I must say that I have never seen a -700 exceed max zero fuel weight, but if it was a -300 it is very possible. For example :
Typical easyJet -300 : MZFW = 47627kg
DOW = 33375kg
Allowable traffic load = 14252kg
Say a full flight, heavy on males :
90 Males @ 93 kg = 8370kg
59 Females @ 75kg = 4425kg
120 Bags @13kg = 1560kg
Total = 14355kg
So it can and does happen, although infrequently.