When healthy young men don't get enough sleep for a few nights, their stress hormone (cortisol) actually goes down—but their blood sugar control gets worse. This suggests that something other than stress hormones is causing the metabolic problems.

If you only get four hours of sleep for four nights in a row, your body becomes less able to handle sugar properly—worse than just pulling one all-nighter. This means chronic sleep loss might be more harmful to your metabolism than a single night without sleep.

If you don't get enough sleep for a few nights, your body might start having trouble managing blood sugar, causing insulin levels to rise. But if you stay up all night instead, it doesn't have the same effect—so it's the ongoing lack of sleep, not just one bad night, that seems to mess with your insulin.

If you don't get enough sleep for a few nights in a row, your body becomes less efficient at using sugar for energy—but if you stay up all night just once, it doesn't have the same effect. Missing sleep over time is worse for your blood sugar than one all-nighter.

Staying awake all at once doesn't actually change your stress hormones, blood pressure, or heart rate the next day if you're a healthy young adult in a relaxed setting. This means that just losing a night of sleep won't automatically spike your body's stress response unless you're also under other pressures.

Not getting enough sleep over a long period can make your body less effective at processing sugar, which might raise your chances of developing type 2 diabetes and other metabolic problems.