Riding a light bike makes a huge difference. I used to have a bike which weighed 10,5kgs before I went on a weight rampage, after it was finished it weighed around 8,3kgs. That's over 2kgs gone and on the first ride it felt like the bike doesn't weigh anything. For people who are wrong and think that weight doesn't make a difference, try strapping some ankle weights (lets say 1kg on each leg) and jumping around. You will feel strangely heavy.