Kathleen, Skim cows milk goes bad faster because it is more processed, allowing more degradation and greater possibility of contamination. In nature, untampered with, high fat foods spoil more quickly, as the fats go rancid. Compare whole wheat flour and white flour. That "off" smell in stale whole grain flour or rice is rancid fat. This is why birds eat high fat fruits very quickly when they ripen in the fall, before they spoil, leaving lower fat food sources to be utilized later in the season. So Dr. Lawrence's assertion makes perfect sense in light of these tidbits. Catherine Watson Genna, IBCLC