This usually occurs more often with males. They may have toned, bulging arms and appear to work out regularly, but beneath that tight white t-shirt they often favour is nothing but a rather round little pot belly and non-existent pecs.
Flab packs cause regular disappointment to 'totty spotters' on the beach.
Also known as 'fake packs'.
Girl 2: He's taking of his shirt...
Girl 1: *sighs* Just another flab pack.
Dude: Nah man don't be deceived by the flabpack. Soft as as a bowl of jelly under this tee, but hey thats between me and you ;P