Physiological Section Continued: Classification of Obesity Body Types, Predisposing Groups to Weight Gain, and Genetic Factors

Obesity appearance classification

Pears and Apples

Apples and pears are common fruits, and their shapes have been used as metaphors for different types of obesity. Because pears (European pears) are small in the upper body and large in the lower body, people who are not fat in the upper body but are fat in the lower body are called "pear-shaped." Apples, on the other hand, are the opposite; people who are fat in the upper body but not in the lower body are called "apple-shaped."

Of course, this is just a rough classification. Many people are thin in both the upper and lower body, or slightly overweight in both, which falls somewhere in between. In epidemiological studies, it is worth mentioning that people who are obese in the lower body are less likely to have cardiovascular complications. Many European women have quite large hips and thighs, but they are safer than people of the same weight who are obese in the upper body.

Upper body obesity is usually characterized by a waist circumference significantly larger than the hip circumference, with more fat around the waist. It is often accompanied by higher rates of high blood pressure and high cholesterol, making cardiovascular problems more likely. This condition is more common in men, so if a man's belt hole shifts outwards, he should be concerned and consult a specialist for a checkup.

Who are prone to weight gain?

From an age perspective, the obese population increases with age. But how can one plan ahead and anticipate future weight gain while young? Here are a few points for reference:

1. Both parents are obese.

2. Those who have given birth to a giant baby or who are themselves macrosomic infants (birth weight greater than 4000 grams).

3. Parents with low socioeconomic status or who do not value children's nutritional knowledge.

4. Parents have multiple lifestyle-related diseases such as hypertension, hyperlipidemia, hyperuricemia, diabetes, and cardiovascular disease.

5. People who like to eat junk food (foods that are high in calories and low in nutrients).

6. People who dislike exercise.

The danger of the above six points decreases in that order, but the more points a person has, the easier it is for them to gain weight.

Why do I gain weight?

Obesity can be divided into two main categories: primary and secondary. Primary obesity is caused by environmental factors such as overeating and lack of exercise, and the cause cannot be detected with current hospital equipment. Secondary obesity, on the other hand, has a clear cause that can be found. Common causes include myxedema due to hypothyroidism, Cushing's syndrome due to hypersecretion of adrenal cortex hormones, endocrine disorders such as islet cell tumors of the pancreas, as well as decreased menstruation in women, or polycystic ovary syndrome with a tendency to develop masculinization and hirsutism.

These secondary forms of obesity are still in the minority; most people's weight gain is primary, primarily caused by overeating. The body's energy requirements are related to its basal metabolic rate and the energy consumed through exercise; if dietary energy exceeds the body's energy needs, weight gain will occur.

Most people gain weight gradually after adulthood. In addition to reduced physical activity and increased food intake, the decrease in basal metabolic rate as people age is also a contributing factor.

Heredity

Due to blood ties and shared living habits within a family, many diseases often occur within the same family. This phenomenon of parents and children sharing the same disease due to blood ties is called "hereditary disease" in traditional Chinese medicine. Is obesity hereditary? The most famous example is the Danish twin study. When twins are photographed from behind, two main categories can be identified: one group has similar back shapes and degrees of obesity; the other group has different back shapes and degrees of obesity.

The former refers to twins formed from the same fertilized egg, while the latter refers to twins formed from different fertilized eggs. This illustrates that identical twins, having identical innate factors (genes), are more likely to exhibit similar body shapes and obesity levels. In contrast, fraternal twins, although born at the same time, exhibit less similar body shapes and obesity levels due to their different innate factors.

American research shows that if a single parent is obese, their children have a 50% chance of being obese, while if both parents are obese, the chance is as high as 80%. Conversely, 70% of obese children's parents are also obese. In the long-term stable and industrialized United States, this is because there are not much difference in lifestyle, resulting in similar parent-child environmental factors.

In contrast, Taiwan's environmental factors have changed drastically due to rapid industrialization, automation, and urbanization. For example, children now lack outdoor play spaces, and television and electronic toys have become important forms of entertainment. The spread of high-calorie foods has resulted in a higher obesity rate among this generation of children compared to the previous generation of adults. Therefore, in our weight loss clinic, only 20% of obese children are obese in both sexes, while 50% of their siblings are also obese. Thus, to study obesity, we must first understand Taiwan's unique local environmental factors.