Response to and range of acceptable fat intake in adults

Cellular energy metabolism depends on two main energy substrates: glucose a nd fatty acids. The major determinants of the fuel mix oxidized are glucose availability and insulin secretion that both promote glucose oxidation. Fa tty acid oxidation occurs mainly when glucose availability is reduced, for instance during the postabsorptive period, or when energy expenditure is in creased, for instance during exercise of long duration. When eucaloric diet s with high carbohydrate and low fat content are ingested, tie novo lipogen esis is stimulated in adults, bur the rate of conversion of glucose to fatt y acids is low, which means that carbohydrate intake does not have much inf luence on fat requirements. The lower limit of fat intake depends on three factors: the fat requirement to meet energy needs, the need for essential f atty acids, and the amount of fat in the diet that is necessary to absorb f at-soluble vitamins. The lower limit of fat intake to meet the energy needs of adults is assumed to be between 10 and 15% of dietary energy, provided that enough carbohydrates are available. For adults, the requirement for es sential fatty acids is in the range of 3-5% of dietary energy for linoleic acid, and 0.5-1.0% of dietary energy for linolenic acid. Fat energy should not be below 10% of total energy intake in order to ensure an unrestricted absorption of far-soluble vitamins, particularly vitamins A and E. The reco mmendations on upper limits of fat intake for adults must take into account the degree of physical activity. International recommendations indicate th at active individuals in energy balance may consume up to 35% of their tota l energy intake as dietary fat, whereas sedentary individuals should not co nsume more than 30% of their energy from fat. Saturated fatty acids should not exceed 10% of the energy intake.