There are many different ways to classify obesity. In accordance with endocrine and pathogeny of the metabolic disease, obesity can be divided into simple obesity, secondary obesity and drug-induced obesity.
Types of Obesity
- Simple obesity
The simple obesity, called as primary obesity, is due to excessive energy intake and too little consumption , also known as diet-induced obesity and has the largest proportion in all types of obesity. About 95% of obese patients are of this type. The simple obesity are generally caused by the heredity factor, the nutrition surplus and a lack of exercise, and characterized by the even distribution of the whole body fat, many obese people in the family obesity , no special pathogeny which possibly cause obesity.
Simple obesity is a special disease that is different from secondary obesity. The exact pathogenesis of this obesity is not very clear, but it is certain that any factor likely cause simple obesity as long as they can make energy intake more than energy consumption. These factors include eating too much, too little physical activity, psychosocial factors, genetic factors, neuroendocrine factors and so on.
- According to the change of pathology, simple obesity can be classified as “hypertrophic fat” and “corpulent obesity.”
a. Hyperplastic obesity. Not only the size offat cells of become larger, but also the number of fat cells increase.
b.Corpulent obesity. Only the size of fat cells become larger, but the number are unchanged.
B.According to the age of suffering from this disease, simple obesity can be divided into ” juvenile onset obesity” and “adult onset obesity.”
- Juvenile onset obesity. It is also called constitutional obesity. Due to excessive nutrition during infancy,the number and the volume of fat cells increase, resulting in the obesity. These patients are fatter than their peers since childhood, so they are referred to as juvenile onset obesity. If we do not control the situation, the degree of obesity will be very severe, and obesity can even last a lifetime. Such obesity is not sensitive to the therapy of diet weight loss, and some patients may have a hereditable tendency. From this point,the concept of Chinese people to have a fat new born baby need to do some what change.
- Adult onset obesity. It is also known as acquired obesity or exogenous obesity. It is induced by the increase of the volume of the fat cells because of excessive nutrient after age 20 to 25. The reason why lots of women become obese or have shape deformation is that they pay no attention to control diet after middle-age. Generally speaking, the number of fat cells in obese body of this type does not increase ,but the size increase. Patients who are suffering from acquired obesity generally prefer to eat sweets or fried foods. Such patients are often become obese in adulthood because of excessive nutrition that they are referred to as adult onset obesity. While the therapy of diet weight loss can effectively control the development of acquired obesity.
- According to fat distribution in the different parts of the body, simple obesity can be classified as “abdominal obesity” and ” pygal obesity.”
- Abdominal obesity. The fat of this type patients mainly accumulates beneath the skin of the abdomen and within abdomen. The fatest part of the body is the abdomen, waist is often bigger than the hip, limb is relatively slenderer — these are common character of the obesity of adult male, so it is also known as the centripetal obesity, male pattern obesity and visceral obesity. From the nappearance, these patients are always with obese abdominen like an apple, therefore it is also called “apple-type obesity.”
- Pygal obesity. The fat of these patients generally distribute uniformly, and the fat in the hip is significantly more than the abdominen. The fatest part of the body is the buttocks, and the hip of the patient is bigger than waist — these are common in women, therefore, it is also known as non- centripetal obesity and female obesity. From the appearance, patients with pygal obesity are like pear, so it is also called “pear-shaped obesity”, which have smaller harm than the apple-type obesity.
Compared with pygal obesity , abdominal obesity have higher risk of suffering from complications. someone observed a group of white women, and found that the risk of suffering from diabetes of the obese people was 3.7 times higher than that of ordinary people, and the possibility of women with abdominal obesity to suffer from diabetes was 10.3 times higher than that of ordinary women. Of course, compared with non-obese people, pygal obesity are still very harmful while the harm is slightly smaller than abdominal obesity. It should be noted that we can not interpret above terms too literally, for example, male-type obesity is not particular to the males, and there are plenty of women with abdominal obesity, in other words, women can also have male obesity.
- Secondary obesity
Secondary obesity is metabolic disorder resulted by endocrine or metabolic obstructed diseases and genetic diseases. Obesity is only clinical symptoms of patients , while close scrutiny reveals patients with symptoms in addition to obesity and at the same time a variety of clinical manifestations, such as Cushing’s disease, hypothyroidism, pancreatic β – cell tumors, gonadal dysfunction, polycystic ovary syndrome, morgangni-stewartmorel syndrome.
To the secondary Obese patients, if primary diseases can not get effective treatment, symptom of obesity can not be significantly improved, so the treatment of secondary obesity is mainly to treat primary diseases, such as exercise and diet weight loss methods are unsuitable.
Secondary obesity can be subdivided into the hypothalamic obesity, pituitary obesity,, pancreatic obesity, hypothyroid obesity, adrenal dysfunction obesity, sexual gland dysfunction obesity and so on.
- Hypothalamic obesity
Causes: there are two types of nerve nuclei in hypothalamus regulating food intake. One is ventromedial nuclei as satiety center to send out a sense of satiety to antifeedant when excited. Another is ventral lateral nucleus as hunger center to increase appetite when excited. They can mutually adjust and restrict each other and is in a state of dynamic equilibrium under the physiological condition to make the appetite in the normal range and maintain normal body weight. When hypothalamic lesions occurr, such as inflammation, trauma, a new bio-stimulation and other pathological changes, the satiety center of ventromedial nuclei is damaged, so it can not restrict the hunger center of the ventral lateral nucleus. Then it will occur some clinical symptoms such as good appetite and easy hunger, so we will take in a large number of food , resulting in obesity.
Symptoms: Patients with hypothalamic obesity may have symptoms such as fatigue, lethargy, sexual dysfunction.
The most common pathogeny of hypothalamic obesity in children is craniopharyngioma, in adults inflammation, trauma and new bio-stimulation. The main treatment is to deal with the primary disease which causes hypothalamic obesity.
- Pituitary obesity
Causes: Pituitary obesity is induced by pituitary dysfunction and belong to hypothalamic syndrome. The causes are due to pituitary dysfunction, resulting in the decreased secretion of growth hormone, corticotropin, thyroid-stimulating hormone, so that the rate of metabolism decline, body fat decomposition reduce, synthesis increase.
Symptoms: Hyperplasia and hypertrophy of body bone, soft tissue and internal organs.
- pancreatic obesity
Causes: excessive secretion of insulin and the decrease of metabolic rate lead to the decrease of lipolysis while the increase of synthesis.
Symptoms: obese at every pore.
- Hypothyroid obesity
Symptoms: obesity and mucus-type edema.
- sexual gland dysfunction obesity
Causes: the Cerebral obesity, accompanied by the loss of sexual function, or loss of libido.
Symptoms: breast, lower abdomen, near the genitals of obesity.
(3) Drug-induced obesity
Sometimes in order to treat diseases clinically, doctors may give patients with long-term use of certain drugs that can easily lead to obesity at whiles with a little mistake. For example, the application of adrenal cortex hormones drugs (such as prednisone, dexamethasone and hydrocortisone, etc.) to treat anaphylactic disease, rheumatoid arthritis, bronchial asthma and other diseases, can also lead to obesity; drugs for mental disease like the phenothiazine drugs, can also induce sexual dysfunction and obesity. Patients with this type of obesity take up the proportion about 2 percent. In general, when patients stop using these drugs, obesity will disappeare by itself. But unfortunately, some people even develop into a patient with “refractory obesity”. So some people classify drug-induced obesity into secondary obesity.
How does one assess degree of Obesity?
One can access the degree of obesity based on following parameters
1] BMI: – It is the ratio of Height in Square centimeters and Weight in Pounds.
BMI less than 18.5 indicates under weight, BMI between 18.5 to 24.9 indicates Healthy weight, while BMI between 25 to 29.9 refers to Overweight and BMI more the 40 is indicating Morbidly obese.
2]Waist Circumference:- Women with a waist measurement of more than 35 inches and men more than 40 inches may have higher chances of diseases than people with smaller waist measurements.
3] Waist to Hip Ratio: – Waist-hip ratio or waist-to-hip ratio (WHR) is the ratio of the circumference of the waist to that of the hips. Males with a Waist to hip ratio of more than 1 while females of more than 0.85 are at a higher risk.
4] Skin Folds Thickness: – This refers to the measurement of subcutaneous fat located directly beneath the skin by grasping a fold of skin and subcutaneous fat and measuring it using calipers. It is used mainly to determine relative fatness and the percentage of body fat.
The Obesity Problem
There are a multitude of health complications from obesity.
How does obesity occur? The formula is simple:
Food eaten – Exercise = Weight Gained
Another way of explaining the situation:
Delicious, Calorie Dense Food + Sedentary Lifestyle = Obesity
Most people live in a food toxic environment and are bombarded by cues to buy and eat food throughout the day. In addition, stress drives overeating.
Stress + Abundant Food = Obesity
There is ordinarily a modest amount of calories burned to maintain normal body metabolic processes. In general, for a normal healthy adult to maintain body weight with just activities of daily living, caloric intake must be limited to 10 calories (kcal) per pound (22 calories per kg). Thus, a 150 lb (68 kg) person needs about 1500 calories (kcal) per day to avoid gaining weight. Exercise can increase caloric use, and exercise has a “carryover effect” to increase metabolism and burn more calories after exercise. Of course, growing children require more calories. (Willett et al, 1999).
Exercise can burn calories (average for a standard 70 kg person) as follows:
Here’s a concept: eat one less…do one more. Over time, reduce intake and increase activity.
Eat one less: helping per meal, meal per week, snack per day, etc.
Do one more: day with exercise, hour of exercise, repetition of activity, etc.
Here’s another concept, especially for kids: go outside.
Why stare at pixels jumping around the screen of an electronic device when there are creative and rewarding activities to be accomplished with physical activity. Get a life.
Just brisk walking for 20 minutes a day can have major benefits. A good aerobic exercise with cardiovascular benefit is to climb 10 flights of stairs once a day. Increase by one flight per week to achieve the goal.
Young adults can generally eat more and not gain weight, but metabolism tends to slow in the mid-30’s (and middle-aged people become more inactive), so that is when many adults begin to gradually gain weight. One pound (0.45 kg) of fat has 3500 kcal. An excess intake of only 0.3% of calories eaten translates into a 20 pound (9.1 kg) weight gain over the age range of 25 to 55 years. The average weight gain in young adults averages 0.2 to 0.8 kg per year.
The body mass index (BMI, defined below) may be related to multiple genetic factors in 30 to 40% of persons, and this may in part determine the fat distribution. Single gene defects that produce a defined disease marked by obesity, such as the Prader-Willi syndrome, are extremely rare. (Rosenbaum et al, 1997)
Food intake is regulated via neural circuits located in the hypothalamus. A hormone produced in adipocytes (fat cells) known as leptin has the function of informing the hypothalamus about the state of fat stores. Leptin inhibits food intake and increases energy expenditure via an interaction with specific leptin receptors located in the hypothalamus. Differences in leptin levels may explain differences in BMI. (Baskin et al, 1999)
Social factors play a major role in weight gain. Situations during life in which weight gain is more likely to occur include: adolescence, pregnancy, mid-life in women, and following marriage in men. Persons who emigrate to a more urbanized culture tend to gain weight. Behavioral or environmental changes in life, such as smoking cessation, are associated with weight gain. Weight gained during holiday periods and festivals is more than at other times of the year and tends not to be lost. The chance of becoming obese increases by 57% if one has a friend who becomes obese in a given interval. Among pairs of adult siblings, if one sibling becomes obese, the chance that the other becomes obese increases by 40%. If one spouse becomes obese, the likelihood that the other spouse becomes obese increases by 37%.
What are the Risks?
Obesity is measured most accurately by calculating the body mass index, or BMI. The BMI is calculated as follows:
Body Mass Index = weight in kg / height in meters2
An ideal body mass index (BMI) is in the range of 20 to 24 and anything above or below that range will increase certain risks for morbidity and mortality. In general, a BMI >28 increases the risk for morbidity. A third of the U.S. adult population qualifies as obese, defined with a BMI of 30 or more, while half are defined as overweight by a BMI 25 or more. (Note: this tutorial’s author’s BMI is 21.5)
However, the distribution of fat has importance in determination of risk. A central distribution of fat, as is more typical of men, carries a higher risk for morbidity. A more peripheral distribution, as in hips and thighs in women, carries a lesser risk. The risk can be determined by measuring waist circumference and by calculating a waist-to-hip circumference ratio. In general, a waist:hip circumference ratio >0.9 for men and >1.0 for women carries an increased risk for morbidity. (Pischon et al, 2008)
Another risk is the time of onset of obesity. Obesity in childhood increases the risk for morbidity, regardless of whether obesity persists into adulthood.
Risks for morbidity are increased as follows when the BMI is 26, versus 21:
|Sex||Diabetes Mellitus||Hypertension||Coronary Artery Disease||Cholelithiasis|
|Women||4||2 – 3||1.5||2 – 3|
|Men||8||2 – 3||2||2 – 3|
The relationhip between BMI and all-cause mortality has been shown in a large study involving nearly 1.5 million White persons in the U.S. The table below gives the estimated hazard ratios for death (larger number is worse) from any cause for persons who never smoked, according to BMI category: (Berrington de Gonzalez et al, 2010).
|Hazard Ratios, Deaths from Any Cause|
|15 – 18.4||1.47||1.37|
|18.5 – 19.9||1.14||1.01|
|20 – 22.4||1.00||1.00|
|22.5 – 24.9||1.00||1.00|
|25 – 27.4||1.09||1.06|
|27.5 – 29.9||1.19||1.21|
|30 – 34.9||1.44||1.44|
|35 – 39.9||1.88||2.06|
|40 – 49.9||2.51||2.93|
This study shows that risk for death from cancer and from cardiovascular disease increases with BMI.
Specific Health Risks with Obesity
There are some diseases that are seen with increased frequency in persons who are obese, including certain types of cancer, diabetes mellitus, coronary artery disease, stroke, hypertension, cardiomyopathy, non-alcoholic steatohepatitis, osteoarthritis, reproductive problems, sleep apnea, and gallbladder disease.
The following cancers are seen with increased frequency in persons who are overweight:
A third to half of cases of endometrial carcinoma occur in women with a BMI >29. Breast cancer risk is increased with obesity only for women who are postmenopausal. Half of cases of breast carcinoma in postmenopausal women occur in association with a BMI of >29. Risks for cancers of the lung, colon/rectum, and breast are diminished with healthy lifesytle/dietary patterns. (National Task Force, 2000) (Mai et al, 2005)
For persons who are grossly overweight (BMI >40) the risks are greater, with death rates from all cancers for men more than 52% and for women more than 62% greater than in persons of normal weight. The range of cancer types is broad, including esophagus, colon, rectum, liver, gallbladder, pancreas, kidney, non-Hodgkin lymphoma, and multiple myeloma in both men and women. In, prostate and stomach cancers are more frequent with increasing BMI, while in women breast, uterus, cervix, and ovarian cancers are more frequent. (Calle et al, 2003)
In the U.S. there are 15 to 16 million adults who have diabetes mellitus, or about 8% of the population 20 years or older in age. Of these, 90 to 95% are classified as diabetes mellitus type II (DM type II), the type associated with obesity. About 80 to 90% of persons with type II diabetes mellitus are obese. About two-thirds of persons with DM type II have a BMI of at least 27, and half of persons with DM type II have a BMI of at least 30. (National Task Force, 2000)
The prevalence of DM type II in the U.S. increased by 25% in the last decade of the 20th century.
Among persons with a BMI >30 who already have impaired glucose tolerance and are at risk for developing type II diabetes mellitus, adopting lifestyle changes that decrease weight, decrease consumption of saturated fats and sugar in the diet, and increasing exercise will reduce the risk for type II diabetes mellitus by over 50 to 60%.
A characteristic pathologic finding in the islets of Langerhans of the pancreas can be seen in association with type II diabetes mellitus. A major complication of diabetes mellitus results from the accelerated, advanced atherosclerosis.
The global epidemic of obesity and diabetes mellitus has led to a marked increase in the number of persons worldwide with metabolic syndrome. Both type 2 diabetes mellitus and metabolic syndrome share common features, and patients may be defined as having one or both. Metabolic syndrome, also known as syndrome X, or the insulin resistance syndrome, is defined as follows (Eckel et al, 2010):
Diabetes or impaired fasting glycaemia or impaired glucose tolerance or insulin resistance, plus 2 or more of the following:
- Obesity: BMI > 30 or waist-to-hip ratio > 0.9 (male) or > 0.85 (female)
- Dyslipidemia: triglycerides = or > 150 mg/dL or HDL cholesterol < 35 (male) or < 39 (female) mg/dL
- Hypertension: blood pressure > 140/90 mm Hg
- Microalbuminuria: albumin excretion > 20 mg/min
Patients with both type 2 diabetes and the metabolic syndrome are at increased risk for cardiovascular complications from both arerial and arteriolar disease. They should be treated to keep the Hgb A1C under 7% (Tuomilehto et al, 2001).
Therapeutic goals and recommendations include:
- Lose 10% of body weight over the first year through lifestyle modifications with diet and exercise, thereafter continue weight loss or maintain weight.
- Institute a regular program of physical activity that includes 30 to 60 minutes of moderate-intensity exercise daily.
- Reduce intake of saturated fats, trans fats, and cholesterol.
- Stop smoking
Coronary Artery Disease
Persons with diabetes mellitus are at increased risk for accelerated and advanced atherosclerosis that increases the risk for coronary artery disease that can lead to myocardial ischemia and myocardial infarction. However, even obese persons who do not have hyperglycemia can have an increased risk for coronary atherosclerosis. Obese persons have a >50% risk for a total serum cholesterol >250 mg/dL. In contrast, a study of middle-aged women revealed that those who did not smoke, were not overweight, maintained a healthy diet, and exercised at least moderately for a half hour each day had an incidence of coronary events 80% lower than the rest of the population. (Stampfer et al, 2000)
Atherosclerosis is potentially reversible. Adoption of major lifestyle changes including diet and exercise in middle aged adults can lead to lowering of LDL cholesterol levels by 37% in just one year and reduce the amount of coronary arterial stenosis. (Ornish et al, 1998)
Hypertension and Stroke
The rate of ischemic cerebrovascular disease is 75% higher in women with a BMI >27 and 137% higher in women with a BMI >32, compared to women with a BMI of 21 or less. Though not included in this study, risks for men are increased as well. (National Task Force, 2000)
The prevalence of cardiovascular diseases and their complications increases as the amount of dietary sodium increases. It is estimated that if adults from 40 to 85 years of age in the U.S. were to decrease sodium intake by just 9.5%, there would be 1 million fewer deaths and $32 billion saved in health care costs over their lifetime. (Smith-Spangler et al, 2010)
Some obese patients who have little or no coronary artery disease and do not have a history of hypertension may still develop heart failure. In these patients, the heart is globally enlarged, similar to a dilated cardiomyopathy. If such persons lose weight, the heart diminishes in size. This obesity cardiomyopathy may be related to blood volume expansion or other factors. (Dela Cruz and Matthay, 2009)
Non-alcoholic Fatty Liver Disease (NAFL)
NAFL is being recognized more frequently. Dietary patterns play a role in the development ofsteatosis (fatty change) in the liver. Obesity increases the risk for alterations in hepatocyte function that lead to accumulation of lipid in hepatocytes and hepatomegaly. NAFL reduces the metabolic function of the liver. NAFL can proceed to non-alcoholic steatohepatitis (NASH), to liver failure, and even cirrhosis, with an increased risk for development of hepatocellular carcinoma. (Choudhury and Sanyal, 2004)
Increased weight will increase the stress on weight-bearing joints, particularly lower extremities, leading to osteoarthritis. A BMI of 30 or more markedly increases the risk for osteoarthritis of the knees. Interestingly, obese persons are less likely to have osteoporosis, but osteoarthritis more than makes up for this.
Women who are obese are more likely to have menstrual irregularities and ovulatory infertility, including the polycystic ovarian syndrome (PCOS). Women with PCOS typically have irregular bleeding, hirsutism, and/or infertility in association with chronic anovulation and androgen excess not attributable to another cause. PCOS is estimated to occur in 4% of women, but there is an increased prevalence with diabetes mellitus and obesity. Conversely, women with PCOS are more likely to have obesity and diabetes mellitus. PCOS is characterized by insulin resistance, hyperandrogenism, and abnormal gonadotropin release with inadequate follicle stimulating hormone release, leading to anovulation. Weight loss can aid in treatment of PCOS. (Guzick, 2004)
Obesity in women who are pregnant increases the likelihood for gestational diabetes that can affect the developing fetus. Maternal obesity increases the risk for macrosomia, stillbirth, and neural tube defects. The increased maternal risks include hypertension, pre-eclampsia, and hemorrhage. (Dixit and Girling, 2008)
Obstructive Sleep Apnea
Persons who are obese have a greater likelihood for obstructive sleep apnea (OSA), or periods of absent breathing while asleep. OSA is the major feature of obesity hypoventilation syndrome, which is defined by a body mass index of 30 or more along with sleep-disordered breathing and chronic daytime alveolar hypoventilation with PaCO2 of 45 mm Hg or more and PaO2 less than 70 mm Hg. Persons who snore while sleeping have a propensity to develop sleep apnea. The increased soft tissue in upper airways contributes to the problem. Sleep apnea is accompanied by decreased ventilation (hypoventilation) and pulmonary dysfunction. (Littleton and Mokhlesi, 2009)
Biliary tract lithiasis, manifested mainly by development of cholelithiasis (gallstones), is more likely to occur in persons who are obese. The gallstones are typically of the mixed type with cholesterol. Cholelithiasis can lead to cholecystitis and to pancreatitis.
What Can Be Done?
The best approach is prevention. Adopting a lifestyle that includes a healthy diet and exercise will prevent obesity from happening. Losing weight once it has been been gained is difficult, but worth trying for health benefits.