Weight loss

Published on 09/04/2015 by admin

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Last modified 09/04/2015

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Chapter 24 WEIGHT LOSS

KEY POINTS

• Weight loss is defined as >5% loss of usual body weight over a period of 6–12 months.
• Body mass index (BMI) is defined as body weight in kg divided by height in metres squared (kg/m2).
• Weight loss in elderly people is largely caused by a reduction in food intake and contributes to morbidity and mortality.
• Potential causes of weight loss are strongly influenced by the age at presentation.
• A cause for weight loss can be established in at least 75% of patients.
• Management is determined by the cause. Depression is the most common treatable cause.

INTRODUCTION

The major influences on body weight are caloric intake, intestinal absorption and utilisation. The purpose of this chapter is to outline an approach to the diagnosis and management of weight loss, particularly in adults.

An important message is the need for greater attention to undernutrition as a cause of weight loss. In the elderly, weight loss is strongly associated with functional decline and mortality.

Definitions

In research studies, weight loss may be defined as a weight loss of >5% of usual body weight over a period of 6–12 months. Weight loss >10% is usually associated with protein–energy malnutrition while weight loss >20% implies severe protein–energy malnutrition and significant organ dysfunction. One quantitative measure of nutritional status is that of body mass index (BMI). This is defined as body weight in kg divided by height in metres squared (kg/m2). A BMI lower than 17 is consistent with undernutrition. Other anthropometric measures include arm circumference and triceps skin fold thickness, but these are affected, at least to some extent, by skin changes associated with ageing.

Prevalence

Features of undernutrition or significant weight loss have been documented in at least 10% of elderly patients attending outpatient clinics, 25% of elderly inpatients needing acute care and 40% of patients in nursing homes and other institutions.

PATHOPHYSIOLOGY

The weight loss that occurs with ageing is largely caused by a reduction in food intake. This has been attributed to a variety of factors including age-related losses in taste and smell, age-related decreases in opioid receptors and enhanced sensitivity to the satiating effects of cholecystokinin. Other factors may include changes in the secretion of leptin and sex hormones and age-related changes in intestinal absorption, sometimes mediated by changes in gastrointestinal motility. In the setting of acute and chronic disease, anorexia and weight loss can be caused by a variety of factors including ill health, weakness and side effects from medication. Some of these effects may be mediated by elevated levels of cytokines such as interleukins and tumour necrosis factor and by elevated levels of corticotrophin-releasing factor. At a practical level, at least 20% of inpatients in acute hospitals have a nutrient intake of <50% of their calculated maintenance energy requirements.

CAUSES OF WEIGHT LOSS

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