For those aged over 75 to 80 years, food intake is often reduced. Broadly speaking, the requirement in total energy consumption drops by 20 to 30% between the ages of 30 years to 80 years. About a third of this reduction is due to the loss of metabolically active cells which drives a reduction in basal metabolism, and about two thirds of this decline is due to decreased physical activity. However, one should be aware that there is considerable variation in energy demand in the elderly, based on body weight, environment and physical activity. Disease processes, too, can affect the need for energy or specific nutrients.
Whilst older people generally have a lower calorific requirement than younger adults, they have the same or even higher need for essential nutrients, partly because the digestive system is less efficient at absorbing these nutrients. The consequence of this is that the diet should be even more nutrient-rich than previously. Reduced food intake particularly affects the intake of proteins and vitamins (15-20% of energy intake should come from protein, 35% from fat and 45-50% from carbohydrates). Therefore, these components of the diet must be given particular consideration, perhaps reducing fat and sugar intake in preference to protein.