Kelly West rediscovers the high carbohydrate diet and Himsworth's results, and then the fear of saturated fat pushes the ADA to accept the high carb/ low fat recommendations popular at the time. Read his fascinating review of the science in 1973 which are balanced despite their support of carbohydrate.
Diet therapy of diabetes: an analysis of failure by Kelly M West
Kelly West, among others, rediscovered the high carbohydrate diet in the 1960s. He was astonished to discover when writing up his results that ‘very similar experiments had been done by Himsworth, with the same results. Over and over again this phenomenon has been rediscovered—and subsequently forgotten or disregarded’ . Even those who remained unconvinced as to the virtue of a high carbohydrate diet were persuaded of the need to reduce fat, and the new diet was greeted with particular enthusiasm by those who had rediscovered that a high fat intake might be bad for the heart. Concerns about ‘diet heart’ powered many investigations into the virtues of polyunsaturated fats and fish oils , and the new high carbohydrate/low fat recommendations were formally recognised by the ADA in 1971 .
"A review of the available evidence shows clearly the rarity with which diabetics understand and follow their diet prescriptions. The reasons for these shortcomings and their persistence are many and complex. They include the tendency of physicians to underestimate the formidability of developing, implementing, and adjusting a diet prescription that is both acceptable and effective over a long period of time. Another problem is the limited conceptual and technical knowledge of most physicians concerning dietary principles, strategies, and tactics as they apply to the various types of diabetes. Recent research confirms the important potentials of diet regulation in mitigating diabetes and its complications. But apparently much of our effort in diet counseling is ineffective and wasteful. It seems desirable, therefore, to review in some detail the reasons for this failure and then to use candid appraisals for developing more effective approaches in the diet therapy of diabetes.