Just to add my 2 cts--I agree with sclim and CoachDave.
From my experience before I even heard of TI, I was carrying about 15 lbs too many. Five days at the gym did nothing to alleviate my excess lbs. I then decided to swim laps for extra exercise. The community I then lived at had a 25m lap pool and was right down the street from me. I swam continuously for almost an hour +, every other day. Total lengths were anywhere from 64 to 75. My form was horrible, my back muscles ached all the time, but I did lose weight.
Now if you truly follow TI, you will do less muscle power and more brain power. You won't lose weight, but you will be a better swimmer.
Choice is up to you.