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Gastric Bypass Surgery How it Works

The Roux-en-Y gastric bypass, most simply known as gastric bypass, is the most popular type of weight loss surgery. 90% of patients who undergo this procedure lose over 50% of their excess body weight. After two years, total weight loss equals approximately 70% of excess body weight.

Gastric bypass uses all four surgical mechanisms in the following ways:

  • Restriction is accomplished by creating a pouch approximately the size of an egg. This decreases the size of the stomach by 90%; you’ll feel full after only a few bites.
  • Malabsorption occurs because a segment of the small intestine is bypassed, or skipped over. After food empties from the pouch, it is not digested and absorbed by the body until it mixes with the digestive enzymes much lower in the intestinal tract. This means your body absorbs less calories.
  • Hormonal changes occur when the stomach is divided and the intestines are re-routed. This results in reduced feelings of hunger – 90% of patients report that they are “just not hungry” after the procedure. This is a lasting and very useful effect.
  • Dumping syndrome is likely to occur when carbohydrate-heavy meals are consumed. Because your food enters directly into the intestines instead of being diluted and broken down in the stomach, you may experience cramping, nausea, vomiting, sweating or diarrhea when eating overly-rich meals. As a result, you likely won’t even want to eat sweets or other dishes that used to tempt you.



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Benefits of Gastric Bypass Life After Weight Loss Surgery

FMC Bariatric patient on roller coaster

Bariatric surgery can give you the opportunity to live a longer, happier life.

When accompanied by healthy habits – like smart diet choices and regular exercise – long-term, successful weight loss is seen in approximately 80% of gastric bypass patients.

After weight loss, patients often experience a drastically improved quality of life, and proudly report that they are now able to do things they could have only dreamed of before, including shopping freely at the mall, playing with their children, mowing the lawn and riding roller coasters at the amusement park. Think about it: what are you looking forward to doing?

Additionally, almost all patients experience an amazing improvement in overall health. In many cases, diseases and conditions associated with obesity – like diabetes, joint pain and sleep apnea – resolve after surgery.

Calculating Results


You’ll often hear the success of a weight loss surgery measured in terms of percentage of excess weight loss (% EWL). In most cases, a surgery is considered successful if it resulted in at least 50% excess weight loss.

If you’d like to keep track of your % EWL at home, the formula is: % EWL = weight lost ÷ excess body weight × 100

For example, suppose an individual is 5’6″ tall and weighs 250 lbs. At this height, an ideal body weight is 150 lbs. This means they have 100 lbs. of excess body weight. If they lose 50 lbs., then their % EWL is:

% EWL = 50 lbs. (weight lost) ÷ 100 lbs. (excess body weight) × 100%
% EWL = 0.5 × 100%
% EWL = 50%



“I feel like I’ve been given my life back.”

 Millie Pritchard, Bariatric Surgery Patient

Learn more about Millie’s story here

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Let us know how we can help you take the next steps toward better health and wellness for yourself or a family member. If you have additional questions, please call our office at 740-475-0442.