Keen (BrE) and love do not mean the same thing.
Keen is a British English expression meaning enthusiasm for or looking forward to or interest in
He was keen on getting a new dog as a pet.
He was very keen to see The Baggies this weekend.
She is keen to get the house done.
Keen can also mean a an affection for
Johan is very keen on dogs and other animals
He is very keen on the new girl in class
I'm not so keen on malted chips
There are different degrees of keen
Keen is different to fancy (BrE), though both mean attraction towards.
Keen is to running where as fancy is to strolling
She was peckish and fancied a chocolate.
He had a hard day at work and was keen to get down to the pub.
The differences in describing degrees of interest are
Johan is keen on dogs (BrE)
Johan is interested in dogs (AmE)
Johan is a big fan of dogs (AmE)
Johan fancies dogs (BrE)
Johan loves dogs (BrE, AmE)
Johan is a dog-lover (BrE, AmE)
Do you fancy him? (BrE)
Are you in love with him? (AmE)
Do you have a crush on him? (AmE)
Johan is mad about dogs (BrE)
John is crazy about / obsessed with dogs (AmE)