Effects of Prolonged Use of Extremely Low-Fat Diet on an Adult Human Subject

Abstract

An adult human subject was maintained for a period of 6 months on a nearly fat-free diet (less than 0.03 gm. of fat per kilogram of body weight per day) without demonstrable harm. Young rats placed on the same diet developed the typical fat deficiency syndrome. The only objective clinical effects of the diet on the adult human subject were a) a gradual loss of body weight during the first 3 months from 69 to 62 kg. and b) a coincident reduction to normal of a slightly elevated arterial blood pressure. Subjectively the most striking effects were, a) disappearance of a previously experienced feeling of fatigue at the end of the day's work and b) disappearance of recurrent attacks of migraine-like headache from which the subject had suffered for some years prior to the time of the present experiment. The respiratory quotient following a large meal of the experimental diet rose to 1.04, 1.11 and finally to 1.14 on different occasions during the sixth month of the low-fat dietary period; whereas under identical conditions before and after the period, it never rose above 0.97 and 0.99 respectively. In this respect the effect of the diet on the human subject is the same as that in the rat. Repeated determinations of the basal metabolic rate before and after the experimental period gave values varying between -9 and -12%, whereas during the sixth month of the low-fat dietary period it was -2. The iodine number of the total fatty acids of the serum from fasting blood specimens was decreased from an average of 123 before the special dietary period to an average of 93 during the period. At the same time the linoleic acid of the serum was found to have fallen from 5.7 to 3.2% of the total fatty acids and arachidonic acid from 3.2 to 1.8%. These changes in the serum fatty acids are similar to those found in rats suffering from the use of diets deficient in unsaturated fatty acids (Hansen and Burr, '33) and in human infants suffering from eczema (Hansen, '33, '37; Brown and Hansen, '37). Decrease in the unsaturated fatty acids as a result of the low-fat regimen indicates the probability that even the normal adult human subject, like the rat, is unable to fabricate the highly unsaturated fatty acids, which should, therefore, be provided in the diet. In the light of this latter observation, it cannot be assumed that the human subject could subsist indefinitely on a diet completely devoid of the unsaturated fatty acids.