At one time I used to be a real weight weenie.
Reluctantly I will tell you something. I had a carbon fiber fork explode while I was riding about 7 mph through a perfectly smooth parking lot. This dropped me straight face first into the asphalt. My Bell helmet smashed flat and I was knocked unconscious for over 5 minutes. The ambulance took me 25 miles away to an emergency hospital near my home for some reason. Since I was walking and talking at the time they simply released me.
Well I wasn't OK. I have a serious concussion and no short term memory at all. With no short term memory there is nothing to go into long term memory.
I couldn't even remember to eat and start losing weight.
I was also having seizures connected with the concussion of a sort that leave no memory of they having happened. So when I had a seizure behind the wheel I would have a wreck and couldn't report to the police what happened. Luckily there was only one minor injury but the price of my insurance per year was about a third of the cost of a new car. Because of the collisions I was selling my entire bike collection to pay the bills. I threw away all of my large collection of team jerseys and all the other paraphernalia since there was no use for it.
Finally my best friend, a now retired NCIS agent, took matters into his own hands and forced my doctor to refer me to the Palo Alto cancer center since none of the local neurologists could find anything wrong with me and I had lost 42% of my body weight and my GP said that it had to be some sort of cancer they couldn't identify.
The cancer center went over me and said that I was as healthy as a horse except for my weight. The lead on the case suggested a Professor of Neurology at Stanford.
He did ONE simple memory test that took two minutes and with my history pronounced all of the symptoms I was having was because of a concussion. It took him about six months to balance the medications properly and I came awake - two and a half years after my fall.
The moral of this is - most doctors are incompetent except on everyday parts of their practices. Neurologist end up treating mostly aging diseases and cannot identify a BMW from a Ford after a year of that. A large percentage of GP's are simply incompetent period.
It has taken me three years to come back as much as possible but I will never know what happened in those two and a half years and the seizures were accompanied by the destruction of large blocks of, personal and not professional, memory
I now have to take two different medications, that make me feel dizzy, for the rest of my life.
If you believe that 5 lbs of bicycle weight is worth risking that then by all means go for it. And while you're at it keep your flat repair kit in the back pocket of your jersey and keep only one water bottle and that empty so that you can have your friends swoon when they pick up the bike.