26 Chronic diseases and Body composition

Kshetrimayum Surmala and Meenal Dhall

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Contents:

 

1.  Introduction

2.  Levels of body composition

3.1 Chronic diseases

3.1.1. Risk factors for chronic diseases

3.2 Association of Human body composition with chronic diseases

3.2.1. Obesity and Body Composition

3.2.1.1. Obesity and body composition

3.2.2. Diabetes Mellitus and Body Composition

3.2.2.1. Diabetes and Body Composition

3.2.3. Thyroid diseases and Body Composition

3.2.3.1. Thyroid diseases and Body Composition

3.2.4. Body composition and cardiopulmonary diseases

3.2.4.1. Body composition and Coronary Artery Disease (CAD)

3.2.4.2. Body Composition and Chronic Obstructive Pulmonary Diseases (COPD)

3.  2.5. Body Composition and Cancer

3.2.5.1 Breast Cancer

 

Learning Objectives:

  • To understand the concept of body composition, different levels of human body composition and its assessment.
  • To understand the concept of chronic diseases and risk factors associated with body composition.
  • To understand the association of body composition with chronic diseases.

    Introduction

 

The term body composition is defined as “the make-up of the body in terms of the absolute and relative amount of skeletal mass, muscle mass, adipose tissue, internal organs and other tissues” (Bogin, 1999). Measuring body composition is significant for assessing a person’s health status and it can be helpful for establishing optimal weight for health and physical performance. Fat-free mass (FFM) and fat mass (FM) have many medical implications and are helpful tools to evaluate the nutritional status. However, other components of body composition also influence health outcomes and there are growing evidences which links body composition with health risk together.

 

Excess body weight may lead to certain level of obesity and increased risk of variety of chronic diseases while deficiency in energy stores due to inadequate body fat is associated with morbidity and mortality (James et al., 1988). Ideal body composition is one of the components of fitness and it is being used increasingly in the assessment of growth and nutritional status, fitness, work capacity, disease and its treatment (Norgan, 1995).

 

Levels of body composition

 

There are considerable changes in the chemical composition of the human body throughout the life cycle. The chemical components of the body which represents the absolute and relative proportions of water, minerals, protein and lipids are influenced by growth, maturation and ageing. The five – level model in body composition which is known as the central model considers the body mass as a sum total of all the components at each of the five levels namely, atomic (e.g., carbon, oxygen and hydrogen), molecular (water, lipid, protein), cellular (extracellular fluids), tissue-organ (adipose tissues, bone, skeletal muscles, visceral organs) and whole body (head, trunk, appendages) (Wang et al., 1992).

 

The specific components of five levels are described in figure 1.

 

Figure 1: Five level model of body composition

 

Source Link: www.nzdi.org

 

At the atomic level, the body mass consists of four elements: oxygen, carbon, hydrogen and nitrogen. Other elements such as potassium, calcium, sodium, chlorine and magnesium are also accounted. Molecular compartments consist of water, lipid, protein, glycogen, bone minerals and soft tissues minerals. Thus, the body weight is viewed as: body weight= water + protein + mineral + fat. Various other models can be created from molecular level ranging from the two compartment models to six compartment models.

 

The two compartment models consist of FM (fat mass) and FFM (fat free mass). Fat free mass refers to the body weight minus the ether-extractable fats while the fat mass includes the storage and essential lipids. Fat and lipids are often used interchangeably used, but in body composition research, fats refers to the specific family of lipids i.e. triglycerides whereas lipids refers for ether and chloroform extractable lipids such as triglycerides, phospholipids etc.

 

The cellular level of body composition consists of extracellular solid, extracellular fluid and cells. The cell can be additionally partitioned into two components: body cell mass (BCM), the metabolically active component and fat.

 

The tissue – organ level of body composition consists of the adipose tissue, organs, skeletal muscles, visceral organs and bones. Adipose tissue consists of adipocytes with collagenous, elastic fibers, fibroblast and blood vessels. Single solid organs such a brain, liver, spleen and heart are some other organ level components.

 

Whole- body level of body composition consists of regions like appendages, trunk and head which are usually described by anthropometric measures such as length, circumferences and skin folds. Body mass index (BMI) and skin fold thickness are considered as the most common anthropometric indicators of body composition. The five level models clearly manifest the relationship between the major body components and the basics structure of human body.

 

There are various models for partitioning the body mass into meaningful compartments. The most commonly used methods for assessing body composition are two compartments model which includes fat and fat-free mass, expressed as body weight = fat free mass + fat mass and three compartments model consisting of fat mass (FM), partitions fat free mass into fat free dry mass (FFDM) and total body water (TBW), expressed as body water = TBW + FFDM +FM. Models which include three or more components are referred to as multicomponent models.

 

Body composition, in general is defined as the relative portion of fat free mass and fat mass. Body fat includes essential and energy stores or storage body fat. Essential body fats are found in the nerve tissues, cell membrane, bone marrow and organs. Energy stores or storage fats represents the energy stores which accumulates and decreases with respect to nutritional and physiological condition (Poskitt, 1995). Total body fat is percentage for young men is estimated to between 12% to 15% and for young women is between 25% to 28%.

 

There are two principle methods for assessing body composition namely, direct measurement by chemical analysis of the animal body or human body and indirect estimation by hydrostatic weighing, simple anthropometric measurements, and other clinical and laboratory procedures.

 

The common methods include anthropometry (especially skinfold thickness), bioelectrical Impedance or total body electrical conductivity, computed tomography, X-rays, air plethysmography, ultrasound, water displacement methods, computed axial tomography (CAT), magnetic resonance imaging (MRI), neutron activation analysis, isotope dilution etc.

 

Chronic diseases

 

Chronic disease refers to a medical condition or disease which persists for a long time. It is of multi-factorial etiology which has their origins at young age and takes decades to become fully established. Chronic non- infectious diseases include type 2 diabetes, heart disease, stroke, hypertension, dental disease, cancer, chronic respiratory diseases and osteoporosis. Chronic diseases also known as non communicable diseases (NCDs) are now a major global burden in public health. By 2020, the burden of NCDs is expected to increase to 57% and it has been projected that in developing countries, 71% of deaths due to ischaemic heart disease (IHD), 70% of deaths due to diabetes and 75% of deaths due to stroke will occur.

 

Risk factors for chronic diseases

 

The burden of chronic diseases or non communicable diseases (NCDs) are greatly influenced by societal factors such as socioeconomic status, education, employment, and environmental factors that influence behavior and lifestyle, leading to the development of chronic diseases. With the economic development, rapid urbanization, food security and increased health care services in developing countries there has been decline in under nutrition-related diseases. However, these factors on the other hand have exacerbated the development of chronic diseases, due to unhealthy diets, sedentary lifestyles and lack of physical activity. Chronic diseases are now a major global burden in public health.

 

The role of environment as determinants of chronic diseases is well established. Environmental factors in association with social factors such as socio-economic status form a chain of events that that influence the behavior, leading to the development of biological risk factors that cause the chronic diseases. Modifiable risk factors such as unhealthy diet, physical inactivity and tobacco use triggers the development of chronic diseases. Altogether, these may serve as an intermediate risk factors of raised blood pressure, abnormal blood lipids, raised glucose level, overweight and obesity. Harmful alcohol use is also a major contributing factor.

 

Chronic diseases are a complicated disease entity and are interconnected in various circles with other diseases in the sense that they become risk factors themselves. For example, there is strong association of overweight and obesity with, hyperlipidemia, insulin resistance and insulin resistance. All these risk factors contribute to the development of diabetes and cardiovascular disease. Thus, these results in clustering of risk factors, the so called metabolic syndrome which includes dyslipemia, hyperglycemia and hypertension, mediated by insulin resistance and the end can result in the development of type 2 diabetes.

 

Table 1: Risk factors for chronic diseases and non-communicable diseases

 

Source Link: www.who.int/chp

 

Association of Human body composition with chronic diseases

 

Body composition has a wide range of health consequences and influence susceptibility to diseases. Distribution of the total and relative amount of fat represents an independent risk factor for certain diseases. It is important to understand how changes in body composition relate specifically to risk for chronic disease morbidity and mortality. There is a strong association of android distribution fat (fat on the upper trunk of the body) with hypertension, non-insulin-dependent diabetes and gallbladder disease and is more typical of men. The gynoid distribution (the tendency to accumulate fat on the hips, thighs, and arms) are more common in women.

 

The most common disorders related to abnormal body composition is obesity, defined by excessive accumulation of body fat resulting in adverse effect on health. This can lead to abnormalities in carbohydrate metabolism, lipid high blood pressure and a major risk factor for development of non insulin dependent diabetes. However, there are several diseases associated with abnormal distributions of body water across the intracellular and extracellular spaces due to inadequate storage of fats and proteins in the body.

 

Body Composition and Metabolic Diseases

 

One of the major interests in the body composition research is the health implications of excess fat or abnormal distribution of fat and has been declared as an epidemic in developed countries (WHO/FAO, 2003). In both developing and developed countries, due to nutritional transition, unhealthy dietary and lifestyle pattern chronic or non communicable diseases have become principal global causes of morbidity and mortality. India, at present faces a combination of chronic diseases and communicable diseases where the burden of chronic diseases exceeds that of communicable diseases.

 

Metabolic diseases such as type 2 diabetes, hypertension, hyperthyroidism and obesity are strongly associated with the weight loss or gain or alteration of body composition by directly affecting the metabolism of carbohydrate, fat, lipid and proteins. Major health implication or disorders due to abnormal body composition are discussed below.

 

Obesity and Body Composition

 

Obesity is an excessive accumulation of body fat resulting in adverse effect on health associated with chronic diseases. Obesity is defined in epidemiological research as a BMI (Body Mass Index) of 30 kg/m2.Though obesity can be determined by many other methods, calculation of BMI defined as weight (in kg) divided by height (in meters square), is widely used to classify underweight, overweight and obesity in adults. However, a given BMI may not correspond to specific population as body fat distribution varies accordingly to body build and proportions. There is a higher risk of developing chronic diseases with individual having excess abdominal fat and have tendency to deposit excess subcutaneous and visceral fat in the abdominal region as compare to individuals with excess fat in the lower body.

 

The fundamental cause of obesity is excessive consumption of high calorie foods with less physical activity level i.e. when the energy intake is in excess of expenditure. Obesity has multi-factorial epidemiology such as genetic, environmental, psychological, age, sex and socio-economic factors. However, about 25% to 40% of the variability in body fatness can be attributed to genetic factors (Bouchard, 1994).

 

Influence of obesity on body composition

 

Increased body weight is the most fundamental change in body composition associated with obesity. BMI is an accurate surrogate marker for adiposity with individuals who are obese (Jackson et al. 2002). However, obesity not only involves an increase of body weight but may also affect density of FFB (fat free body) and distributions of body water across the intracellular and extracellular spaces. In some individuals who are obese, triglycerides present in the adipose tissue may increase in addition to water (Deurenberg et al., 1989). Although, there is a high variability among individuals, researchers have noted the level of hydration to be higher in obese men and women (74.2-77% FFB) as compared to leaner individuals ‘72-74% FFB’ (Abu et al. 1989). Obesity is also known to affect the metabolism of protein and minerals. In obese men and women, the relative amount of minerals (7.2-8.1%) and proteins (20-21%) are higher than the assumed values ‘6.8% and 19.4 %’ (Fogelholm et al., 1997).

 

Diabetes Mellitus and Body Composition

 

There are two clinical types of diabetes mellitus, namely type 1 and type 2. Type 1 also known as insulin- dependent diabetes mellitus is characterized by high blood glucose level (hyperglycemia) which is caused by a lack of insulin production due to auto-immune destruction of beta cells of pancreases. Type 2 diabetes often referred to as non insulin dependent diabetes mellitus, is characterized by insulin resistance where the body is unable to utilize the glucose derived from carbohydrates food or glycogen store in the tissues.

 

Diagnosis of type 2 diabetes usually occurs on the onset of middle adulthood and is associated with obesity which leads to elevated blood sugar and itself can lead to insulin resistance. There is increasing reports of children with type 2 diabetes and have become serious health issues. It has been estimated in the adult population that the prevalence of diabetes mellitus will raise from 4% in 1995 to 5.4% in 2025. Obesity is a major risk factor for development of non insulin dependent diabetes. In the past 2 decades, epidemiological research has been examining the association between adipose tissues and insulin resistance.

 

Abnormal fat distribution and certain patterns of adipose tissues have found to be associated with the so called metabolic syndrome characterized by raised blood pressure, insulin resistance, abnormal blood lipids, raised fasting glucose level, overweight and obesity. Insulin resistance is a principal mechanism by which obesity is considered to heighten risk of type 2 diabetes.

 

Measurement of waist circumference also helps in assessing the aspects of fat distribution and also the risk of developing diseases like diabetes mellitus. WHO has classified cutoff values of waist circumference according to which a waist circumference of greater than 102 cm in men and 88 cm in women is a risk factor for type 2 diabetes, cardio-vascular diseases and hypertension. However, these values were revised for Asian Indian population as 90 cm in men and 80 cm in women. Measurement of visceral adipose tissue helps in understanding the type 2 diabetes and insulin resistance.

 

Assessment of subdivisions of abdominal adiposity and subcutaneous abdominal adiposity were enabled through magnetic resonance imaging (MRI) and computed tomography (CT). Visceral adipose tissue has been found to be associated with insulin resistance , increased risk for hypertension, glucose intolerance and dyslipidemia. Strong association has found between visceral adipose tissue and insulin resistance in individuals without type 2 diabetes also. Individuals who are overweight and obese have an elevated content of fat within the liver. It has been reported that the prevalence of fatty liver may be 75% or greater in those with a BMI above 30 kg/m2 and type 2 diabetes (Chitturi and Farrel, 2001).

 

Influence of diabetes on Body Composition

 

Earlier, Type 1 diabetes was commonly thought to be a catabolic disease, producing loss of protein and FFM (Fat Free Mass). The FFM of individuals with type 1 diabetes was normal at the onset of the disease, even though the body weight (BW) was 6.5 kg below ideal weight and FM was 25% lower than that of the healthy individuals (Rosenfalck et al., 2002). Researchers have concluded that uncontrolled type 1 diabetes produces a fat, rather than a protein, catabolic state. Individuals with type 1 diabetes tend to have a less value of total body fat, abdominal fat and % BF as compared to healthy controls and type 2 diabetic patients (Gomez et al. 2001). During the first year of insulin therapy of type 1 diabetic patient, average BW increases to 4.3 kg, with a 13% increase in FM and a 5% increase in FFM. Patients with type 1 diabetes have a lower bone mineral density compared to healthy individuals (Munoz-Torres et al., 1996).

 

Thyroid diseases and Body Composition

 

Thyroid stimulating hormone generally controls the metabolic function including metabolism of fat, protein, carbohydrate and minerals. Hyperthyroidism is characterized by increased secretion of thyroid hormone and Grave’s disease which is the most common cause of auto-immune disease (Beers & Berkow, 1999). Whereas hypothyroidism is caused due to deficiency of thyroid hormone resulting from auto-immune thyroiditis (i.e., inflammation of the thyroid gland) and this disease is often associated with a firm goiter.

 

Influence of Thyroid diseases on Body Composition

 

Miyakawa et al. 1999 studied the body composition of patients with thyroid diseases using BIA (bioelectrical Impedance) as compared to age and gender matched healthy individuals. It has been found that patients with hyperthyroidism tend to have less BW, %BF and body cell mass (BCM). It was also found that the reduction in BCM was attributed to a loss of muscle mass. Also, loss of significant bone minerals is also a consequence of hyperthyroidism (Cohn et al., 1973). However, when the BCM of patients with hypothyroidism when compared with healthy controls, it was found to be almost similar even though these patients were fatter and weighed more than the healthy individuals.

 

Body composition and cardiopulmonary diseases

 

Individuals with coronary artery disease (CAD) tend to be overweight and obese while individuals with cardiopulmonary diseases such as chronic obstructive pulmonary diseases, and heart failure often lose weight and lean body tissue because of muscle wasting and the depletion of bone mineral. So, body composition assessment is required for monitoring these patients to enable the clinicians to provide adequate nutritional support.

 

Coronary Artery Disease (CAD) and Body Composition

 

Pathological lesion leading to CAD is called atherosclerosis, defined by accumulation of complex carbohydrates and lipids in the blood vessels. This leads to thickening of the arterial vessels of the body in cerebral, abdominal and peripheral circulation and thus interferes with the oxygen supply to the heart muscle (myocardium). Individuals with coronary artery disease (CAD) tend to be overweight or obese and tend to have more body fat on the upper body. Patients with this disease have an altered fluid status due to increased TBW and extracellular fluids (Massari et al., 2001). In addition, with the congestive heart failure, plasma volume increases and fluid started to accumulate in the lungs, abdominal organs and peripheral tissues.

 

Body Composition and Chronic Obstructive Pulmonary Diseases (COPD)

 

Chronic obstructive pulmonary diseases (COPD) are a condition in which the airflow to the lung is obstructed. Emphysema (permanent enlargement of air spaces in lungs) and chronic bronchitis (persistence inflammation of the mucous membrane of the bronchi caused by bacterial infections or lung carcinoma) are the most common respiratory problem often associated in patients with COPD. Individuals with chronic obstructive pulmonary diseases often lose weight and lean body tissue because of muscle wasting. In a study it was reported that half of the patients with either COPD or severe respiratory insufficiency were underweight (BMI ≤ 18.5 kg/m2) but only a few of the patients were overweight (BMI= 27-32 kg/m2). COPD patients had moderate to severe bone mineral loss as compared to healthy, age matched controls (Engelen et al., 1998).

 

Cancer and Body Composition

 

Body composition not only contributes to the understanding of cancer etiology but also enhance the ability to identify the high risk population for prevention and early detection. Cancer remains the second leading cause of death in the United States before 1999. The elevated incidence rates of cancer in these populations are associated with the high prevalence of obesity in developed countries (Calle et al., 2003). Obesity and physical inactivity often coexist and together account for one fourth to one third of worldwide cases of colon, breast, kidney, esophageal and breast cancer (Anonymous 2002 a). Reduced muscle mass and increased bone density are also related to increased cancer risk.

 

Breast Cancer

 

Several studies have been done to understand the relationship between body composition or body size and cancer. As mentioned earlier, the elevated incidence rates of cancer in Western countries may be linked to the high prevalence of obesity (Stoll, 2000). Van Den Brandt and colleagues (2000) in the analysis of seven cohort studies found that for every 4 unit (kg/m2) increment in body mass index or for every 10 kg increase in weight, there was approximately a 10 % to 11% reduction in breast cancer among premenopausal women but a 6 % to 7 % increase in risk for breast cancer among postmenopausal women. This appears that obesity is protective on premenopausal women and appears to be associated with postmenopausal women.

 

Kumar and Colleagues (1995) in a case- control study observed that women who progressively gained weight from puberty to adulthood, especially in the third decade of life have a higher risk for developing breast cancer. Abdominal fat distribution may also contribute to this disease. Framingham study after 28 years of follow-up reported that central subcutaneous fat instead of general adiposity was associated with subsequent breast cancer among women aged 30-62 years. In a study it was found the waist circumference to hip circumference ratio (WHR) was significantly higher in women with cancer as compared to age matched controls. Visceral obesity is also a significant risk factor for breast cancer in women. Insulin resistance and high insulin growth factor (IGF) levels among obese women are other possible links to breast cancer risk.

 

There are many other inflammatory diseases associated with body composition such as rheumatoid arthritis (RA), osteoarthritis, inflammatory bowel disease etc. Rheumatoid arthritis is an autoimmune disease caused due to destruction of joint cartilage and bone. Loss of FFM is a hallmark of RA. Westhovens and colleagues (1997) in a case- control study found that FFM was lower in the arms, legs and trunk of both males and females patients with RA. The association of obesity and osteoarthritis has been demonstrated in many cohort studies and found that both men and women with high BMI have an increased risk of developing osteoarthritis (Zhang et al., 2000).

 

Summary

 

Body composition has a wide range of health consequences and influences susceptibility to diseases. One of the key interests in the body composition research is the health implications of excess fat or abnormal distribution of fat. Distribution of total and relative amount of fat represents an independent risk factor for certain diseases. It is important to understand how changes in body composition relate specifically to risk for chronic disease morbidity and mortality. India, at present faces a combination of chronic diseases and communicable diseases where the burden of chronic diseases exceeds that of communicable diseases. Metabolic diseases such as type 2 diabetes, hypertension, hyperthyroidism and obesity are strongly associated with the weight loss or gain or alteration of body composition by directly affecting the metabolism of carbohydrate, fat, lipid and proteins. There are many health implications or disorders due to abnormal body composition. Increased body weight is the most fundamental change in body composition associated with obesity. Visceral adipose tissue has been found to be associated with insulin resistance, increased risk for hypertension, glucose intolerance and dyslipidemia. Individuals who are overweight and obese have an elevated content of fat within the liver. There are many other inflammatory diseases associated with body composition such as rheumatoid arthritis (RA), osteoarthritis and inflammatory bowel disease. Monitoring and assessing body composition not only contributes to the understanding of etiology of chronic diseases it also enhances the ability to identify the high risk population for prevention and early detection. Measuring body composition is significant for assessing a person’s health status and it can be helpful for establishing optimal weight for health and physical performance.

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     Suggested Readings

  1. Heymsfield, Steven, ed. Human body composition. Vol. 918. Human kinetics, 2005.
  2. Malina, Robert M., and Claude Bouchard. Growth, maturation, and physical activity. Human Kinetics Academic, 1991.
  3. Kenneth J. Ellis & Jerry D. Eastman. Human Body Composition: In Vivo Methods, Models, and Assessment. Springer US, 2013.
  4. McArdle, William D., Frank I. Katch, and Victor L. Katch. Exercise physiology: Nutrition, energy, and human performance. Lippincott Williams & Wilkins, 2010.