Sleeping in on weekends doesn't make up for a short week of sleep
'I'll lose sleep during the week and catch up on weekends' sounds like simple bookkeeping — miss some hours, add them back later, balance restored. But research on chronic sleep deprivation shows it doesn't work as cleanly as hours-in, hours-out math.
Even if total weekly sleep evens out thanks to long lie-ins on Saturday and Sunday, the things that suffer from short sleep during the week — attention, insulin sensitivity, appetite hormone balance — don't fully or immediately bounce back. Some studies find two days of extra sleep on the weekend do improve certain markers, but don't return them to the baseline of someone who slept enough all week.
On top of that, a sharp shift in sleep schedule on weekends (going to bed and waking up much later than usual) creates an effect similar to jet lag — the body has to re-sync its circadian rhythm on Monday, which further drags down productivity at the start of the week. A more durable strategy is aiming for a stable, adequate amount of sleep every night rather than counting on a weekend fix.