In Dragon Block C there is a red health bar on the right side of the screen. This bar acts as a damage buffer between your health and enemy attacks, basically it is extra health. Damage from DBC mobs will subtract from this only, but other minecraft mobs will subtract damage from your health directly. The mod tries to fix this by immediately subtracting the damage from the extended health bar and healing your minecraft character, but sometimes it will miss the attack and your normal health will take damage. The value of your body attribute acts as the amount of health or half-hearts that this bar can buffer at its maximum.
Once the body value represented by the bar reaches 0, any damage received by the player is subtracted from the normal health and the player will die.
The regeneration of this bar and the minecraft health regeneration are separate.