"POSITIVE: Decreases mass by 30% all the time, resulting in more powerful explosive jumps. NEGATIVE: This perk triples the delay after taking damage before your health regeneration starts. Recommended for advanced players only."
Lightweight reduces the player's weight, allowing them to boost themselves faster, but at the cost of a longer regeneration delay. This is a Secondary Perk.
This perk is primarily used by flag chasers, whose only goal is to retrieve the flag. Most chasers suicide after the flag is secured, so regen is not important to them.