Research doesn't show a clear or consistent link between lack of sleep and changes in stress hormones like cortisol. This means the body's stress response to not sleeping enough varies a lot from person to person or depends heavily on how the study is set up, rather than following a predictable pattern.

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.

It's not just the lack of sleep that makes you hungrier and lowers your leptin hormone; it's actually the stress your body feels from losing sleep that causes these changes. This means managing stress might be more important for weight control than just focusing on sleep duration alone.