Final answer:
When the production of free radicals outpaces the body's antioxidant defense, oxidative stress occurs and can lead to cellular damage and aging.
Step-by-step explanation:
The situation where the production of free radicals outpaces the body's antioxidant defense occurs when there is an imbalance between the production and neutralization of reactive oxygen species (ROS) in the body. ROS, such as superoxide and hydroxyl radicals, are highly reactive molecules that can cause damage to cellular components including DNA, proteins, and lipids. When the production of ROS exceeds the capacity of the body's antioxidant defense systems, oxidative stress occurs and can lead to cellular damage and aging.