Expected Weight Loss after Bariatric Surgery


How much weight should I be losing?
Am I losing weight fast enough?
Questions similar to these are asked everyday in my office.
Let’s dive into some research for realistic expectations and mathematics to answer this question for each of you.

So here’s the research:
RNYGB patients are predicted to lose 70-80% of their excess weight by 18 months post-op.  By 15 years post-op, maintaining the loss of 60-65% of excess weight is considered successful.  Most people do not maintain the lowest weight they achieve; it’s normal to gain a small amount of weight typically between 3-5 yrs post-op.

SG patients are predicted to lose 55-60% of their excess weight by 5 years post-op.

Another marker of success is to stabilize in an overweight BMI category.  Most of you want to get to your dream weight and be in a normal BMI category but WLS does not get rid of 100% of your excess weight.  Unrealistic expectations can lead to feeling like a failure or sabotaging your success.  Remember to also measure your success by how much better you feel physically and how you’re able to move more comfortably in your body.

You’ll need a few numbers to answer “how much weight will I lose after bariatric surgery” including your pre-op weight, ideal weight and excess weight.

Pre-Op Weight – Ideal Weight = Excess Weight
Excess Weight x 65% = Expected Weight Loss
Pre-Op Weight – Expected Wt Loss = Expected Goal Weight

Patient is 5’8″ with pre-op wt of  375 lbs.
On a BMI chart, his ideal wt at a 24 would be 158 lbs.  Subtracting 158 lbs from 375 lbs determines he’s carrying 220 lbs of excess weight.
Multiple 220 by 65% and this patient can expect to loose a total of 143 lbs.
Subtract 143 lbs from starting weight of 375 lbs gives patient a goal weight of 232 lbs.

Check out this resource via Obesity Help; it calculates expected weight loss for you: http://www.obesityhelp.com/morbidobesity/information/planner+results.php

Keep in mind, these calculations are averages, not guarantees.  Lifestyle habits such as meal planning, reading labels, food tracking, staying hydrated, vitamin compliance and moving your body are all significant factors in improving your health and maximizing your weight loss.  Use your bariatric dietitian for education, support and accountability!



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