The definitive OTP ( Off-The-Peg ) List (<£500 and <£1,000 sections)

But you would feel the benefit of a lighter bike if you lost some weight first. I'm just going on my own experience. I had bmi of 34 a year ago and my bike was 25lbs in weight. So I was advised to lose some weight first then get a lighter bike later as I would feel the benefit then. My bmi is now 19. So I am now looking for a lighter bike or to make my current road bike lighter. On the other hand if it makes someone feel good to have the lightest bike in town then go for it. It wont make you any better up hills though.

It will actually make you faster up hills (as would any reduction in weight anywhere). Just not enough to notice!

The nice thing about a light bike is the handling (direction changes, hopping over things etc,.).
Also, saving 4 kg on bike weight will feel noticeably different/better than saving 4 kg on body weight.