Obesity and its relationship with endocrine metabolism, mental health, and diagnostic criteria

Obesity profoundly alters the body's endocrine and metabolic balance. Obese individuals commonly exhibit hyperinsulinemia, and plasma insulin levels are directly proportional to the severity of obesity. This hyperinsulinemia inhibits the pituitary gland's secretion of growth hormone because it promotes the synthesis of somatostatin in the liver. Furthermore, obesity easily leads to hormonal imbalances, particularly in women. The sustained increase in estrogen levels inhibits the normal secretion of follicle-stimulating hormone (FSH) and luteinizing hormone (LH), resulting in ovulation disorders, menstrual irregularities, and even infertility.

Among metabolic diseases, obesity has the most direct relationship with type 2 diabetes. Studies have found that the relative risk of developing diabetes in obese individuals is 7.28 times higher than in those of normal weight (95% CI: 6.47–8.28). The prevalence of diabetes increases stepwise with increasing BMI: 15% in the overweight group, 23% in the grade I obesity group, 33% in the grade II obesity group, and as high as 43% in the grade III obesity group. In predicting the occurrence of diabetes, waist-to-hip ratio (WHR) is slightly more effective than BMI and waist circumference. Childhood obesity-induced metabolic disorders also warrant attention, as it can induce metabolic syndrome, hypothalamic syndrome, and polycystic ovary syndrome, severely impairing growth and development.

Mental health is another major concern in obesity management. Obese individuals are prone to social exclusion and ridicule, living under a long-term psychological shadow. Studies show that mental health symptoms are related to obesity and abdominal fat distribution in women. Among middle-aged men, waist-to-hip ratio (WHR) is closely associated with depression, anxiety, and sleep disorders, and the more severe the depressive symptoms, the more significant the increase in an individual's WHR. For children and adolescents, obesity is often accompanied by feelings of inferiority, withdrawal, and dependency; obese boys aged 4 to 9 are four times more likely to experience depression than children of normal weight. Girls are more likely to experience negative emotions, interpersonal conflicts, and low self-esteem due to being overweight.

For scientific intervention, precise evaluation criteria must be used in clinical practice. The most commonly used indicator is Body Mass Index (BMI), calculated as: BMI = weight (kg) / height (m)². According to the health industry standard "Adult Weight Determination" (WS/T 428-2013), the weight classification for Chinese adults is as follows: BMI < 18.5 is underweight; 18.5 ≤ BMI < 24.0 is normal weight; 24.0 ≤ BMI < 28.0 is overweight; and BMI ≥ 28.0 is obese. BMI can effectively reflect the degree of obesity, but it should be noted that individuals with well-developed muscles may be overweight, while older adults with muscle loss may be underweight.

Waist circumference (WC) is the simplest and most practical indicator for measuring abdominal fat accumulation (central obesity). The World Health Organization defines obesity in the Asia-Pacific region as a waist circumference ≥ 90cm for men and ≥ 80cm for women. A waist-to-hip ratio (WHR) > 0.9 for men and > 0.85 for women is diagnosed as central obesity (visceral obesity). While the ideal weight estimation method is crude, it is widely used in clinical practice. A simplified calculation method is: Ideal weight (kg) = Height (cm) - 105. An overweight percentage exceeding 20%–30% is considered mild obesity, 30%–50% is moderate obesity, and over 50% is severe obesity.

Body fat percentage criteria can identify "normal-weight obesity." The Asia-Pacific region's criteria are: men > 25%, women > 33%. The essential body fat standard for adults is 3%–8% for men and 12%–14% for women; the healthy body fat standard is 15%–20% for men and 25%–30% for women. In conclusion, a complete obesity diagnostic system can only be constructed by combining physiological indicators, psychological assessments, and physical measurements, providing a basis for subsequent interventions.