Gastric Bypass Weight Loss

Published Studies

There have been 100s of studies published by 100s of surgeons on gastric bypass weight loss, and the results are highly variable. Some surgeons report average gastric bypass weight loss to be as low as 50-55% EWL (EWL – excess weight loss, definition below), and some report average weight loss to be as high as 75-80% EWL.*

This is a wide range – the difference between 50% EWL and 80% EWL is 30+ pounds for the average patient (100 pounds overweight), and more for higher BMI patients. The main reason for this variability is the fact that different surgeons do the gastric bypass operation in different ways, and these differences affect patient outcomes.*

Studies typically show that gastric bypass patients, on average, regain some weight long-term. The few good long-term studies that have been published report that gastric bypass patients maintain an average of 55-60% EWL at 10+ years after surgery.*

Industry Average

Studies report that different surgeons achieve different average weight loss outcomes (50-80% EWL) after gastric bypass surgery, but what is the overall industry average weight loss for all gastric bypass surgeons? A 2014 study by Livingston et al helps to answer this question. Livingston et al compiled data from 11 high-quality gastric bypass studies including 3,544 patients. From this data the overall average weight loss at 2 years after gastric bypass was 66.5% EWL.*

The long-term industry average weight loss is harder to figure out. The few good published long-term studies (reference, reference, reference) report weight loss to be 55-60% EWL at 10 years after gastric bypass, with an overall average of 57% EWL.*

Dr. Oliak’s Gastric Bypass Weight Loss Statistics

Orange County gastric bypass surgeon Dr. Oliak’s gastric bypass weight loss statistics are better than the industry averages. Dr. Oliak’s gastric bypass patients average 78% EWL at 2 years after surgery, and 66% EWL at 10-13 years after surgery.*

* The weight loss statistics quoted on this page are averages. Individual patient results vary. Some patients lose more weight than the average, and some lose less.

Gastric Bypass Surgeon Dr. Oliak’s Weight Loss Statistics

76% EWL after 1 year

78% EWL after 2 years

75% EWL after 3 years

72% EWL after 5 years

74% EWL after 7 years

66% EWL after 10-13 years

Gastric Bypass Surgeon Dr. Oliak’s Weight Loss Statistics Compared to Industry Average

Time after surgery

Dr. Oliak’s %EWL*

Industry average %EWL*

2 years



10 years



* Orange County gastric bypass surgeon Dr. Oliak’s %EWL (excess weight loss) statistics are for all gastric gastric bypass operations (>1000) completed 2002-2015. Industry average %EWL statistics are calculated from the published studies quoted in the text above. Disclaimer – the gastric bypass weight loss results above are averages. Individual patients can lose more or less weight than the average.

What is excess weight?

Excess weight is the amount of weight over ideal weight. Ideal weight can be found in Metropolitan Life Insurance height-weight tables. Ideal weight is considered to be the middle weight in the medium frame size range. For example, ideal weight (not goal weight) for a 5’4″ woman is considered to be 134 pounds, and ideal weight (not goal weight) for a 5’11” man is considered to be 164 pounds.

Gastric Bypass Complications

Gastric bypass is considered to be a safe operation. As with all operation, however, complications can occur. Potential complications can be categorized as early (within 30 days of surgery) or late (>30 days after surgery). The most important early complications are leaks and blood clots, and the most important late complications are vitamin/mineral deficiencies, bowel obstructions, ulcers, and alcohol abuse.

Gastric Bypass Leak

The most feared early complication that can occur after gastric bypass is a leak from the stomach or intestine. This is a potentially life-threatening complication that all surgeons try hard to prevent.

Published Studies

Published gastric bypass outcomes studies report leak rates after gastric bypass to vary over a wide range, from 0-8%.** Because leaks occur from the surgical line of division on the stomach or intestine, the risk for a leak is determined largely by the details of how the operation is performed. The reported range of 0-8% is large, and underscores the fact that quality of surgery varies widely between surgeons.

Industry Average

The leak rate after gastric bypass varies widely between surgeons (0-8%), but what is the overall industry average leak rate for all surgeons? A recent 2014 study by Zellmer et al answers this question. Zellmer et al reviewed 28 gastric bypass leak studies including 10,906 patients, and found the overall average leak rate to be 1.9%.**

Dr. Oliak’s Gastric Bypass Leak Statistics

Orange County gastric bypass surgeon Dr. Oliak’s leak rate for gastric bypass operations (>1000 operations performed 2002-2015) is 0%. This ranks among the best reported leak rate statistics in the field, and is significantly lower than the industry average.**

** Leaks can occur after gastric bypass surgery. A surgeon’s leak rate in the future may be different that his/her leak rate in the past. Dr. Oliak’s 0% leak rate statistic applies to primary (non-revision) laparoscopic gastric bypass operations (>1000 since 2002), and conversion operations of LAP-BAND® to gastric bypass.

Late Complications

There is the potential for complications to develop long-term after gastric bypass surgery. Regular long-term follow-up is important after gastric bypass surgery to screen for potential complications. When complications develop, it is important that they get diagnosed and treated early rather than late. Potential long-term complications include vitamin/mineral deficiencies (common), bowel obstructions (2-3%), ulcers (5%), and alcohol abuse.

Gastric Bypass Improves Medical Conditions

Medical problems associated with weight, including diabetes, high blood pressure, hyperlipidemia, sleep apnea, joint pain, asthma, depression, infertility, urinary stress incontinence, lower extremity swelling, and headaches all tend to resolve or improve with weight loss after gastric bypass surgery.*

Diabetes – Gastric bypass induces remission (normal blood sugar without medication) of diabetes in about 80% of patients (reference). Patients typically can discontinue their diabetes medications immediately after surgery.*

Gastric Bypass Patients Live Longer

Numerous published studies have shown that weight loss surgery patients live longer than similarly obese patients who don’t have surgery. The reason for this is that the surgery patients lose weight, become healthier, and suffer fewer heart attacks, fewer strokes, and less cancer (reference).*

  • 0% leak rate**
  • 76% excess weight loss 1 year after bypass*
  • 66% excess weight loss 10-13 years after bypass*

Gastric Bypass before & after

See more
  • Tami
  • Procedure:Gastric Bypass
  • Weight Lost: 75 lbs
  • Excess Weight Lost: 85%
  • Disclaimer: Individual results vary
I had gastric bypass 8 years ago with Dr. Oliak and I would do it again tomorrow. It was the…
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