obesity in the elderly
Introduction
Introduction to obesity in the elderly Obesity is a pathological condition in which the number of fat cells in the body is increased or the volume is enlarged to cause excessive accumulation and/or abnormal distribution of fat in the body, and the body weight exceeds 20% of the standard body weight. On the other hand, obesity is a complex of many complicated situations, such as it needs to be combined with type 2 diabetes, hypertension, dyslipidemia, ischemic heart disease, etc., so it is a chronic metabolic abnormal disease. No obvious cause can be called simple obesity, obesity can also be used as a clinical manifestation of certain diseases (such as hypothalamic-pituitary inflammation, tumor, trauma, Cushing's syndrome, hypothyroidism, hypogonadism) First, also known as secondary obesity, obesity in the elderly refers to the presence or presence of obesity in the elderly over 60 years of age. basic knowledge The proportion of illness: 10% Susceptible people: the elderly Mode of infection: non-infectious Complications: fatty liver, cerebral arteriosclerosis, hypertension
Cause
The cause of obesity in the elderly
Genetics (20%):
Previous studies have found that single-gene and multi-gene defects in obese animals, and human epidemiological studies have shown that simple obesity can present a family predisposition, but the genetic basis is unclear, and its common lifestyle factors (such as food preferences) cannot be ruled out. Simple physical activity, etc., simple obesity with clinically suspected chromosomal abnormalities is limited to several rare hereditary diseases such as Laurence-Moon-Biedl syndrome and Prader-Willi syndrome.
In 1994, obese gene (Ob gene, also known as leptin gene, OB for short) was successfully cloned. OB and its expression product leptin (Leptin) became a research hotspot. Leptin is a protein hormone secreted by adipose tissue. Containing 146 amino acids with a molecular weight of 16KD, it has a wide range of physiological effects. By regulating the balance of energy metabolism, the amount of body fat is relatively constant. When food intake increases and fat storage increases, leptin secretion increases, and a series of reactions occur through the hypothalamus. Decreased appetite, increased energy consumption, increased sympathetic excitability, etc., increase fat breakdown, decrease synthesis, and increase body weight. When the body is starving, leptin secretion is reduced, and a series of protective responses occur through the hypothalamus. If the appetite increases, the body temperature decreases, the energy consumption decreases, and the parasympathetic nerve excitability increases, so as to maintain the body weight does not reduce too much. Ob/ob obesity is caused by the O mutation, which causes leptin deficiency, and the administration of exogenous leptin can Reduced food intake, increased energy consumption, weight loss, and simultaneous correction of hyperinsulinemia and hyperglycemia, but in the study of human obesity In addition, only a few obese families have caused leptin deficiency due to OB mutation, or the receptor is not sensitive to leptin due to mutation of the leptin receptor gene. In addition to the hypothalamus, leptin receptors are also widely present. Central and external organs, therefore, for most obese patients, the relative lack of leptin or leptin resistance, and its mechanism, is not yet clear, and further research is needed.
Central nervous system (10%):
The central nervous system can regulate appetite, digestion and absorption of nutrients, and electrical stimulation of the ventromedial nucleus of the hypothalamus in experimental animals can cause food refusal, while electrical or chemical destruction of the area causes polyphagia, hyperinsulinemia and obesity, clinically Inflammation of the hypothalamus or limbic system can also be seen, tumors, trauma, surgery-induced obesity, regulation of feeding has both short-term and long-term effects, short-term effects include the effect of satiety signals during meal and between, in the gastrointestinal tract Muscle stretch receptors, chemoreceptors and osmotic receptors send signals to the central nervous system through the nerves and body fluids to regulate appetite, while long-term effects are related to stable body weight. In clinically, simple obese patients may not have Hypothalamic lesions, appetite is also affected by the spirit.
Endocrine system (30%):
Simple obesity patients have endocrine function changes, elderly obese patients, obese rodents (whether hereditary or injured hypothalamus) can see elevated blood insulin, suggesting that hyperinsulinemia can cause more food, form obesity, some nerves Peptides and hormones (including cholecystokinin, bombesin, motilin, somatostatin, insulin, endorphin, neuropeptide Y, galanin, serotonin, catecholamine, r-amino acid, etc.) The effect of eating, the majority of obese women in the elderly, especially after menopause, suggest that there may be a relationship with hormones.
Metabolic factors (20%):
It is speculated that there are metabolic differences between obesity and non-obesity. For example, obesity nutrients may be more likely to enter the fat production pathway; the effect of adipose tissue ingesting energy from nutrients is enhanced to increase triacylglycerol synthesis and storage; The acylglycerol mobilization was blocked, there was no significant difference between the basal metabolic rate of obesity and non-obese people and the heat-generating effect caused by diet. There is still no evidence that obesity does have the energy utilization and storage efficiency caused by basic metabolic defects.
Other factors (10%):
It is believed that obesity is related to nutritional factors. With excessive intake of calories, fat synthesis increases. Excess calories are stored in adipose tissue in the form of triacylglycerol, which forms obesity. Eating more can occur at any age, but young people start eating more. It is of great significance for the occurrence of obesity in the elderly. Some studies have pointed out that elderly people with obesity consume less calories per day than non-obese people. Therefore, some obesity is considered to be due to decreased physical activity, but insufficient physical activity may be obese. Consequences or only participate in the maintenance of obesity and development rather than specific causes.
Old age obesity is also associated with abnormal brown body fat (BAT) function. BAT is named for its vascular distribution and is rich in cytochromes. It is mainly distributed in the interscapular region, around the pericardium and sinus node, and the aorta and sympathetic chain. Surrounding, related to heat production, it has recently been found that B3 adrenergic receptor (BB3AR) gene mutation is also associated with the occurrence of obesity. B3AR is mainly expressed in BAT, participating in energy balance and fat storage through its heat-promoting effect and promoting lipolysis. Adjustment.
Obesity in the elderly is also related to growth factors. The hypertrophy of adipose tissue can be caused by an increase in the amount of fat (proliferative type); an increase in the volume of fat cells (hypertrophy); or an increase in the number of fat cells and an increase in the size of hypertrophy. Most of the patients are hyperplasia or hypertrophy, the degree of obesity is heavier, and it is difficult to control. The adult onset is mostly hypertrophic. In addition, studies have found that maternal nutrition is not much in the fetus, lack of protein, or low birth weight. Infants, changes in the diet structure in adulthood, are also prone to obesity.
There is a view that each person's fat content and body weight are limited and regulated by a certain inherent control system. This level of regulation is called Set Point, and the setting point of elderly obese people is higher. This theory can explain It is difficult for obese people to lose weight, or even if weight loss is difficult to maintain, the specific link of the setting point is still unclear.
In short, modernization, civilization and changes in social and economic conditions have reduced the physical activity of the elderly and the westernization of the diet, the increase in saturated fatty acids, and the decrease in cellulose, coupled with the pressure from urban life, resulting in nutritional imbalances. , genetic factors, central nervous system abnormalities, endocrine dysfunction can lead to obesity in the elderly.
Pathogenesis
The cause of obesity in old age is not fully understood. There are various causes. The same patient may have several factors at the same time. In general, if the intake of calories exceeds the consumption of the human body, that is, no matter how much food, or consumption is reduced, Or both, can cause obesity.
Prevention
Elderly obesity prevention
1. The importance of tertiary prevention for obesity in the elderly
(1) Primary prevention: Also known as Universal Prevention, it is a measure for the population as a whole. It should stabilize the level of obesity and ultimately reduce the incidence of obesity, thereby reducing the prevalence of obesity, by improving dietary structure and promoting appropriateness. Physical activity, as well as reducing smoking and drinking, to change lifestyles, and ultimately reduce obesity-related diseases for universal prevention.
(2) Secondary prevention: Also known as Selective Prevention, the aim is to educate people at high risk of obesity so that they can fight against risk factors that may come from heredity and make them obese. Susceptible populations, Singapore's adoption of this preventive measure for children has reduced the prevalence of obesity from 15% to 12.5%.
(3) Tertiary prevention: Also known as Targeted Prevention, it is targeted at individuals who are already overweight or obese, but are still not obese, with the aim of preventing weight gain and reducing weight-related diseases. The prevalence, weight-related diseases, or cardiovascular disease, and individuals with high risk factors for obesity-related diseases such as type 2 diabetes should be the main target.
2. Risk factors and interventions
Studies have shown that the conversion of traditional high-carbohydrate, high-fiber diets to high-calorie, high-fat diets is one of the important environmental factors for obesity.
Insulin resistance (IR) is considered to be the basis of IGT and diabetes, hyperlipidemia, hypertension, and obesity. Studies have shown that excess fat storage (obesity) or excessive intake is associated with insulin resistance (IR), and different fatty acids in fat. The composition has different effects on IR. The classification of fatty acids is based on the presence or absence of double bonds in its hydrocarbon chain. It is divided into saturated fatty acids (SFA) without double bonds and monounsaturated fatty acids (MUFA) with one double bond. And polyunsaturated fatty acids (PUFA) containing multiple double bonds; polyunsaturated fatty acids (PUFA) are further classified into omega-3, omega-6 and other series of fatty acids according to the position closest to the double bond of the omega carbon atom, so-called omega-3 The series is a polyunsaturated fatty acid (PUFA) having a double bond at three positions such as the number of carbon atoms of .
Dietary saturated fatty acids (SFA) are mainly found in animal fats. In meat, the content of vegetable oil is very small. The main component of monounsaturated fatty acid (MUFA) is oleic acid, which is mainly found in olive oil (84%), followed by peanut oil. (56%), corn oil (49%), animal oil (30%), etc., omega-6 series polyunsaturated fatty acids (PUFA) are rich in vegetable oil, the main component is linoleic acid and peanuts transformed from it. Tetraic acid (AA), omega-3 series polyunsaturated fatty acids (PUFA) are mainly composed of 20 carbon 5-enoic acid (EPA) and 22 carbon 6 enoic acid (DHA), mainly derived from deep-sea fish, epidemiological studies. The San Luis Vallev Diabetes Study from the United States and the Dutch Chronic Disease Risk Factors Study found that saturated fatty acid intake is independent of fat, and body mass index (BMI) is positively correlated with fasting insulin levels (a hallmark of insulin resistance), while polyunsaturated fatty acids ( PUFA) intake is not associated with or negatively correlated with fasting blood insulin levels, suggesting that excessive intake of saturated fatty acids (SFA) is associated with hyperinsulinemia and insulin resistance (IR), so limiting dietary fatty acids to prevent obesity Critical, less physical activity Important environmental factors that induce obesity, the impact of physical vitality on insulin sensitivity, especially on skeletal muscle insulin sensitivity, has been confirmed by numerous clinical and laboratory, as well as in vivo and in vitro experiments, with less physical activity, meditation, and less movement. Lifestyle is associated with systemic insulin resistance, and insulin resistance is the basis of obesity. Conversely, physical activity, whether short-term or persistent, can increase insulin sensitivity, improve muscle, lipid and liver insulin resistance, and the benefits of exercise in addition to weight loss. It can increase systemic oxygen consumption, increase bone blood flow, increase glucose oxidation, increase lipolytic enzymes, especially hepatic lipase activity, increase HPL3C sub-component, lower TG, lower blood pressure.
Smoking is an independent risk factor for insulin resistance. Although smoking can cause weight loss and lead to a decrease in body mass index (BMI), long-term smoking can cause fat redistribution, waist circumference and waist-to-hip ratio (WHR) increase, resulting in intra-abdominal fat accumulation. To form abdominal obesity, interventions include:
1 pair of people who have not smoked should be prevented from smoking.
2 smokers stop smoking, can use drugs to quit smoking, that is, using oral, skin or nasal nicotine replacement therapy, establish an effective smoking cessation guarantee system, NHANESI study found that after stopping smoking, smokers increased the average weight by 6 to 10 pounds (1 Pounds = 0.4536 kg), weight gain may have a negative effect on smoking cessation, but studies have shown that the danger of continuing smoking is far greater than the risk of weight gain after smoking cessation.
3. Community intervention
Raising the awareness of obesity and its harm among the whole people is an important part of the prevention and treatment of obesity. Because China has been in a period of relatively lack of material for a long time, the rapid increase of obesity is only a phenomenon of nearly 20 years. People's understanding of obesity and its harm It is not enough. Some people even think that obesity is a healthy performance. Therefore, it is necessary to carry out health education in the whole society. In addition, maintaining normal weight is also a long-term need for certain perseverance to educate patients. To make it aware of obesity enough to persevere, the help and support of family members and the surrounding population to reduce weight in obese patients is also an important factor to help reduce weight. Therefore, it is very important to raise the awareness of obesity among the whole people. By relying on doctors to warn patients not to gain weight and not to prevent the prevalence of obesity, it is necessary to strengthen universal education and publicize the harmfulness of obesity in old age. In formulating policies for urban construction, transportation and housing planning, full consideration should be given to spontaneous sports activities. Demand and need to be promoted by public health experts and the health sector
Complication
Obesity complications in the elderly Complications, fatty liver, cerebral arteriosclerosis, hypertension
Skin wrinkles are prone to dermatitis, rubbing, and easy to combine with purulent or fungal infections, obesity chronic dyspepsia, fatty liver, mild to moderate liver dysfunction are also more common, concurrent with atherosclerosis, high blood pressure and so on.
Symptom
Obesity symptoms in the elderly Common symptoms Weight gain Anxiety Muscle soreness Depression Abdominal obesity Respiratory failure High fever Back pain Secondary obesity
Obesity caused by different causes has different clinical manifestations. Patients with secondary obesity have clinical manifestations of primary disease, and the distribution of adipose tissue blocks is gender-specific. Usually male-type fat is mainly distributed above the waist (also known as apple type). ), female fat is mainly distributed below the waist, such as the abdomen, buttocks, thighs (also known as pear type), apple type body is more dangerous than the pear type.
Older obesity patients may have body and mind-related inferiority, anxiety, depression and other physical and mental problems, but in behavior may cause shortness of breath, joint pain, edema, muscle aches, physical activity reduction, in addition, closely related to obesity The prevalence and mortality of some diseases such as cardiovascular disease, hypertension, and type 2 diabetes have also increased.
Type 1.2 diabetes
Studies have shown that obesity is an independent risk factor for type 2 diabetes. About 75% of obese people develop type 2 diabetes, and those with obesity are more likely to have insulin resistance (IR). In particular, abdominal obesity is more closely related to IR, due to intra-abdominal fat breakdown. The speed is faster than other parts, so the formation of abdominal obesity can be decomposed to produce a large amount of free fatty acids (FFA) and glycerol. As FFA uptake and oxidation increase, the oxidation of fat also increases, accompanied by sugar oxidation, reduction of sugar storage, insulin Mediated gluconeogenesis damage, decreased sensitivity of the liver and skeletal muscle to insulin, decreased insulin activity and increased secretion, eventually leading to IR and hyperinsulinemia, when B cells of obese patients can compensate for IR, Blood sugar can be normal. If you can't compensate, you will have high blood sugar and develop diabetes.
2. Hypertension
A large body of evidence indicates that obesity is an independent risk factor for hypertension. Clinical data show that BMI is significantly positively correlated with blood pressure. The relationship between blood pressure and body weight is already present in children and old age. Both obesity and hypertension have a family history and hypertension. Susceptible, obesity promotes the rise of blood pressure. The literature reports that a 10% increase in body fat can increase systolic and diastolic blood pressure by an average of 6 mmHg and 4 mmHg. In obesity, abdominal obesity has the highest prevalence of hypertension, and women have a waist circumference of >88 cm. >102cm, the incidence of hypertension is doubled, and IR and sympathetic nerve activity are increased in elderly patients with obesity and hypertension. It is considered to be involved in the pathogenesis of hypertension. Dietary behavior is the primary factor in obesity, and long-term satiety leads to obesity. Increases plasma insulin levels by stimulating the central sympathetic nervous system, accelerating heart rate, increasing cardiac output, and raising blood pressure, which may be an important cause of hypertension in obese people. On the other hand, elderly obese people have kidneys. Increased activity of the renin-angiotensin system, causing an increase in urinary sodium reabsorption, an increase in blood volume, and an increase in blood pressure, in recent years It was found that adipose tissue also exists in the renin-angiotensin system, and angiotensinogen gene expression is increased in visceral adipose tissue, which is positively correlated with BMI and participates in the occurrence of hypertension.
3. Coronary heart disease
Studies have shown that the incidence of obesity in patients with coronary heart disease (CHD) is significantly increased, and obesity has a tendency to increase coronary heart disease. The literature reports that heart failure in elderly obesity, the risk of myocardial infarction is twice that of the general population, some obesity indicators For example, waist/hip ratio (WHR), BMI and waist circumference were positively correlated with CHD mortality. BMI>29 had a 3.3-fold increase in CHD risk compared with BMI<21, and similar risk for Asians even at lower BMI. Sexuality, abnormal distribution of fat in the body, especially the increase of intra-abdominal fat is also associated with CHD. Research surface: waist circumference may be a better predictor than BMI, such as male waist circumference >102cm, female waist circumference >88cm, the risk of CHD is significant Increased, therefore, some scholars believe that obesity is an independent risk factor for CHD, but some studies do not support this view. The Munstex Heax Studg study also found that CHD mortality is related to BMI, and that the effect of overweight and obesity on CHD is achieved by other factors. Postprandial hyperlipidemia is considered to be an independent risk factor for CHD. Older obese people may cause postprandial lipid metabolism abnormalities and CHD if there is a large accumulation of intra-abdominal fat. Biosynthesis-related, 3-adrenergic receptor gene Trp64 A2g mutation is involved in the occurrence of visceral obesity, so the link between obesity and CHD may be due to obesity and other cardiovascular risk factors such as dyslipidemia, hypertension and Due to IR, elevated serum TC levels and hypertension can aggravate coronary atherosclerosis, increased cardiac output in obese people and increase cardiac oxygen consumption. When exercise, oxygen consumption is twice as high as normal weight, so obese Easy to attack labor-type angina pectoris, in addition, elderly obese people blood volume, cardiac output, left ventricular end-diastolic volume, filling pressure are increased, so that cardiac output increased, causing left ventricular hypertrophy, enlargement, myocardial fat deposition caused by myocardial strain , prone to congestive heart failure.
4. Gallbladder disease
Obesity is closely related to the formation of gallstones. Epidemiological investigations show that obesity is a predisposing factor for gallstone development. Obesity increases the incidence of gallstones. First, the total TC and TG in the serum of most obese patients continue to be at a high level. Gallstones form risk factors, and with the occurrence of obesity, the secretion of bile, TC levels increase, and make TC easy to crystallize and precipitate. On the other hand, obese people in the process of weight loss, the TC saturation in bile is further increased, this It may be due to the removal of excess cholesterol in the tissue, so weight loss may also aggravate gallbladder disease. Others who have high-calorie or high-cholesterol foods have increased cholesterol output in the bile, forming gallbladder or bile duct, and TC is supersaturated. .
5. Dyslipidemia
Old age obesity is often accompanied by dyslipidemia. The detection rate of hyperlipidemia is as high as 40%, which is much higher than that of the general population. The dyslipidemia is characterized by plasma triglyceride (TG) and low density lipoprotein cholesterol (LDL-C). Increased, high-density lipoprotein, cholesterol (GDL-C) decreased, this metabolic characteristics are more common in abdominal obesity patients, abdominal fat excess is associated with small and dense LDL particles, BMI and TG levels are positively correlated, and There was a negative correlation with HDL-c. It was reported that BMI>25 had a high TG, and the risk of high cholesterol (TC) and HDL-C decreased by 2 times compared with BMI. Obesity caused by dyslipidemia was mainly due to IR. Therefore, the insulin sensitivity of obese people can be reduced by 5 times compared with normal, and the number of receptors can be reduced by 10 times. In this case, the activity of lipoproteinase is decreased, the activity of LDL receptor is decreased, the HDL is decreased, and the lipoprotein lipase gene is also found. The variant, HindIII gene polymorphism, is associated with elevated triglyceride levels and decreased HDL-C levels in obese patients. Increased plasma leptin levels in obese individuals suggest Leptin resistance. Studies have shown Leptin resistance and lipids. Significant correlation .
6. Obstructive Sleep apnea Syndrome (OSAS), most OSAS found in obese people, studies show that about 60% of obese people with OSAS, severe snoring often accompanied by OSAS, in fact most snorers In the middle of the game, OSAS appeared only after many years of snoring. Obese people have a large amount of fat accumulation in the chest and abdomen, which reduces the compliance of the chest wall, increases the mechanical load of the respiratory system, and reduces the residual capacity of the lung function, while the low lung volume ventilation can make the airway tidal. When the amount of breathing is closed, the lack of lung ventilation during sleep can cause or promote the occurrence of apnea, leading to a decrease in blood O2 partial pressure, an increase in CO2 partial pressure, and a decrease in blood pH, which can cause brain dysfunction, pulmonary hypertension, and high Blood pressure, bradycardia, severe heart failure, respiratory failure, and even sudden death.
7. The incidence of malignant tumors in elderly obese patients is increased. The obese women's endometrial cancer is 2 to 3 times higher than that of normal women. The incidence of postmenopausal breast cancer increases with weight gain, and gallbladder and biliary tract cancer are also common. Obese men The incidence of colon cancer, rectal cancer and prostate cancer is higher than that of non-obese people. Obese people are prone to low back pain and joint pain due to long-term weight bearing.
The determination of obesity in the elderly is mainly based on excessive accumulation and/or abnormal distribution of fat in the body.
Examine
Elderly obesity check
Fasting blood glucose and 2h postprandial blood glucose, glycosylated hemoglobin (GHbA1C), insulin and C peptide, plasma total cholesterol (TC), triglyceride (TG), very low density lipoprotein cholesterol (VLDL-C), blood uric acid can rise High, while high-density lipoprotein cholesterol (HDL-C) can be reduced, 24h urine 17-hydroxycorticosterol and 17-ketosterol emissions are often higher than normal.
The basis for determining obesity in the elderly is to determine the body fat content. The method of measurement involves anthropometry and other physical, chemical, and electronic technologies. The following methods are introduced.
1. Anthropometry The method of measuring such parameters is simple and easy to grasp, but is not suitable for people with particularly developed muscles (such as weightlifters, heavy manual workers) or edema.
(1) Body Mass Index (BMI): This is a standard weight measurement method popular in recent years in the world. It is the international standard for obesity classification recommended by WHO.
The calculation formula is as follows: BMI = actual weight (kg) / height (m2)
In the 1979 WHO distribution, the normal BMI was 18.5-24.9; >25 was overweight; >30.0 was obesity. In 2000, the normal BMI of Asians was 18.5-22.9; >23 was overweight; >25 was obesity.
The body mass index is used to measure the degree of body obesity, which is characterized by less influence on height. The limitation of this method is that it cannot reflect the distribution of local body fat.
(2) Ideal weight and obesity: ideal weight (kg) = height (cm) - 105 or ideal weight (kg) = [height (CM) - 100] × 0.9) (male) or × 0.85 (female), actual The percentage of body weight over ideal body weight is obesity, ie, obesity = (measured body weight - standard body weight) / standard body weight) x 100%, normal: +10%; > 10% to 20% is overweight; > 20% is obesity, The calculation of ideal body weight and obesity has been widely used, but there are certain limitations, such as low accuracy, can not measure local body fat.
(3) Waist Hip Rate (WHR): Although the number of Chinese people with high BMI is small, there are still abnormal fat accumulation and/or fat distribution. WHR is an indicator for distinguishing the type of fat distribution. WHR is high for central obesity, low is peripheral obesity, WHO recommends measuring waist and hip method: waist circumference is the subject taking the standing position, the feet are separated by 25~30cm to make the body weight evenly distributed, at the lower edge of the rib The midpoint level between the upper edge of the frontal bone and the frontal bone is measured at the time of smooth breathing. The hip circumference measures the circumference of the hip (the pelvis). The male WHR>0.90 is the central obesity, and the female WHR>0.85 is the central obesity. The WHO is defined as abdominal obesity (European population) according to the waist circumference of men>94cm and women>80cm. The advantage is that it can reflect the changes of intra-abdominal fat well, but the measurement experience and technique will affect the measurement results.
2. Densitometry is a classical method for measuring body fat composition. Currently, indirect measurement methods are mainly used. The most commonly used methods are horizontal weighing method and skinfold thickness method. Both methods measure the density of the body. Bxoze K's body fat rate calculation formula is used to calculate the body fat percentage, thereby calculating the body weight, fat body weight and body fat. Therefore, it is called the body density method.
(1) Hydrodensitometry Or Underwater Weighing: Underwater measurement is a classic, basic, reliable method for determining the "golden index" of body fat, which is mainly based on Archimedes' The principle of buoyancy divides the human body into two parts: fat mass and fat-free mass. The proportion of fat tissue is low, 0.9g/cm3, and the proportion of non-fat part of the body is 1.1g/cm3. When the human body is weighed underwater, the person who has gained more weight after degreasing has a heavier underwater weight and a higher body density, and the volume and density of the person are obtained according to the following formula, thereby obtaining the body fat content.
Calculation formula: body volume = (land weight - underwater weight) / water density
Body density = land weight / body volume
Body fat percentage = (4.570 / body density - 4.142) × 100%
The advantage of this method is that the result is more accurate, the error is up to 2% to 3% of body fat. The disadvantage is that it takes more time, the instrument used is not convenient to carry, and the cooperation of the tested object is needed, in young children, the elderly and patients. The application in this is very difficult or even impossible, and the amount of local body fat cannot be determined.
(2) Skinful-thickness measurement principle: About 2/3 of the adipose tissue in the human body is distributed under the skin. By measuring the thickness of the skinfold, the total amount of subcutaneous fat and body fat is calculated according to the formula. It is the biceps area, the triceps area, the subscapular area, the abdomen, the waist, etc. The skinfold thickness method is a simple and economical method for measuring body fat because the instrument used is relatively cheap and Portable, has been widely used in clinical and some epidemiological investigations, but the subject's obesity, skin tightness, edema under the skin, skin thickness and the measure of the measurer will affect the measurement results.
3. The principle of Isotopic Dilyeion
Since the fat tissue has almost no moisture, by measuring the amount of water in the body, it is possible to calculate the weight of the body other than fat, and thus the weight of the body fat, by injecting the water of the cesium (hydrogen nuclides) labeled water. Into the human body, after 2 to 4 hours (heavy water is evenly distributed in the body except for the fat tissue), the density of the sputum in the body fluid is measured, and the total amount of water in the body can be calculated, and the fat-removing body weight and body fat content are further obtained.
Fat loss = total water in the body / 0.07 (or 0.72) (this 0.70 or 0.72 is the percentage of human tissue moisture).
Body fat content (%) = [(weight - fat free body weight) / body weight] × 100.
The advantage of this method is that the coefficient of variation of the measured value is small, and the error is about 1%. The disadvantage is that the price is expensive, the technical difficulty is large, the adverse effects of the isotope and the local body fat cannot be measured.
4. Bioelectric Impedance Analysis (BIA) principle
Adipose tissue and other tissues with large water content are different in electrical resistance. The greater the percentage of fat in the human body, the greater the electrical impedance, and the smaller the electrical conductivity, the indirect calculation of the percentage of body fat tissue from the body's conductivity or resistance. Specific method: using a 50 kHz single-frequency or variable-frequency alternating current, a pair of electric plates are placed on the subject's upper and lower limbs to measure the impedance, and the body's moisture content and body fat content are estimated according to the formula.
The advantage of this method is that the price is relatively low, fast and simple, and the repeatability is good. It can be checked at the bedside. The measurement result is very close to the underwater weighing method. It is suitable for epidemiological investigation, but it is reported that the influencing factors of the measurement method are more More, such as body position, body temperature, dehydration, etc., in addition, this method can not measure local body fat.
5. Dual-Energy X-ray Absorptiometry
Two weak X-rays with different energies pass through the human body, and the non-fat tissue, adipose tissue and bone mineral content in the body are calculated indirectly by the difference in X-ray attenuation.
The advantages are safety, convenience, high precision, the disadvantage is that it is expensive, and the weight of the object to be examined is limited. It is suitable for individuals weighing >150kg (300 lbs) and cannot measure local body fat.
6. Principle of ultrasonic testing
The pulsed ultrasound enters the human body, and different tissues have different echogenicity and sound attenuation: in water, the sound attenuation is small; the adipose tissue has less water content, the sound velocity is lower than other tissues, and the echogenic characteristics of adjacent skin muscle tissue are obvious. Differences can be used to distinguish the boundaries of adipose tissue from the sonogram and measure its thickness.
Advantages: non-invasive, inexpensive, reliable, can measure total fat and local body fat, and has a good correlation with CT detection. The disadvantage is that the stability is slightly poor, which is affected by the experience of the examiner.
7. Computed Tomorgaphy (CT) principle
The subject was irradiated with X-rays, and a beam of X-rays scattered around a 1 cm-thick human body was analyzed by a computer to reconstruct the scanned area by attenuation of the X-ray signal, and a series of highly accurate images were obtained, according to the scanning level. Or the adipose tissue area and volume of the segment to estimate the total fat and local body fat, generally using the umbilicus or the 4th to 5th lumbar vertebrae horizontal scanning, the advantage is fast and accurate, measuring the body fat error is less than 1% is the diagnosis of abdominal type One of the most accurate methods of obesity is that it is expensive and has X-ray radiation.
8. Magnetic Resonance Imaging (MRI)
It is a brand-new image inspection technology developed in the 1980s. It has no radioactive damage to the human body. It uses the H protons in the human body to be excited by radio frequency pulses in a strong magnetic field to generate nuclear magnetic resonance. After spatial coding technology, The NMR signal emitted by electromagnetic form is received and converted, and the image is formed by computer. MRI can accurately distinguish the adipose tissue, and calculate the total fat and local body fat according to the area of the adipose tissue on the scanning layer, including multi-layer and single layer (usually adopted Umbilical or 4th to 5th lumbar intervertebral level scans, multi-layer scan is the most accurate method for measuring visceral fat and subcutaneous fat, but it takes a long time for testing and analysis, and it is expensive. The single layer scan predicts the accuracy of body fat. Slightly poor, but greatly reduced test time and inspection costs.
9. Overall electrical conduction
Using fat and moisture to react to electromagnetic fields, estimate the body fat content. Method: The subject is lying flat, passing the electromagnetic field of the 2.5MHz wireless frequency oscillating current generated by the large spiral coil through the human body, and the computer generates the time according to the detector. The coil resistance measured by the phase diagram analyzes the conductivity of the human body and the influence of the electrolyte to derive the body fat content.
The advantage is fast, repeatable (about 2% error), the disadvantage is that it is expensive and can not measure local body fat.
10. Neutron Activation Analgsis
The fat content can be determined at the atomic level. Principle: Rapid bombardment of the subject with known energy, activation of chemical elements in the body, identification of activated chemical elements by emission of x-rays, isotopes with different half-lives, available in two Scanning at different time phases, accurately determining different pheromones, and calculating body fat content.
Features: expensive, difficult to operate, radionuclide radiation is the largest, can not measure local body fat, so this method is rarely used.
11. Infrared induction method (Near Infra redinduction)
Using the principle that infrared rays have good penetrating properties on the skin and its backscattering is linear with fat thickness, infrared non-destructive testing of subcutaneous fat thickness is achieved, such as placing infrared signals on the biceps, measured. The percentage of body fat is highly correlated with the results of other methods.
The method is accurate and has no adverse effects on the human body. The measurement of subcutaneous fat and total fat is superior to the skinfold thickness method. The disadvantage is that the method is complicated and the cost is high.
12. Principle of body potassium determination
Due to the minimal potassium content in the body's adipose tissue, the potassium present in all organs of the human body is radioactively tracked, that is, the body potassium content is estimated by calculating the distribution of the radionuclide 40 potassium or 50 potassium in the body, and the body fat content can be calculated. The disadvantage is that it is expensive, difficult to operate, and cannot measure local body fat.
It can be seen that there is no ideal method for measuring body fat, which is simple, accurate and economical. Therefore, different measurement methods can be selected according to different purposes. The traditional method is underwater weighing, and the skinfold thickness method has been tended to be Bioelectrical impedance method and dual-energy X-ray absorption method, overall electrical conduction, neutron activation method, infrared induction method, body potassium determination method because of special equipment, expensive, complicated methods, difficult operation, etc. Not suitable for routine clinical testing methods, such as the evaluation of total lipids, can be used to determine the above body mass index, ideal body weight, obesity, etc., or by bioelectrical impedance and dual energy X absorption; such as assessment of local body fat or abdomen Type obesity, can measure waist circumference, waist and hip; ultrasound, CT or MRI can be used to determine total fat and local body fat according to actual conditions.
Diagnosis
Diagnosis and diagnosis of obesity in the elderly
Obesity is divided into simple obesity and secondary obesity from the perspective of etiology. Simple obesity is not an endocrine disease, but there are many changes in endocrine hormones. Therefore, there are many similarities with certain endocrine diseases, and differential diagnosis is sometimes difficult. .
Cushing syndrome
Concentric obesity, the degree of obesity is generally not more than moderate, skin purple lines are common, female patients may have small beards, acne and other masculine manifestations, often with vertebral osteoporosis, increased urinary calcium, increased plasma cortisol, and diurnal changes The rhythm disappears, such as an adrenal cortical tumor, the dexamethasone test can not be inhibited.
2. Hypothyroidism (referred to as hypothyroidism or hypothyroidism)
A low weight gain is caused by mucinous edema, not really obese, the patient's expression is apathy, the skin is dry and sweat-free, hair, eyebrows (especially 1/3) fall off, thyroid hormone (T3, T4) levels are lowered, thyroid stimulating hormone ( Elevation of TSH), decreased 131I rate of thyroid absorption, etc. all contribute to the identification of obesity.
3. Hypothalamic syndrome
There are two kinds of nucleus regulating the feeding activity in the hypothalamus: the ventrolateral nucleus is the starvation center, and the ventromedial nucleus is the full center. These two centers are regulated by high-grade nerves, and mental stress and mental stimulation can stimulate the hunger to produce hunger. As a result, eating increases, causing obesity, the hypothalamus itself, such as inflammation, trauma, bleeding, tumors, etc. can invade and destroy the full center, so that the heart loses fullness and eats more, occurs obesity, according to medical history, head CT or MRI and the necessary target gland endocrine tests were identified.
4. Islet B cell tumor (insulinoma)
Often due to repeated hypoglycemia, patients with prevention of hypoglycemia episodes, eating more obesity, can be identified by repeated hypoglycemia, hyperinsulinemia and pancreatic CT or MRI.
5. Water and sodium retention obesity
No obvious endocrine disorders, afternoon limb swelling, early morning relief, can be identified in the vertical position water test.
