Traditionally, public health interventions targeting obesity have focused on weight or body mass index (BMI - weight in kg/height in m²). As a result, the general public tends to synonymously associate weight with obesity. It is only recently that abdominal girth or the waist to hip circumference ratio has been used to define obesity reflecting the visceral and abdominal accumulation of fat in obese individuals. Recent studies have also reported a protective effect of overweight BMI (i.e. 25-30 kg/m²) in older people.1 Weight loss is not confined to fat loss only given that fat, muscle, bone and water contribute to weight. With weight loss, there is also muscle mass loss. Therefore, public health messages should emphasize the importance of preserving muscle mass and strength when discussing obesity and recommending weight loss.

Nutritional frailty is common in older people and is defined as the disability that occurs in old age due to rapid, unintentional loss of body weight, muscle mass and muscle quality.2 The anorexia of ageing describes the reduction in energy intake seen with increasing age. This reduction in energy intake often exceeds the reduction in energy expenditure resulting in weight loss.3 Changes to both muscle mass and muscle quality affect muscle strength and the lack of muscle mass and quality is referred to as sarcopenia.2 Reduced muscle strength and reduced nutritional intake are associated with frailty,4 which results in functional decline, social isolation, falls, increased risk of hospitalisation and an increased mortality risk.5 It follows that interventions that prevent nutritional frailty may maximise the length of time people spend being healthy and independent.

Older people have impaired homeostasis when it comes to weight regulation. Following unintentional weight loss, for example after an acute illness, intervention will be required to ensure that the lost weight (and muscle mass) is regained. In one study, Roberts et al. underfed young and old men by 3.17 MJ/day (750 kcal/day) for 21 days and weight loss was reported in both groups.6 After the underfeeding period both groups of men were allowed to eat as much as they wanted. Young men ate more than they did before the underfeeding period and returned to their previous weight. The older men did not increase their caloric intake and so, did not regain the weight they had lost.

With weight change the proportion attributable to change in muscle mass as opposed to fat mass is greater with weight loss than weight gain. Therefore, weight loss is associated with muscle mass loss. In the Health ABC Study, 2163 older (mean age 73 years) participants with >3% change in body weight were observed over a period of 4 years.6 Older participants who lost weight lost 5-6% of their initial lean (muscle) mass and 11-13% of their initial fat mass, while those with weight increases gained only 2-3% of their initial lean mass and 14-18% of their initial fat mass. Therefore, ideally weight loss or muscle loss should be avoided altogether.

One should also not be complacent when weight is stable as muscle mass and strength can still decrease. Goodpaster et al. in their study of 1880 subjects aged 70-79 years (Health ABC Study) reported a loss of muscle mass and strength over 3 years despite no significant change in weight and BMI.7 Muscle strength loss exceeded muscle mass loss suggesting that muscle quality loss had occurred.

Contrary to common belief that older people require less nutrients because they do less, it has been reported that older people should increase their daily protein intake to 1-1.2 g/kg per day.8 Increased protein intake alone without exercise is practically pointless. Exercise (especially resistance) and nutritional supplementation (especially protein) are necessary in combating frailty and preserving muscle bulk and strength.9

With the ageing of the population, there is a need to focus on preventative strategies that maintain muscle bulk and strength in order to maximise independence by reducing the adverse health effects of nutritional frailty. Acute hospitalisation of older patients often leads to bed rest or immobility. The effects of immobility in healthy older people have been shown to be associated with loss of skeletal muscle mass especially in the lower extremities, decreased strength and decreased protein synthesis.10 This is often further exacerbated by reduced caloric and protein intake. Pennington and colleagues had reported, as far back as 15 years ago, that undernutrition is underrecognised in the acute-care setting and that weight is lost while patients are in hospital.11 Sadly, it is unlikely that this situation has changed.12

Current models of care are possibly not effective in the management of frail, older patients as it has been reported that up to 12% of patients age 70 years and older experience a decline in the activities of daily living function following admission to acute care.13 The risk of experiencing functional decline following acute care is higher in the oldest old (85+). The fastest growing cohort in acute care are aged 85 years and above. Interventions that have traditionally been provided in rehabilitation or long-term care settings targeting nutritional and physical health may be effective in acute care and contribute towards the preservation of muscle function. In the last issue of this journal, Gordge and colleagues discussed their experience with the implementation of communal dining in an acute care ward.14 This simple strategy is likely to exert benefit through: increased nutritional intake, increased socialisation, improved mood, increased physical activity, normalisation of function and improved supervision. Walking to and from the dining room encourages physical activity and co-location of patients in one area for a period of time would allow for the interdisciplinary team assessment and development of collaborative management plans.

Nutritional frailty is common in the community and is associated with significant morbidity. There is a need to revisit models of care and perhaps lessons learnt from various settings may be applicable across the continuum of care. Exercise and adequate protein intake are fundamental towards ensuring the preservation of muscle function and ensuring maintained independence. Public health campaigns must emphasize this.

¹Associate Professor, Department of Medicine, Discipline of Medicine, Faculty of Health Sciences, University of Adelaide, and

²Aged and Extended Care Service, The Queen Elizabeth Hospital, Central Northern Adelaide Health Service, Adelaide, South Australia, Australia

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