What is Obesity?

Dr. WONG Kin Wa

Resident Medical Officer

Specialist in Emergency Medicine

One of the hottest topics in our beauty-and health-conscious world is weight control or weight reduction. While almost everyone strives to be slim according to his or her own standard, there exists an objective definition of obesity in medical field.

Overweight and obesity are currently defined by the World Health Organisation (“WHO”) as excessive fat accumulation that presents a risk to health. Many chronic conditions are closely associated with obesity, such as diabetes, hypertension, cardio-and neurovascular diseases, cancers, degenerative arthritis, sleep apnea, renal disorders, fatty liver, liver cirrhosis, etc. Research also shows that obese patients are three times more likely to suffer from diabetes, metabolic syndrome and dyslipidemia than people with normal weight.

According to the WHO’s Global Burden of Disease Study 2017, while over four million people die from overweight or obesity each year, a 5% weight loss can improve hypertension, diabetes and other obesity-associated diseases. A growing trend was also revealed in the Hong Kong Population Survey 2017: almost half of the population aged from 15 to 84 was overweight or obese, with up to 30% and 5.3% suffering from obesity and severe obesity respectively. All these results point to a fact that, more than about appearance, obesity is a health issue with grave implications. 

Diagnosis of Obesity

Being the commonest method for diagnosing obesity, the Body Mass Index (“BMI”) is calculated by dividing a person’s weight (kg) by the square of height (m²). For Hong Kong Chinese adults, a BMI of over 23 is considered overweight, while over 25 is obese.   

Both the total fat content and fat distribution are closely related to health. Excessive calories are converted into fat which will firstly be stored underneath the skin, then inside the abdomen. Accumulation of subcutaneous fat leads to increase in body weight, while excessive fat in the abdomen is the culprit of central obesity and its related health risks. Waist circumference is an indicator of central obesity. To reduce the risk of central obesity, it is recommended that waist circumference should be less than 35.5 inches for male and less than 31.5 inches for female.

Weight Management: Be Proper, Comprehensive and Effective

A multifaceted approach is required to achieve weight control and promote weight loss, ranging from diet control, moderate exercise to lifestyle modifications. Patients with severe obesity or obesity-associated complications may need further treatments based on individual condition, such as pharmacological treatment or even surgery.

Common Misconceptions about Obesity

1. Can I lose weight by dieting？

We get energy from the food we eat every day, and excess energy is stored as fat in the body. The key to weight control is a balance between energy intake and output. 

To prevent fat accumulation, you need to create a negative “energy balance” by reducing calorie intake and increasing physical activity. With extreme dieting, the calories intake may become too low to meet the basal metabolic need and maintain the body’s basic functions, leading to easy fatigue, muscle loss and slower metabolic rate thus calorie consumption. Instead of losing weight, you may even gain weight while eating less.

2. Can I lose weight faster with more strenuous exercise?

Research shows that the optimal heart rate for fat burning is 70% of the maximum heart rate. Exceeding this heart rate, you will be able to train your cardiopulmonary function, but you cannot burn fat efficiently.

Similarly, prolonged aerobic exercise may dampen the effect of weight reduction. Better keep it no longer than 45 minutes, otherwise fat burning will become less effective as our body starts to breakdown muscles to provide more energy. Energy consumption will decline when muscle mass reduces.

3. Can slimming products promote weight loss?

Most slimming products are non-registered medications. As they are not subjected to scrutiny by the authorities, their safety and efficacy are in doubt. Severe side effects may also occur after use. According to the research by the Department of Health, some slimming products were found to contain undeclared and banned drug ingredients, such as sibutramine (banned for increased cardiovascular risk), animal thyroid tissue and diuretics.  

Although animal thyroid tissue may lead to gradual weight loss by increasing metabolic rate and energy consumption, side effects such as arrhythmia and heart failure may occur. Long-term use may also lead to symptoms of hyperthyroidism such as palpitations, tremor, irritability, heat intolerance, insomnia, irregular menstrual period, etc. On the other hand, one can quickly lose weight with diuretics. But the weight reduction was, in fact, due to water loss. Their body fat content remains unchanged. Severe complications, such as low blood pressure, irregular heartbeats, renal damage and even coma may occur when water and electrolytes loss are excessive.

Currently, there are three types of weight reduction drugs registered in Hong Kong. They have different mechanisms of action, i.e. lowering appetite or reducing fat absorption and decomposition. The latest one promotes weight loss by enhancing fullness sensation and reducing hunger. Each drug type has its own benefits and side effects. They shall not be taken without doctor’s prescription.

4. Can liposuction achieve weight loss?

Contrary to most people’s belief, liposuction is not an ideal method for weight loss. Liposuction only removes fat from specific areas of the body. Its main purpose is to improve body shape. It cannot achieve genuine fat and weight reduction. Without diet control and appropriate lifestyle modifications, fat will later re-accumulate in the liposuction treated areas.

For patients with morbid obesity or obesity-related complications, the advanced development in bariatric surgery can provide them with an effective and long-standing solution to their physical and mental problems. These weight reduction surgeries are also proven to be effective in preventing premature deaths. Please consult your surgeon for details.

Conclusion

Obesity is not just about appearance – it also presents a severe risk to health. Effective and sustained weight control can help preventing chronic diseases. All you need to win this lifelong battle are expert supports from multidisciplinary medical professionals and a strong commitment to achieve ideal weight and good health.