The water-suppressed proton NMR spectra of plasma from healthy controls and cancer patients have been recorded along with the high-density lipoprotein (HDL) and triglyceride (TG) levels in the plasma. The dependence of the average of methylene and methyl resonance linewidths on the HDL/TG ratio is demonstrated. It is shown that the deranged lipoprotein levels caused by the presence of cancer lead to the serological test for cancer proposed by Fossel. The work provides the formation for a complete understanding of the proposed serological test for cancer. However, the wide variation in lipoprotein composition in the plasma from both healthy adults and cancer patients means that the serological test proposed by Fossel cannot be used as a screen for cancer.