With affluence and sedentary life-styles, obesity is emerging as a serious problem all over the world. It is defined as accumulation of excess body fats. The fat accumulation occurs mainly in abdomen (called visceral fat) or beneath the skin (called subcutaneous fat). High calorie consumption with inadequate exercise is the root cause of obesity.Both are associated with the present day life-style where consumption of junk food has increased and people are becoming more lazy, moving around much less than before.
In an obese person, the two parameters show rise. The first is body mass index (BMI), which exceeds 30 kg/m2 and the second is measure body-weight. In an obese person, it exceeds 20% or more than ideal body weight (IBW). These terms are explained separately in a box towards end of this article.
Causes of obesity
Obesity is one of the most serious problems among urban affluent population. As mentioned above, it develops because of sedentary lifestyle characterized by excessive calories coupled with inadequate exercise. Even in cases where daily intake exceeds the body requirements marginally, obesity develops over a prolonged time period.
But obesity is not a simple problem of excessive calories; some persons who observe dietary precautions and are reasonably active tend to gain weight. This clearly indicates that several other factors contribute to development of obesity.
Genetic predisposition plays an important role. For examples, obesity has been observed to run in family. If one parent is obese, 40%–50% chances are there that the children would also suffer from obesity. And if both parents are obese, chances are much higher.
Thus, genetic predisposition has been suggested based on the familial incidence of obesity. However, no single gene is responsible for obesity.
It is a group of proteins that influences appetite-control system in the brain. These proteins cause decreased food intake, thus representing ‘satiety signal’ in the body. Deficiency of leptins in mice were reported to lead to overeating and development of obesity. When injection of leptins is given to these animals, they tend to eat less and lose weight. These experimental findings bring out role of leptins in arresting diabetes.
Certain metabolic diseases are known to be commonly associated with obesity. These are:
- Hypothyroidism- the thyroid gland becomes slow.
- Type 2 diabetes: Obesity may be cause or consequence of insulin resistance and diabetes. Such people are at great risk of developing high blood pressure and heart diseases.
- Hypogonadism, Cushing syndrome and hypopituitarism are hormonal diseases that lead to obesity.
- Women are more prone to become obese during puberty, during pregnancy and after menopause.
Table 1 Body Mass Index (BMI) in Normal and Overweight States
- Serum lipid profile gets deranged. Some of the dangerous lipids, which lead to heart attack, are present in increased concentrations in blood of obese persons. Examples include elevated free fatty acids, triacylglycerols, total cholesterol and LDL levels. These parameters respond poorly to dietary manipulations.
- Insulin resistance occurs, which means that the obese persons respond poorly to insulin. As a result insulin becomes less effective/ or ineffective in obese persons. The condition is termed as insulin-resistance and hyperinsulinaemia, which leads to several dangerous consequences.
Dangerous consequences of Obesity
Obesity is associated with increased risk of several medical and surgical problems.
- The major ill effects of obesity are reduced lifespan and coronary heart disease (CHD), because of deranged lipid profile. Obese individuals are at a higher risk of developing diabetes; nearly 80% of the adult-onset diabetic individuals are obese. The insulin receptors are decreased because of down-regulation, resulting in decreased sensitivity to insulin. This in turn leads to hyperglycaemia and hyperinsulinaemia is the natural consequence. Hyperinsulinaemia in turn causes stimulation of sympathetic nervous system, which results in vasoconstriction and retention of sodium and water. Both these changes lead to hypertension.
- The obesity is also linked with respiratory symptoms and diseases, including exertional dyspnea, obstructive sleep apnea syndrome (OSAS), obesity hypoventilation syndrome (OHS), chronic obstructive pulmonary disease (COPD), asthama, pulmonary embolism, and aspiration pneumonia. Each one of these conditions is serious and potentially lethal, as illustrated by the following examples:
- Obese person is out-of-breath after walking a short distance or climbing a few steps (exertional dyspnea)
- Snoring is common problem among obese persons. It may lead to sudden stopping of breath and the person may die in his sleep ( OSAS).
- The obesity can also impair cognition and motor performance through altering brain functions.
- Orthopaedic diseases are common in obese people. The persons going for knee-replacement surgery, for example, are more often overweight.
- The metabolic dysfunction, dyslipidemia, and inflammation caused by obesity contribute to the development of a wide variety of disorders and effects on the nervous system. In the CNS, mild cognitive impairment can be attributed to obesity – induced alterations in hippo campal structure and function in some patients.
The best treatment for the obese individuals – in fact the only effective mode of treatment – is reduction of body weight. All the aforementioned metabolic changes get significantly reversed if the IBW is attained.
This goal can be accomplished by reducing the intake of calories and performing controlled exercise. Frequent small meals with lots of vegetables have been found to be especially effective. A fat-restricted diet may retard the ageing process also and thus prolong the lifespan. Surgical intervention (bariatric surgery) is useful in some cases.
A low-calorie diet contains around 1200-133 kcal/day. In addition to diet and exercise, a behaviour intervention is equally important for relapse avoidance.
BENEFITS OF WEIGHT REDUCTION
Diet and Coronary Heart Disease
CHD is a potentially lethal condition; the mortality is very high if timely diagnosis is not made and proper treatment is not initiated. The underlying defect in CHD is deposition of atherosclerotic plaques on the inner surface of the small- and medium-sized arteries. A plaque consists of deposits of cholesterol, cholesterol esters and cellular debris.
As the disease progresses, these deposits reduce or even block the blood flow. The blood supply to the peripheral tissues is impaired resulting in inadequate supply of oxygen and nutrients to these tissues. The consequences may be hazardous, such as myocardial infarction and stroke.
Several dietary factors are thought to influence the incidence of coronary artery disease, most notably cholesterol. LDL cholesterol is bad cholesterol, whereas HDL cholesterol is cardioprotective. Relatively higher HDL levels are seen in women before menopause, which may account, in part, for a lower incidence of CHD in them.
Bearing in mind the above-mentioned correlations, the following measures are advised in the susceptible individuals:
1. Reduction of Dietary Intake of Cholesterol
Cholesterol, being a product of animal metabolism, is found only in foods of animal origin; egg yolk and organ meats are extremely rich sources. In contrast, the plant products – even vegetable oils – contain no cholesterol. In view of these facts, necessary dietary modifications must be made in diet so that intake of cholesterol-rich foods is reduced.
2. Change in Lifestyle
It should be in such a way that adequate physical exercise becomes part of daily routine.
3. Increased Dietary Intake of Fibres
There should be increased dietary intake of fibres, although the exact role of a high-fibre diet on coronary artery disease is still controversial. Mode of action of fibres and their beneficial effects have already been discussed in this chapter.
4. Increased Intake of Dietary Antioxidants
There should be increased intake of dietary antioxidants, such as vitamins C and E, and β -carotene. These compounds chemically inactivate the oxidative radicals derived from molecular oxygen and hence protect LDL against oxidation. This offers protection against heart diseases as confirmed by certain studies which reported that daily intake of 100 international units of vitamin E (RDA 15 IU) may reduce death from coronary artery disease by approximately 40%.
5. Hypolipidaemic Drugs
These are usually recommended in middle-aged men for reducing cholesterol and triglyceride levels.
Definitions of obesity are arbitrary and are based upon estimates of the following:
(i) Ideal body weight (IBW): Ideal body weight is defined as the body weight associated lowest morbidity and mortality. It depends on the height of the individual. When the actual body weight is upto +20% of the IBW, the condition is overweight. When it exceeds the +20%, the condition is termed obesity. Underweight refers to the body weight that is 80% of IBW, or more commonly, when it falls below the lower end of the acceptable range of IBW.
(ii) Body mass index (BMI): Another way of defining obesity is by the measurement of the BMI, which is defined as weight (Kg) divided by height2 (meter2). BMI is well correlated with measures of body fats of an individual. The acceptable range is 20-30 Kg per meter2. Obesity refers to a state when BMI is more than 30 Kg/m2.
(iii) Skinfold thickness: the subcutaneous deposition of the fat results in the increase of the skinfold thickness. Thus, measurement of skinfold thickness is also an indicator of body fat stores.
- By Dr Parul Gupta