CHAPTER ONE

INTRODUCTION

1.1OVERVIEW OF OBESITY

          Obesity is from the Latin obesitas , which means "stout, fat, or plump".   Ēsus is the past participle of edere (to eat), with ob (over) added to it. During the Middle Ages and the renaissance obesity was often seen as a sign of wealth, and was relatively common among the elite Halton and Hu (2004).Obesity has thus historically been viewed as a sign of wealth and prosperity. It was common among high officials in Europe in the Middle Ages and the Renaissance as well as in Ancient East Asian civilizations. In the 17th century, English medical author Tobias Venner is credited with being one of the first to refer to the term as a societal disease in a published English language book (Appel et al,. 2005).

          With the onset of the Industrial Revolution it was realized that the military and economic might of nations were dependent on both the body size and strength of their soldiers and workers. Increasing the average body mass index from what is now considered underweight to what is now the normal range played a significant role in the development of industrialized societies. Height and weight thus both increased through the 19th century in the developed world (Field et al., 2007). During the 20th century, as populations reached their genetic potential for height, weight began increasing much more than height, resulting in obesity. In the 1950s increasing wealth in the developed world decreased child mortality,   but as body weight increased heart and kidney disease became more common. During this time period, insurance companies realized the connection between weight and life expectancy and increased premiums for the obese (Aune et al., 2009)

          Many cultures throughout history have viewed obesity as the result of a character flaw. The obesus or fat character in Ancient Greek comedy was a glutton and figure of mockery. During Christian times the food was viewed as a gateway to the sins of sloth and lust. In modern Western culture, excess weight is often regarded as unattractive, and obesity is commonly associated with various negative stereotypes. People of all ages can face social stigmatization, and may be targeted by bullies or shunned by their peers (Bernstein et al., 2010)

             Obesity is a condition of increased adipose tissue mass as a result of excessive accumulation of fat or triacylglycerol (MFMER, 2015). It can also be described as a complex disorder involving an excessive amount of body fat, this increase in body fat increases the risk of diseases and health problems such as heart disease, diabetes and high blood pressure.  It’s a term used to indicate the high range of weight for an individual of given height that is associated with adverse health effects (CDC, 2010).

Obesity is commonly caused by a combination of excessive food intake, lack of physical activity and genetic susceptibility. A few cases are caused primarily by genes, endocrine disorders, medications or mental disorder.         

A closely related term to obesity is overweight. Overweight as well as obesity are defined as abnormal or excessive fat accumulation that may impair health but this is differentiated through body mass index (BMI).

Body mass index (BMI)

BMI is a simple index of weight-for-height that is commonly used in classifying overweight and obesity in adult populations and individuals. It is defined as the weight in kilograms divided by the square of the height in meters (kg/m2).

BMI provides the most useful population-level measure of overweight and obesity as it is the same for both sexes and for all ages of adults. However, it should be considered as a rough guide because it may not correspond to the same degree of fatness in different individuals.

For adults, BMI values are classified as follows:

Less than 18.5 = underweight

18.5 to 24.9 = normal weight

25.0 to 29.9 = overweight

30.0 or greater = obese

The World Health Organization (WHO) defines "overweight" as a BMI equal to or more than 25, and "obesity" as a BMI equal to or more than 30. These cut-off points provide a benchmark for individual assessment, but there is evidence that risk of chronic disease in population increases progressively from a BMI of 21.

1.2     CAUSES OF OBESITY

1.2.1 ACQUIRED CAUSES OF OBESITY

Fundamentally, obesity is as a result of excessive energy intake compared to energy expenditure. In children, increased energy intake as sugar or fat has been linked to obesity, also decreased physical activity in children (Drewnowski, 2007)

          Also, a slight decrease in energy expenditure in clinical or subclinical hypothyroidism may contribute to weight gain which is usually reversed after thyroid hormone treatment.

Diet

           It’s no secret that the amount of calories people eat and drink has a direct impact on their weight: Consume the same number of calories that the body burns over time, and weight stays stable. Consume more than the body burns, weight goes up. Less, weight goes down.

          There’s ample research on foods and diet patterns that protect against heart disease, stroke, diabetes, and other chronic conditions. Many of the foods that help prevent disease also seem to help with weight control-foods like whole grains, vegetables, fruits, and nuts. And many of the foods that increase disease risk-chief among them, refined grains and sugary drinks-are also factors in weight gain.

          Weight gain in adulthood is often gradual, about a pound a year too slow of a gain for most people to notice, but one that can add up, over time, to a weighty personal and public health problem. There’s increasing evidence that the same healthful food choices and diet patterns that help prevent heart disease, diabetes, and other chronic conditions may also help to prevent weight gain:

Choose minimally processed, whole foods-whole grains, vegetables, fruits, nuts, healthful sources of protein (fish, poultry, beans), and plant oils. Limit sugared beverages, refined grains, potatoes, red and processed meats, and other highly processed foods, such as fast food (Mozaffarin et al., 2011).Though the contribution of any one diet change to weight control may be small, together, the changes could add up to a considerable effect, over time and across the whole society. Since people’s food choices are shaped by their surroundings, it’s imperative for governments to promote policy and environmental changes that make healthy foods more accessible and decrease the availability and marketing of unhealthful foods.

Sedentary lifestyle

           Sedentary lifestyle plays a significant role in obesity. Globally, there has been a large shift towards less physically demanding work, and currently at least 30% of the world's population gets insufficient exercise. This is primarily due to increasing use of mechanized transportation and a greater prevalence of labor-saving technology in the home (Thompson et al., 2011). In children, there appear to be a reduction in levels of physical activity due to less walking and physical education.

           The World Health Organization indicates people worldwide are taking up less active recreational pursuits, while a study from Finland found an increase and a study from the United States found leisure-time physical activity has not changed significantly. A 2011 review of physical activity in children found that it may not be a significant contributor.

In both children and adults, there is an association between television viewing time and the risk of obesity. A review found 63 of 73 studies (86%) showed an increased rate of childhood obesity with increased media exposure, with rates increasing proportionally to time spent watching television (Halton and HU, 2004)

Other illnesses

          Certain physical and mental illnesses and the pharmaceutical substances used to treat them can increase risk of obesity. Medical illnesses that increase obesity risk include several rare genetic syndromes as well as some congenital or acquired conditions: hypothyroidism, Cushing's syndrome , growth hormone deficiency,[Furtado et al., 2008] and the eating disorders: binge eating disorder and night eating syndrome. However, obesity is not regarded as a psychiatric disorder, and therefore is not listed in the DSM-IVR as a psychiatric illness. The risk of overweight and obesity is higher in patients with psychiatric disorders than in persons without psychiatric disorders (Appel et al., 2005).

            Certain medications may cause weight gain or changes in body composition; these include insulin, sulfonylureas, thiazolidinediones , atypical antipsychotics , antidepressants , steroids, certain anticonvulsants (phenytoin and valproate), pizotifen , and some forms of hormonal contraception.

1.2.2 GENETIC CAUSES OF OBESITY

           This occurs when an individual is born with the tendency to obesity, in which case the individual have genes that determine increased fat storage which in turn leads to obesity (Herrera and Lindgren, 2010).

           Like many other medical conditions, obesity is the result of an interplay between genetic and environmental factors. Polymorphisms in various genes controlling appetite and metabolism predispose to obesity when sufficient food energy is present. As of 2006, more than 41 of these sites on the human genome have been linked to the development of obesity when a favorable environment is present. [119] People with two copies of the FTO gene (fat mass and obesity associated gene) have been found on average to weigh 3–4 kg more and have a 1.67-fold greater risk of obesity compared with those without the risk allele. [120] The differences in BMI between people that are due to genetics varies depending on the population examined from 6% to 85% (Herrera and Lindgren, 2010).

1.3 SYMPTOMS OF OBESITY

The primary warning sign of obesity is an above-average body weight. But other signs includes

1.     Trouble sleeping

2.     Sleep apnea. This is a condition in which breathing is irregular and periodically stops during sleep.

3.     Shortness of breath

4.     Varicose veins

5.     Skin problems caused by moisture that accumulates in the folds of your skin

6.     Gallstones

7.     Osteoarthritis in weight-bearing joints, especially the knees

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