Here's an example of fetching associated properties in an eagar manner at runtime. Without an HQL query, I don't believe there's anything you can do to dynamically change the FetchType that has been set in a mapping or through a Java Persistence API (JPA) annotation.
from Sale sale
where sale.date > :startDate
left join fetch sale.salesman
left join fetch sale.product
left join fetch sale.product.color
left join fetch sale.product.category