Multiple methods for diagnosing obesity and the root causes of obesity
(2) Body Mass Index method: Body Mass Index, also known as Body Mass Index, is commonly referred to as BMI index internationally. The formula is: Body Mass Index = weight (kg) / height (m)².
Body Mass Index (BMI) can be easily calculated given height and weight, making it suitable for everyday use. The BMI method is suitable for adults. Currently, there is no unified standard for defining obesity, either internationally or domestically. In my country, some advocate a BMI ≥24 as the standard for judging obesity, while others advocate ≥25, and still others propose ≥24 for men and ≥26 for women. Based on extensive survey data, the author believes that using a BMI ≥24 as the standard for judging obesity for both men and women is more reasonable.
(3) Body Density Method: Archimedes ingeniously measured the gold content in a gold crown, thus establishing the famous Archimedes' Principle. Human anthropometric researchers have used this principle to calculate the body fat content. This method has become the "gold standard" for determining body fat content and is one of the most scientific methods for diagnosing obesity. However, because it requires complex instruments and a laboratory with specific conditions, and the subject must be submerged underwater, this method is difficult to widely apply.
(4) Total Water Content Method: It is generally believed that adipose tissue contains no water, while lean body tissue contains 73% water. Therefore, the lean body tissue content can be calculated based on the total water content. Lean body tissue (kg) = total water (L) / 0.73, body fat mass (kg) = body weight (kg) - lean body tissue weight (kg), body fat percentage = body fat mass (kg) / body weight (kg) × 100%. Obesity can be determined based on the body fat percentage.
(5) Skinfold Thickness Method: Subcutaneous fat accounts for about 2/3 of human body fat, and its thickness is parallel to the overall degree of obesity. Therefore, measuring subcutaneous fat thickness can roughly reflect the amount of body fat, and obesity can be judged based on the fat content. The skinfold thickness meter used to measure skinfold thickness is a specially designed curved-leg pliers. This method is simple, but its repeatability is poor.
(6) Bioelectrical Impedance Method: The bioelectrical impedance method is a new method for measuring body composition that has been successfully developed in recent years. This method utilizes the principle that adipose tissue has weaker conductivity than lean tissue, and infers body fat content by measuring the body's electrical impedance. The bioelectrical impedance method is simple, fast, safe, and highly accurate.
3. Grading of obesity
Understanding the different levels of obesity is essential for effective weight loss. For example, the dietary weight loss method introduced in this book determines the daily calorie reduction based on the degree of obesity and develops a dietary plan accordingly.
(1) Determining the degree of obesity in obese individuals using the standard weight method: Obesity degree (%) = [Actual weight (kg) - Standard weight (kg)] ÷ Standard weight (kg) × 100%. An obesity degree within ±10% is considered normal weight, or standard weight; 10%–20% is overweight; 20%–30% is mild obesity; 30%–50% is moderate obesity; and over 50% is severe obesity. Individuals with an obesity degree exceeding 20% should lose weight.
(2) Judging obesity by body fat percentage: As mentioned earlier, body fat percentage is the most accurate and scientific method for judging obesity. Currently, there are not many units in China that use body fat percentage to judge obesity, so there is no standard for judging obesity based on body fat percentage. Based on the results of large-scale population surveys and referring to relevant foreign data, the author believes that a body fat percentage of less than 5% is considered mild obesity; a body fat percentage of 5% to 10% is considered moderate obesity; and a body fat percentage of more than 10% is considered severe obesity. For example, if the standard body fat percentage is 25%, and the measured body fat percentage is 25.1% to 30.0%, then the person is mildly obese; 30.1% to 35.0% is moderately obese; and above 35.1% is severely obese.
**(II) Causes of Obesity**
1. Excessive calorie intake
All human activities require energy, which comes from energy-producing nutrients, including carbohydrates, fats, and proteins. After food containing these nutrients is digested and absorbed, it undergoes a series of oxidative breakdowns catalyzed by enzymes, gradually releasing energy from the three major nutrients to meet different physiological needs. Any excess energy is converted into fat and stored. Excessive fat accumulation in the body leads to obesity. The main reasons for excessive energy intake are as follows.
(1) Overeating: In a large-scale population survey, the author found that obese people have very good appetites and seem to have a special affection for food. They have a strong desire to eat when they see food, and their food intake is significantly more than that of ordinary people. They also eat faster than ordinary people. Eating quickly also promotes the intake of too much food. Generally, it takes 15 to 20 minutes after a meal for the brain's feeding center to send a signal to stop eating. Overeating people have already consumed a lot of food before the feeding center sends the signal to stop eating, and their energy intake significantly exceeds the body's needs. People who frequently attend banquets and parties also consume too much energy, which is why there are more obese people among them.
(2) Snacks: Obesity caused by a fondness for snacks is common among children and young women. Currently, my country offers a vast variety and quantity of snacks and fast food, most of which are quite appealing in terms of packaging and taste, leading to a significant number of people enjoying snacks. However, from a nutritional perspective, snacking is detrimental to health. Fast food is mostly high in fat and salt, and low in fiber, with 40% of its energy coming from fat and very little fiber. Canned fruits and beverages contain large amounts of sucrose, with some canned goods reaching or exceeding saturation levels. Various pastries and certain finely processed nut snacks also provide the body with large amounts of fat and sugar. Popular children's foods such as chocolate and ice cream also have considerable calorie content. Therefore, these foods are all fattening.
(3) Picky eating: Obese people's picky eating is usually habitual. These people mainly prefer sweets and high-fat foods that taste delicious. Sugar and fat are both heat-generating nutrients, and fat is the nutrient that generates the most heat. Therefore, the result of picky eating is that the body will ingest a lot of energy from the diet, causing weight gain. Middle-aged and elderly people who especially like high-fat diets (fried, deep-fried, and braised foods) are more likely to gain weight if they do not consciously control their dietary fat and change their bad eating habits of liking greasy and rich foods, as their basal metabolism and activity decrease with age.
(4) Alcohol Consumption: Some people believe that alcohol consumption is unrelated to obesity, but in fact, many cases of obesity in adult men are caused by alcohol consumption. Alcohol is a substance with a high energy production rate, with each gram of alcohol producing 29 kilojoules (7 kilocalories), second only to fat. Alcohol can only provide energy to the body and has no other nutritional effects. Although beer contains very little alcohol, generally between 3% and 5%, regular beer consumption can lead to weight gain, hence the term "beer belly." Beer has a high energy production rate; 1 liter of 12-degree beer can produce 2092 kilojoules (500 kilocalories) of energy, earning it the nickname "liquid bread." At the same time, the hops in beer can stimulate the gastric mucosa, promote appetite, and increase food intake. Therefore, regular beer consumption can easily lead to weight gain.
2. Reduced heat energy consumption
A person's body can only maintain a normal fat content when energy intake and expenditure are equal. If energy intake is not more than average, but energy expenditure is reduced, a relative energy surplus can occur, leading to fat accumulation and obesity. The main reasons for reduced energy expenditure are as follows:
(1) Reduced physical activity: With social development, mechanized production has freed people from heavy physical labor, greatly reducing the time and intensity of physical labor. In addition, the number of people engaged in light physical and mental labor is gradually increasing, and their energy consumption is significantly lower than that of those engaged in moderate and heavy physical labor. Therefore, less physical activity is the main reason for obesity in this group of people.
(2) Excessive sleep: The body consumes very little energy during sleep. If you sleep for a long time, energy consumption will inevitably decrease, and the excess energy can only be stored as fat in the body. Excessive sleep often leads to obesity, and obese people are more likely to oversleep. This creates a vicious cycle, making people even fatter. Therefore, excessive sleep is an important factor causing obesity.
(3) Age-related changes: The amount of energy a person consumes to maintain life changes with age. After 16-17 years of age, due to the cessation of growth, the amount of energy consumed to maintain life gradually decreases. The rate of decline accelerates around age 40, and by age 70, it has decreased by 30%. After middle age, physical activity gradually decreases, and energy consumption also decreases accordingly. If this is not adjusted in time, obesity may occur. This is why some people gain significant weight after age 30.