Aging and appetite : social and physiological approaches in the elderly

Aging is often accompanied by anorexia of aging, described as a decline in appetite, a lower dietary intake and followed by unexplained weight loss. The present thesis described research on anorexia of aging. Focus was given to social and physiological determinants of appetite and the relationship with dietary intake and/or body weight was examined in observation (chapter 2) as well as in intervention studies (chapter 3-6).First a cross-sectional observation study (Chapter 2) on taste, smell appetite and hunger feelings in elderly subjects was conducted. The aim was to detect possible differences in appetite between different health categories of elderly using the Appetite, Hunger feelings and Sensory Perception (AHSP) questionnaire. Three health categories of elderly subjects were selected for this study: free-living with no help, free-living with help and nursing home elderly. For each group, collected data were general characteristics, anthropometry and answers to the AHSP. The AHSP questionnaire includes 29-items focusing on feelings of hunger and appetite as well as taste and smell perception addressing both the present situation and the period before retirement. Results indicated a decrease in feelings of appetite and hunger with a deterioration of health conditions. It also shows that in relatively healthy elderly subjects appetite remained an indicator of t)ody weight while this relation disappeared in nursing home elderly residents.The decline in average food intake in elderly people is attributed to both physiological and social factors. These factors are usually studied in isolation. The study described in Chapter 3 concerned an experiment in which the effect of social setting on food intake was compared with the effect of physiological challenges on food intake in 24 elderly subjects. Physiological effects were assessed using a preload-test-meal design with a no load, and 4 preload conditions. The preloads consisted of 300g of strawberry yogurt drink. The test-meal, served 90 minutes after the preload consumption, was a lunch of which subjects could eat ad libitum. During the lunch consumption subjects were either in a very cozy environment eating with 6 to 8 people on one table or in a non-cozy environment with a delimited space and only one person per table.Results showed that the presence of others did only promote longer meal duration but there was no increase in dietary intake. In apparently healthy elderly subjects, physiological parameters have a stronger effect than changes in social environment on appetite and energy intake. However, meal duration, an intermediate factor of social facilitation, was strongly affected by meal environment in this elderly population.In Chapfer 4, long-term effects of a changed environment and atmosphere of meal consumption on appetite and health were explored during a one-year intervention study in a nursing home (n=38). An effort was made to improve the quality of the mealtime experience of subjects in the experimental group by changes on the attractiveness of the dining room, the food service, and the organization of the mealtime assistance. For control subjects, mealtime experience was unchanged from the situation before the onset of the study. Both groups were served the same meals and meal patterns were also the same for the two groups. Dietary intake, indicators of nutritional and health status and quality of life (Sickness Impact Profile and Philadelphia Geriatric Center Moral Scale) were assessed before and after one year of intervention. Body weight information was obtained every four months. Increased body weight, stable biochemical indicators of health status and quality of life scores in the experimental group indicated a relatively stable health condition while negative changes in the control group suggested a decline in health status. These results suggest that relatively minor changes in mealtime circumstances of elderly nursing home residents can have beneficial effects on their food intake and nutritional status. In other words, social support and physical environment could be reported as one of the determinants for dietary intake in elderly nursing home residents. Further these changes were simple to implement ands could be made without additional cost to the nursing home.In chapter 5 we investigated the effects of the introduction of an evening vitamin- and energy-rich snack on average dietary intake and body weight of nursing-home elderly. A parallel intervention study design was used. Every evening for 30 days, the experimental group (n=26) consumed an energy and vitamin-rich drink (200 ml; 1,2 MJ) around 7:30 p.m. whereas the control group (n=26) received usual coffee and tea.A regular intake of an evening energy and vitamin-rich drink in the evening had a positive influence on dietary intake and led to an increase in body weight, thereby helping in the prevention of weight loss in nursing-home elderly.Taste and smell losses occur with aging. These changes are supposed to decrease the enjoyment of food, subsequently reduce food consumption and negatively influence the nutritional status of elderly, especially the frail ones. Flavor amplified foods have been proposed to be a feasible way to compensate the age-related decreases. In chapter 6, we determined if the addition of flavor enhancers to the cooked meal for nursing home elderly promotes food consumption and provides nutritional benefits. During 16 weeks, the cooked meal of the intervention group (n=36) was sprinkled with flavor enhancers, while the control group (n=31) received the regular cooked meal. Feelings of appetite, dietary intake and anthropometry were assessed before and at the end the intervention.Intake at the cooked meal, hunger feelings and body weight increased in the intervention group but not in the control group. Since the repeated intake of flavor amplified foods did not lead to boredom, it suggests that the intervention was well accepted. Adding ready to use flavor enhancers to the cooked meal was in the present study a simple but effective way to improve daily feelings of hunger, actual dietary intake and body weight in a nursing home population with a steady health status.Finally in chapter 7, the main findings of the studies described in this thesis are discussed in relation to the findings of other. First, appetite and the extent to which food is enjoyed varied greatly between people. In the elderly, these differences may be explained by differences in the health characteristics of the groups studied. Second, social and environmental factors remained important determinants of appetite, more especially in elderly with an unstable or poor health condition. Third, the incapacity to adjust energy intake in the elderly on both short and long-term seems to be a non-reversible process. In daily practice, this lack of regulation suggests that the consumption of energy and nutrient dense supplements between meal could help to prevent weight loss in older adults.The properties of foods and the context in which the foods are consumed remain important determinants of dietary intake in the elderly and are thereby major risk factors for anorexia of aging and its subsequent weight loss. From a public health perspective, the lack of regulation in appetite and dietary intake should encourage the use and consumption of nutritional interventions in elderly at risk.