In general, aging causes a loss of bone and muscle and an increase in body fat due in part to hormonal changes that regulate metabolism. For instance, a decrease in growth hormone and
androgens contributes to the loss of lean body mass and insulin resistance reduces the ability to use protein. Prolactin, a hormone that helps maintain body fat, increases with age. These changes in body composition are one of the reasons why calorie needs decrease with aging.

Progressive loss of muscle mass is a common feature of aging (Paddon-Jones et al., 2015). Physiologic and behavioral changes account for the 1% to 2% annual loss of muscle mass that begins around the age of 50 years. Because the reserve of muscle mass is large, function is not impaired. In the early 60s, a person’s loss of muscle becomes evident as muscle strength declines an average of 3% per year. An estimated 20% to 40% of muscle strength may be lost by the time a person reaches the 70s. Acute or chronic illness and inactivity—alone or in combination with malnutrition or inadequate protein intake—hastens the loss of lean body mass and functionality (English & Paddon-Jones, 2010).

Sarcopenia occurs when age-related loss of skeletal muscle mass is accompanied by loss of muscle strength and function; it is a main determinant of disability and mortality (Manini & Clark, 2012). Advanced sarcopenia is characterized by physical frailty, increased likelihood of falls, impaired ability to perform activities of daily living, and diminished quality of life (Paddon-Jones, Short, Campbell, Volpi, & Wolfe, 2008). Sarcopenia is estimated to affect 8% to 40% of adults over the age of 60 years and approximately 50% of those over the age of 75 years (Berger & Doherty, 2010). Sarcopenia should be considered in all older adults with observed declines in physical function, strength, or overall health and especially in older adults who are bedridden, who cannot rise independently from a chair, or who have a slow gait (Evans, 2010).

Sarcopenia the loss of skeletal muscle mass, strength, and function that occurs with aging.

Older adults exhibit less hunger and earlier satiety than younger adults (Bernstein & Munoz, 2012). Among the possible causes of diminished appetite are a decrease in physical activity, decrease in metabolic rate, a decrease in gastrointestinal (GI) hormone secretions, delayed gastric emptying, social isolation, cognitive impairments, medication side effects, and impaired chewing or swallowing. Diminished appetite contributes to undernutrition in both community and institutional settings and can lead to unintentional weight loss, which is often associated with poor health outcomes and is a marker for deteriorating well-being in older adults (Bernstein & Munoz, 2012).

A decrease in muscle mass and strength can lead to a progressive decline in physical function. Among community-resident Medicare beneficiaries 65 years and older in 2013, 33% had difficulty performing one or more activities of daily living (ADLs) and an additional 12% reported difficulty with one or more instrumental activities of daily living (IADLs) (USDHHS, AOA, 2014). Functional limitations may impair the ability to eat or prepare or shop for food. Chronic diseases that increase the risk of functional limitations include cerebrovascular accident, diabetes, ischemic heart disease, and arthritis (Bernstein & Munoz, 2012).

Activities of Daily Living (ADLs) bathing, dressing, eating, and getting around the house, and using the toilet.

Instrumental Activities of Daily Living (IADLs) using the telephone, doing housework, preparing meals, shopping, managing money, and taking medication.

Loss of a spouse, difficulty ambulating, and sensory impairments such as loss of vision or hearing are factors that contribute to social isolation. Eating alone is a risk factor for poor nutritional status among older adults, especially among men. Food choices are not necessarily poor; rather, it is the quantity of food consumed that is often inadequate.

Depression is not a normal consequence of aging but occurs in many older adults. As many as 5% of community-dwelling older adults meet the diagnostic criteria for major depression and up to 15% have clinically significant symptoms of depression that interfere with functioning (Hybels & Blazer, 2003). The prevalence of depression is even higher among older adults with medical illnesses. Weight loss or gain is among the many symptoms of depression.

A study of community-dwelling older adults found that 51% reported using five or more medications daily (Heuberger & Caudell, 2011). Medications can cause side effects that interfere with intake, such as changes in taste and smell, dry mouth, early satiety, anorexia, and GI upset. Polypharmacy in older adults is associated with a decrease in walking speed, disability, mortality, cognitive decline, and delirium (Husson et al., 2014). Nutritionally, an inverse relationship has been observed between the number of medications used and the intakes of fiber, fat-soluble vitamins, B vitamins, and minerals; a positive relationship was noted for the intake of cholesterol, carbohydrate, and sodium (Heuberger & Caudell, 2011).

Older adults are urged to follow the adult guidelines for physical activity or as their abilities allow (Box 13.2). Strong evidence shows that for adults and older adults, physical activity lowers the risk of heart disease, stroke, type 2 diabetes, hypertension, dyslipidemia, metabolic syndrome,
and weight gain in addition to improving cardiovascular and muscular fitness, preventing falls, reducing depression, and improving cognitive function (USDHHS, 2008).

Healthy eating can enhance wellness, improve nutritional status, reduce the risk of chronic disease, help manage chronic disease, and help maintain energy levels. Although a lifetime of healthy eating is optimal, adopting a healthy eating pattern even in later life has health benefits. A study among women who began a Mediterranean-style eating pattern in their 50s and 60s found they had a 40% greater chance of living beyond 70 years with greater health and well-being (Samieri et al., 2013).

Calorie recommendations decrease with aging related to the typical decrease in physical activity and the changes in body composition that lower metabolic rate (Fig. 13.2). As with other age groups, individual variations in activity exist. Compared to younger adults, older adults need fewer calories yet generally have the same or higher requirements for vitamins and minerals, making the concept of nutrient density even more important.

The Recommended Dietary Allowance (RDA) for protein remains constant at 0.8 g/kg for both sedentary and physically active men and women from the age of 19 years on (Institute of Medicine, 2005a). This level represents the minimum protein intake necessary to avoid progressive loss of lean body mass as determined by nitrogen balance studies (Wolfe, Miller, & Miller, 2008). However, the data were gathered almost entirely in college-aged men who can maintain nitrogen balance on less protein than can older adults (Wolfe et al., 2008). This one-size-fits-all protein recommendation does not consider age-related changes in metabolism, immunity, hormone levels, or progressing frailty (Bauer et al., 2013).

Lean Body Mass all body components except stored fat; the fat-free mass of the body.

A protein intake greater than the RDA has been shown to improve muscle mass, strength, and function in older adults and may also improve immune status, wound healing, blood pressure, and bone health (Wolfe et al., 2008). One reason why older adults need more protein than younger adults is that they have a declining anabolic response to protein intake; that is, their threshold for the amount of protein needed to stimulate protein synthesis is higher. Protein need may be higher in response to the inflammatory and catabolic impact of chronic and acute diseases that commonly occur with aging (Walrand, Guillet, Salles, Cano, & Boirie, 2011). Paradoxically, although older adults

need more protein, their intake is less than that of younger adults. Approximately one-third of adults over the age of 50 years do not even meet the RDA for protein (Houston et al., 2008). Factors that may contribute to a decrease in protein intake include the cost of high-protein foods, the decreased ability to chew meats, lower overall calorie intake, and changes in digestion and gastric emptying.

The PROT-AGE Study Group, composed of an international panel of experts, met for the first time in 2012 for the purpose of developing updated evidence-based recommendations for optimal protein intake for older adults (Bauer et al., 2013). A summary of PROT-AGE recommendations is listed in Box 13.4. In addition to consuming more total protein, it is recommended that protein be evenly distributed throughout the day (e.g., 25-30 g protein per meal, the equivalent of 3-4 oz protein foods) to maximally stimulate muscle protein synthesis and thus slow or prevent the progression of sarcopenia in older adults (Paddon-Jones et al., 2015). Animal protein, but not vegetable protein, may be associated with less lean mass loss. Higher amounts of leucine, an essential amino acid that stimulates the majority of protein synthesis, are recommended (Bauer et al., 2013). Researchers are also considering whether increasing protein intake earlier in life, such as during middle-age, will promote long-term muscle health. More research is needed to determine protein and leucine thresholds, what causes anabolic resistance to low protein intakes in older adults, and who best benefits from protein interventions to prevent or manage sarcopenia (Rodriguez, 2015).