The attempt to reverse the bypass to normal anatomy can cause rare but serious complications. The parts of the stomach and small intestine can be put together again but their function will never be quite the same. Most likely, important nerves that regulate the stomach’s emptying are cut during the operations. In this procedure:

A surgeon creates a small pouch at the top of the stomach. This pouch becomes the new stomach that is small in volume.
Surgeons then connect the new pouch to the middle part of the small intestine, bypassing the upper part of the small intestine.

After the surgery, the stomach pouch holds a lot less food than a normal-sized stomach. A person will eat less, feel full sooner, and be less hungry. Also, fewer calories and nutrients are absorbed because the small intestine is shorter.
People who get gastric bypass tend to lose more weight, but there can be more problems too.
This procedure not only restricts food intake but also limits the release of hormones in the gut that regulate hunger.

Who is considered good for gastric bypass surgery?

The best candidates for gastric bypass surgery are patients with a high body mass index (BMI) as well as obesity-related health conditions. Such as:

Those with a BMI greater than or equal to 40 kg/m2 or who weighs more than 89 lbs.
Those with a BMI greater than or equal to 35 kg/m2 who have at least two obesity-related conditions. This could include type 2 diabetes, hypertension, or heart disease, among others.
Those who cannot achieve a healthy weight with diet and exercise.

The patients undergoing gastric bypass surgery is a serious commitment to a healthier lifestyle. The patient must:

Greatly change their lifestyle.
Learn to control portion sizes.
Exercise regularly.

What are the long-term issues that occur when having Roux-en-Y gastric bypass surgery?

The long-term issues or complications may include:

Reduction in nutrient absorption following a Roux-en-Y gastric bypass is minimal. The major problem is the iron and vitamin B12 absorption. These need to be supplemented.
Calcium absorption is also reduced and needs supplementation.
Long-term complications of weight-loss surgery include nutritional deficiencies, blockage in the stomach or intestines, leaking or narrowing around the site of the operation, ulcerations at the site of surgery, and depression due to poor quality of life. Because of these and other complications, lifelong medical surveillance is important.

What are the possible benefits after gastric bypass surgery?

The possible benefits may include:

Many people lose half or more of their starting weight especially in the first 2 years after the operation. The average loss is 44 to 66 pounds.
This rapid weight loss quickly translates into improvements in blood sugar, blood pressure, and cholesterol levels in about 9 out of 10 people.
In some, the changes are so great that they can stop taking medicines for diabetes, high blood pressure, or high cholesterol. However, these benefits last only if the weight stays within limits.