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Gastric Bypass Expected Weight Loss

Gastric Bypass Expected Weight Loss

You will lose a significant amount of weight after your gastric bypass surgery.  The average amount of excess weight lost is 70%.  Most patients lose between 60% and 80%.  This weight loss surgery treats severe obesity, but it is not a magic cure. It is a daily reminder of the permanent decision you made to improve your health.

Weight loss surgery requires you to make significant changes to your lifestyle.  To maintain your weight loss, you must make positive changes to your life for permanent results.  These changes include a healthy diet and a regular exercise routine.  Bariatric surgery is only a tool, but the work you put into your life after surgery is the most important.  You will lose weight quickly within your first year after surgery, but your weight will eventually slow down.

Your weight loss surgery does not replace or fix bad lifestyle habits.  Many patients find it helpful to discover and understand their relationship to food before surgery to help better prepare them for their life afterward.  A negative relationship with food includes eating when you are bored, lonely, tired, angry, or sad.  Trying to escape these emotions by overeating after surgery is a bad idea.  It can lead to unnecessary weight, regain and halt your progress. Allowing yourself time and patience to understand your emotional triggers with food is helpful.  You will need time to train your mind not to want as much food.

Prepare yourself with time to research and evaluate your surgery options.

Gastric Bypass Facts

The gastric bypass surgery includes attaching a small pouch to your intestine to bypass your stomach.  Gastric bypass is generally recommended to obese patients with a body mass index of over 40—the recovery time averages between two to four weeks.

A side effect that can occur after the surgery is dumping syndrome.  This happens when you eat too quickly, and the foods usually are too sugary and fatty for your digestive system to process.  Other possible complications are infections, intestinal complications, and blood clots.

Gastric Bypass Weight Calculator

Your weight loss after your gastric bypass surgery depends on many factors.  These factors include your age, exercise, lifestyle, and commitment to changing old habits.  Also, the size of your new stomach can make a small difference in your weight loss.

Your gastric bypass surgery creates many permanent dietary changes.  This is why you can lose more weight than other procedures.  On average, the gastric bypass patient loses 70% of their excess weight.

Your Expected Weight Loss

To calculate this --

What is your ideal weight?

How much excess weight do you have to lose?

  • Current Weight - Ideal Weight = Excess Weight

How to calculate your expected weight loss:

  • Excess Weight x .70 = Expected Weight Loss

How to calculate your new weight:

  • Current Weight – Expected Weight Loss = New Weight After
Your weight loss depended on many factors; take it one day at a time.

To lose the average amount of weight, follow the strict guidelines your bariatric health care team has for you pre and post-operation.

Be mindful that losing 70% of your excess weight is an average amount.  Some people lose less, and some lose more.

The hardest part is losing the first fifty pounds of weight.  This is during your all liquid phase and can be extremely painful and challenging to do. This is right after surgery, and you may be in pain, making your drinking habits hard to digest.

After you lose your first fifty pounds, you will start to notice a visible difference in your appearance.  You will begin losing pounds and inches off of your body.  This will make all of your pain feel worth it because you will begin to start and feel better.

Short Term Weight Loss

Gastric Bypass patients can lose, on average, 10 to 20 pounds for the first month after surgery.  These results vary depending on your age, health, and starting weight.  Rapid weight loss also puts into remission your high blood pressure, high cholesterol, heart disease, and Type II diabetes.

A healthy diet is critical for long term success in your bariatric journey.

Long Term Weight Loss

The U.S. National Library for Medicine National Institutes of Health did a 15-year study on gastric bypass patients.  This study examined patients with a BMI of over 43 and their ability to maintain their weight loss.  On average, these patients were able to keep off 46% of their excess weight.

This study shows that gastric bypass is a successful surgery in treating severe obesity effectively.  To determine a surgery’s success, you need to not just look at the short term weight loss, but also the long term weight loss.

Weight Regain

Weight regain is a regular aspect of gastric bypass surgery.  It is common for some patients to regain a small portion of their weight before their weight stabilizes at their goal weight.  This amount of weight ranges from 10 to 20 pounds.  You may also gain more weight after surgery is you are unwilling to change your lifestyle and eat a healthy diet.

Regular exercise helps tackle daily stress and maintain your goals.

My Weight Loss Experience

At the beginning of my bariatric journey, I was not given a specific amount of weight I would lose.  My health care team stated that due to many factors predicting my weight loss would not be possible. Every person reacts differently to bariatric surgery.  Knowing this before I had gastric sleeve surgery made me curious about how my body would respond.

Now 20 months post-op, I have my answer.

My weight loss experience is comparable to a gastric bypass patient’s experience.  I had the gastric sleeve surgery over 20 months ago and was able to lose over 67% of my excess weight.  I have kept this weight loss off for over seven months.  My ability to maintain the weight loss is due to a healthy diet of focusing on protein and daily exercise. My daily exercise includes cardio, weight training, and yoga. Along with my daily habits for my body, maintaining strong mental health allows me to maintain my determination and willingness to stick to my health plan.

Always be gentle with yourself; it is okay not to be perfect while on this journey.


Many bariatric patients lose their drive and willingness to put in daily effort due to their significant weight loss.  When you lose your concentration, it is easy for harmful and self-destructive habits to creep into your life.

Having a healthy, supportive community to keep you on track with your weight loss goals and efforts is essential in maintaining your long-term weight loss.  Your surgery was not a magic cure for your obesity.  Your weight loss journey relies on your choices and your choices alone.

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Kelsey Renae Schulze

Author

Kelsey is a post-op bariatric patient who had sleeve surgery in 2018. She is a writer, focusing on a variety of topics given her background in legal studies and criminal justice.