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Comment by lmilcin | Hacker News Reader

I am pretty sure that not sleeping at all also increases fat burning as body uses less energy when asleep

The fat burning might be from reaction of organism that is not used to a lot of daily caffeine ingestion. For example, when I don't use caffeine for a long time my heart rate increases when I increase amount of coffee I drink. But then goes back after some time (presumably when my body gets accustomed to it again).

Also, this kind of research must be read with a little bit of scientific background.

It is easy to get an impression author wanted to establish causation, but in reality this research only shows correlation, and correlation does not prove causation.

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> I am pretty sure that not sleeping at all also increases fat burning as body uses less energy when asleep

From the admittedly little I know about biology and sleep science; I thought it was universally accepted that poor sleep harms your metabolism and thus would make fat-burning less likely.

No, it is not "universally accepted".

It is actually opposite. Most organisms under stress increase their energy consumption.

A good proxy for energy consumption by your body is your heart rate. Heart rate is linked to the amount of blood distributed through your body and amount of blood is amount of oxygen that is needed by your cells for metabolism.

And amount of oxygen used by cells is almost equal to the amount of energy produced (excluding those rare anaerobic regimes).

Heart rate is always lowest at night during sleep.

What you probably meant is that a person who has poor sleep will have a statistical tendency to eat more, for many reasons. One it is more difficult to exercise willpower when you are not rested well. It might also be more difficult to accurately judge whether what you feel is hunger.

To accurately compare energy use by body you would have to externally limit amount of calories ingested to same level and figure out how much CO2 you emit or how much weight you lost.

Otherwise you are measuring your regulating machine -- ie. your brain, hormones, etc. and that is whole other set of problems.

Eating makes us feel better and if you are on poor sleep you might eat just to offset it.

I’m quite sure you’re mistaken as studied animals (usually rodents) do not behave the same as humans; and ultimately if our metabolic system becomes unbalanced then our body is suffering and will certainly attempt to overcompensate or risk damaging itself.

It matters very little if we burn fat faster, though I doubt it; it matters what the outcome is. In this case it does appear that people get fatter.

> More than two dozen epidemiological studies from around the globe looking at sleep deprivation and BMI in humans have shown association between decreased obesity and an increase in sleep duration.

> Data regarding impact of sleep deprivation on weight loss is conflicting in animals and humans. Sleep deprivation in rodent models causes weight loss despite hyperphagia [63–68]. These differences in rodents and humans may be explained by increased brown fat in rodents (rarely present in adult humans), which is metabolically more active and has been shown to increase thermogenesis and total energy expenditure [67]. In conclusion, epidemiological data is suggestive of weight gain with sleep deprivation though a few studies have also noted weight gain with prolonged sleep. Based on data on sleep duration and weight, sleep hygiene counseling could form an important tool in management of obesity.

https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2929498/

I don't see how this contradicts GP points.

The first point is that lack of sleep is associated with increased metabolism (increased energy expenditure at rest).

The second point is that the apparent link between weight gain and sleep deprivation could be explained by involontary caloric intake increase.

You left out the next part of your first quote:

> More than two dozen epidemiological studies from around the globe looking at sleep deprivation and BMI in humans have shown association between decreased obesity and an increase in sleep duration. These studies however do not establish a causal relationship.

The paper also mentions and agrees with who you were responding to:

> In summary, energy expenditure is reduced during sleep. Sleep deprivation appears to increase energy expenditure.

And finally in the conclusion:

> Paradoxically a similar U-shaped relation is also noted in several studies looking at the relationship between sleep and weight, with both short and long sleep leading to weight gain.

I may have missed it, but it doesn't appear a causal relationship was ever formed between metabolic dysregluation from sleep issues and weight gain. And since both less and more sleep were associated with weight gain, is sleep or the lack thereof just another symptom of stress and depression? Both of which often cause people to eat more.

A lack of sleep leads to higher levels of cortisol and insulin, and decreases insulin sensitivity. This in turn physically prevents you from burning stored fat and leads to blood sugar being converted into fat for longer-term storage.

[1] https://www.sleepfoundation.org/physical-health/sleep-and-bl...

Poor sleep is associated with weight gain.

I wonder if that’s because sleepiness is associated with poor impulse control. I know when I’m super tired I tend to eat whatever I want the next day.

That and you may be having an extra meal whereas you otherwise would have been asleep.

There is that and there is the “enforced fasting interval” that sleep is.

The first meal after sleeping through the night is called "break-fast", after all.

it's because sleep regulates the hormones that control your appetite

if you mean poor control of your body's natural drive to eat which is imperative to our survival, then sure

very few people can consistently control this "impulse" -- the best way to control it is to get adequate sleep and regulate your hormones

One means to keep functioning while sleep deprived is to eat more. I don't think it's really poor impulse control per se. It's a coping mechanism, sort of like the body shunting waste gas through the kidneys at high altitude because you can't offload them all via breathing out and they have to go somewhere, but that's not really the optimal way to do that and it has knock on effects because urinating to remove them also drags salt and other stuff with it, thus the need to drink more and get more electrolytes at altitude. (Edit: implicitly, weight gain us the equivalent knock on effect for eating more while sleep deprived.)

The sleep deprived body directs calories to fat storage.

See my other response to sibling comment.

TLDR: weight gain is not from body using less energy but from your regulating machine being put out of balance.

Body on caffeine will still use more calories, but your brain on poor sleep will make worse choices and you will eat more just to offset unhappiness.

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