In this work, we present a transit timing variation analysis for 20 hot Jupiter systems, which we interpret with theoretical tidal dissipation models. For the majority of the sample, we conclude that a constant orbital period model represents the timing data best. Only WASP-12 b, TrES-1 b and WASP-121 b exhibit a changing orbital period, according to the most up-to-date results. We updated the orbital decay rate of WASP-12 b to P=-29.4 +/- 4.0msyr-1 and the corresponding stellar tidal quality factor to Q & lowast;'=1.72 +/- 0.18 & times;105 . For TrES-1 b, the median quadratic model suggests a period decrease at a rate of -14.9 +/- 0.6 ms yr-1, but the corresponding Q & lowast;'=570 +/- 60 does not agree with the theoretical estimates, which suggest Q & lowast;"'similar to 106 due to internal gravity wave dissipation. Lastly, WASP-121 b exhibits orbital growth at a rate of 15.1 +/- 0.8 ms yr-1, and theoretical results support outward migration due to strong inertial wave dissipation."