How Does Weight Loss Surgery Work?

Obesity rates have almost tripled in the last 30 years, according to the National Health and Nutrition Examination Survey. Given its high and widespread prevalence and its association with chronic diseases, such as diabetes, heart disease and cancer, obesity is now a global concern.

Obesity is defined as having a Body Mass Index (BMI) greater than 30. BMI is a crude population measure of obesity defined as the ratio of one’s body weight (in kilograms) over the square of one’s height (in meters).

What causes obesity in the first place? At the root of obesity is a positive energy surplus. Put it simply, weight gain is the result of consistently giving your body more calories than it burns. Conversely, weight loss occurs when the body expends more energy than it receives, a situation known as caloric deficit or negative energy balance.

How Does Weight Loss Surgery Work?

A negative energy balance can be achieved in two ways. One way is eating less food. The other way is absorbing less food. In general, bariatric surgeries work both ways. They lead to weight loss because they limit the amount of food you can eat (restriction) while at the same time they lower the capacity of your digestive system to absorb food (malabsorption).

How Does Bariatric Surgery Compare to Conventional Weight Loss Programs?

Morbid obesity is currently treated with pharmacological agents (i.e, orlistat, sibutramine), low-calorie diets (i.e, Atkins, Weight Watchers, Medifast, Nutrisystem), behavioral modification, exercise and surgery. What separates weight loss surgery from the other weight management strategies is that surgical procedures bring about significant and sustained weight loss.

As Dr. Tice explains in his study published in the American Journal of Medicine, dietary treatments and medication therapies produce a long-term weight loss of only 4-7 kg. Bariatric surgery, on the other hand, consistently brings about 40kg weight loss and eliminates diabetes, hypertension and obstructive sleep apnea—common obesity comorbidities.

While bariatric surgery is proven to greatly improve obese people’s health, it should be the last resort when conventional weight loss programs have failed.

General Overview of Weight Loss Surgeries

Bariatric surgeries are of two types; those that are purely restrictive and those that are both restrictive and malabsorptive. Purely malabsorptive procedures are not performed due to high risk of complications.

Restriction.Restrictive procedures reduce the size of the stomach limiting the amount of food that can be ingested. They do not interfere with the process of food digestion and absorption. Normally, the stomach’s capacity is 6 cups. After surgery, the size of the stomach becomes less than a cup. Patients cannot eat large amounts of food. If they eat more than 1 cup of food, they feel nauseous. Less food in the stomach leads to weight loss.

Today, the most commonly performed restrictive procedures are Gastric Band and Sleeve Gastrectomy.

Malabsoption. Malabsorptive bariatric surgery bypasses a portion of your small intestine limiting the amount of nutrients that you can absorb. The fewer calories you can absorb the more weight you will lose. Normally, the small intestine connects the stomach to the colon, measuring about 22 feet long. After surgery, food skips the greatest part of the small intestine. It goes directly from the stomach to the last section of the small bowel and runs through its last 3-5 feet before it meets the colon.

Today, the most commonly performed restrictive/malabsorptive procedures are Gatric Bypass and Biliopancreatic Diversion with Duodenal Switch.

About the author
These series of articles on weight loss surgery are written by Matthew Denos, PhD, a biology scientist who researches and writes about current weight management strategies. He also makes available discounted Medifast shakes and a Nutrisystem coupon code, two medically studied meal replacement weight loss programs.

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