I'm 5' 5" / 165cm, 9st 6lb / 60 kg, and 74 years old, and my leg muscles don't work very well nowadays. I've found lighter bikes are definitely less effort to ride than heavier ones. I need all the help I can get so I will change components for lighter ones whenever I can. The best value for money changes are tyres and saddle. Pedals can also be very heavy. I also carry as little as I can in case of emergencies in a saddle pack, which can easily weigh 600 gms plus.