Chapter 27 OBESITY SURGERY
DEFINITIONS OF OBESITY
The increasing prevalence of obesity is a worldwide phenomenon and it is a disease with protean adverse physical, social and psychological effects. The classification of obesity defines the relationship between a person’s height and weight, the body mass index (BMI) to stratify patients according to their risk of obesity-related medical conditions (Table 27.1).
TABLE 27.1 Obesity definitions*
| BMI (kg/m2) | Obesity class | |
|---|---|---|
| Underweight | <18.5 | – |
| Normal | 18.5–24.9 | – |
| Overweight | 25.0–29.9 | – |
| Obesity | 30.0–34.9 | I |
| 35.0–39.9 | II | |
| Extreme obesity | 40.0+ | III |
* The term ‘morbid obesity’ relates to BMI 35.0–39.9 with medical comorbidities or BMI 40 and above.
TREATMENT OF OBESITY
Having surgery entails taking on some risks, so it is obvious that this is not a treatment that can be applied liberally. The effects of any operation, both positive and negative, may be permanent and some complications may develop insidiously many years later and, therefore, may not be related to the operation. Current, generally accepted criteria for selecting patients for surgery are listed in Table 27.2.
TABLE 27.2 Selection criteria for bariatric surgery
| Body weight | BMI >40 |
| BMI 35–39.9 with medical comorbidities | |
| No endocrine cause | |
| Resistant obesity | Obesity present >5 years |
| Multiple failed non-surgical attempts | |
| Psychological profile | No alcohol or drug use |
| No or controlled psychiatric conditions | |
| Understanding of surgery and commitment to follow-up |
Weight-loss surgery
Obesity is a chronic, probably life-long disease and, therefore, the current surgical solutions are designed to cause permanent alterations to gastrointestinal physiology. These physiological alterations, while necessary for the maintenance of weight-loss, may become disordered and lead to the patient presenting for medical or surgical care. There are a range of bariatric surgical procedures currently undertaken, and a number of historical procedures that remain of interest due to the large number of patients who have undergone them in the past. Thankfully there is sufficient homology between all of the historic and current procedures to allow them to be grouped into categories when discussing them. Complications following surgery may be related to weight loss itself (e.g. gallstones), anatomic changes (e.g. vomiting, obstruction) or altered nutritional status (e.g. decreased intake, decreased absorption or gastrointestinal losses). Most of the subtle nutritional complications that can arise after this type of surgery are beyond the scope of this chapter and will not be discussed.
BARIATRIC OPERATIONS
Operations for morbid obesity are grouped into:
These terms are historically based and fail to take into account the often complex variations between individual operations; they also inadequately explain the mechanisms by which the procedures work.
