journal, weakly indicate that if you get 5 hours of sleep each night for an entire work week you will get fat, and sleeping in for an extra hour on the weekend won't stop you getting even more fat when you do the same thing on Monday and Tuesday.

This has almost nothing to do with what ferros said. No, resting on the weekend won't uneat or burn the extra calories, in the same way that it won't rewrite all your bad code or help your fuzzy memory, but it could very well help you perform at a more normal level the next week.

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How does sleeping less make you fat? Eating more will make you fat, eating less will make you less fat. If you sleep less you have more time to eat more, but that still requires the eating to happen.

Sleep deprivation causes overeating.

Towards the end of the book The Hungry Brain, by Guyenet, there's a reference to research where both the sleep deprived group and the control group are let loose in the city and allowed to eat whatever they wanted, conditioned on letting the researchers weight and classify it first.

On average, the sleep deprived group ate around 300 calories more.

(sorry I can't produce the original reference, I don't have the book with me)

From my understanding on this topic, the problem has more to do with insulin sensitivity. It has been measured that insulin sensitivity is worse the day after a poor night's sleep and insulin resistance can help drive fat accumulation, all other things being equal.

Sleep deprivation makes you hungrier, increases your appetite and cravings, gives you headaches and makes you feel miserable if you don't eat more.

The mechanism that drives this are the hormones ghrelin and leptin. Look up their action if you're interested.

"Calories in" is only part of the equation. Sleep metabolism is different from waking metabolism.

Also, to your point, very few people spend their sleeping hours eating. You could eat 1500 calories for every meal and be very lithe - if you slept 23 hours a day. By contrast, it seems anecdotally that people who get less sleep tend to eat more food and more of it is unhealthy: late night Taco Bell, delivery when you're pulling an all-nighter, etc.

Best diet pill on the market? Unisom.

> You could eat 1500 calories for every meal and be very lithe - if you slept 23 hours a day.

Not sure if this statement is sound, for the average person.

If you ate 4500 per day, spread across 3, 20 minute meals, and spent the remaining 23 hours sleeping... your energy expenditure would be minimal, whilst your energy intake large. The average person would gain weight rapidly. (300lb athletes perhaps not, but these are outliers).

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