i know axle shed a lot when he lost his puppy coat, and then he also sheds to get his summer coat and then again to get his winter coat. when he blew his puppy coat OMG, you could have made 4 dogs out of all the hair i swept up. you could try bringing him to the groomer and asking them to "blow him out" and see if that helps. some groomers have a giant vacuum that blows OUT and gets all the loose hair that's falling out off of them. it's really nice in the bad shedding times lol
anywho, i'm sure it's normal shedding, and you're just noticing it. BUT, if it gets outrageously horrible with bald spots or overly thinning hair, with him having weight concerns on top of it i would ask my vet. it can't do any harm to ask. esp. if it's super bad or worries you, as it could be related if in fact it is a medical problem.