Originally Posted by cubewheels

A heavy bike isn't that harder to pedal than lightweight bike unless you're dealing with lots of climbs.

In the flats, aerodynamics and rolling resistance of the tires would matter more than weight and if you cruise at >18 mph

So if you live in the flats, you can go with lightweight bike and if you like extra workout, just wear loose shirt or jacket that flaps and balloons like a small parachute in the wind! You can also use low TPI touring tires for even more resistance (and those tires last very long!)