I avoid talking about weight in the clinic, because it is usually something that get's "noised": one-variable that is not independently an indicator of anything, And even when it is taken in context, that discussion gets moved by people who misunderstand the context.
Weight moves day to day because of hydration, riders' internal plumbing, body's stress reactions to racing and fluid retention, sodium intake, heat/humidity of the day, blood bags, being too road-rashed/crash-broken to eat enough... lots of things.
When people talk about weight, they talk about their good day. Not the day they ate to much steak and were backed-up that morning. That someone's actual weight moves 2 kgs. is not an indicator of deception. And while it is an important issue for calculating power we're going to be asking to weigh each rider's *** every morning to get an accurate power estimate.
In a different vain, listening to riders (and any athlete) talk about weight is the biggest indication that athletes have no idea what they are doing to their bodies, fitness, nutrition, drugs, or otherwise. Athletes can be on a different planet when it comes to making rational decisions about nutrition. Put another way, science cannot investigate the strategies used by athletes because they are so absurd and ridiculous that they would not get by an ethics review for the study.
My point is, don't even take what an athlete says about their nutrition/weight with a grain of salt.