Mechanisms of Weight Control By Surgery

Energy balance is linked to the amount of food absorbed and the amount of energy used. The body uses the excess energy that is stored as fat when needed. Body weight is the sum of structural material (muscle and bone), body water and stored fat. Excess fat can be lowered by reducing caloric intake and/or increasing physical activity. Reduction in food intake or absorption and increase in physical activity will cause weight loss.

Energy balance may be changed in two ways by surgery to control obesity:

• Restriction which decrease the intake of food
• Malabsorption which causes some of the food to be poorly digested and incompletely absorbed.

To control weight with an operation that restricts intake the surgeons need to help patients in eating less. This requires a “meal-sized” upper stomach pouch with an initial ½ to 1 ounce (15-30 ml) capacity. The pouch connects to the small intestine through an outlet (stoma), about the size of your little finger. The small pouch and the narrow outlet produce early satiation (a feeling of fullness) that in a compliant patient brings about behavioral changes leading to less caloric intake, and therefore, weight loss.

After adaptation occurs, the average patient can soon eat ½ to more of a cup of well-chewed food without discomfort. Inadequate chewing can result in pain, reflux or vomiting. Patients must eat slowly, reduce meal size and avoid overeating or drinking excessive fluids and carbonated drinks. Failure to abide by guidelines can defeat the purpose of the surgery, by stretching the pouch and/or outlet. Lack of patients compliance is one of the most common reasons for failure.

The simpler and safer restrictive operations do not always produce the weight loss surgeons and patients would like. Therefore, Malabsorption techniques were added to the procedures, some of which include extensive bypass of the small intestine. The risks, complications and side effects generally increase with the alteration of the digestive process. You and your surgeon must balance the risks and benefits over your lifetime with the operation you choose for control of your excess weight. Remember that the greater the operation to produce weight loss, the higher the risks and side-effects.

It is important that you receive adequate information from your surgeon, that you ask questions, understand the answers, be aware of the changes made to the stomach and intestine and know ALL the effects of surgical treatment. The correct path to informed consent is research on your part. Make several trips to the surgeon’s office, consult with more than one physician and talk to other patients who have had similar operations. Attending a support group meeting is an excellent way to learn from patients their experience following surgery. Many sources are available to you to gain the information you need so that you feel comfortable with your choice for weight loss surgery. These sources include the internet, the American Society for Bariatric Surgery and our web-site at the addresses listed. Remember that surgery is not the cure for obesity and only well-informed, compliant patients make these operations succeed.