Amyloid fibrillation is the process of native soluble proteins misfolding into insoluble fibrils comprising of cross-â-sheets and has received wide attention due to its substantial physiological relevance and the complexity of the underlying physical and chemical reactions. At present, more than 20 amyloidogenic diseases including Alzheimer's disease, Parkinson's disease, and prion–associated encephalopathies have been found to share fibril formation as the common cause. Here, we investigate the influence of dissolved osmolytes (sugars) on the kinetics of insulin fibrillation. In the presence of sugars, the fibrillation process (both the lag-time and the rate constant to form fibrils) is delayed and appears to correlate with the heats of solution at infinite dilution thereby supporting a preferential exclusion mechanism. With the recent focus on circular protofibrils and the suspicion that they may be toxic during amyloidosis, we have conducted a series of exploratory experiments during the lag phase when protofibrils are thought to be formed. This has included the use of small angle neutron scattering, sucrose gradient centrifugation, and cryo-electron microscopy to investigate the kinetics of protofibrils formation. We also present a mathematical mechanistic model that simulates the phenomena by incorporating the physical chemistry of nucleation and growth dynamics. Estimated by nonlinear least square algorithms, we find rate constants that account for the ubiquitous sigmoidal responses of amyloidogenic proteins when they misfold.