Understanding weight loss after bariatric surgery

1. Understanding Weight Loss
After Bariatric Surgery
Statistics, Random Distribution and
Too Little or Too Much of a Good Thing

2. The Goal of Weight Loss
Surgery
Weight Loss

3. The Goal of Weight Loss Surgery:
• Weight Loss, Of Course
But Not Too Much and
Not Too Little

4. Bariatric Weight Loss Surgery
A History of Failure
Jejuno-ileal Bypass
Horizontal Gastroplasty
Vertical Banded Gastroplasty
Lap Band
? Sleeve/RNY/BPD etc.?

5. Judgement of the Success or Failure
Many Factors might be used to judge the success
or failure of Weight Loss Surgery

6. Weight Loss
Because of Convenience and Publications
% Excess Weight Loss (Imperfect)

7. Data Collection
Review of published series
Survey of participating Surgeons
For the purpose of this study
Operation Type, %Excess weight loss
(Mean and Standard Deviation)

8. Explanation: Mean
Mean= Power/Effectiveness of a Group of
results calculated average of the measurements:
a calculated "central" value of a set of numbers.
To calculate: Just add up all the Measurements,
then divide by how many Measurements there are.

9. Explanation: Standard Deviation
Standard deviation is a number used to tell how
measurements for a group are spread out from the
average (mean), or expected value.
A small standard deviation means that most of the
Measurements are very close to the average.
A high standard deviation means that the
Measurements are spread out.

10. “Normal Distribution”
A graphical representation of a normal distribution
is sometimes called a bell curve because of its flared
shape. ...
All normal distributions look like a symmetric, bell-
shaped curve

11. Bell Shaped Curve Normal Distribution
Mean

12. Mean, Normal Distribution, Standard Deviation

14. Survey: Total# MGB/OAGBs you have done?
Number Surgeons: 27
Average: 398
Total: 10,751

15. Survey/Review Percent XsWtLoss
Mean = Power, SD = Accuracy
Mean S.D.
Band 45% + 23%
Sleeve 58% + 24%
RNY 72% + 23%
MGB 78% + 22%
BPD/DS/ 82% + 24%

16. Do You Measure the Entire Bowel Length?

17. What is the MEAN length of the bowel in your experience
Mean 686 cm 22.5 ft
Standard Deviation 138 cm 4.5 ft

18. MEAN Bilio-Pancreatic Limb Length in CM, Centimeters
Min 150.00
Max 253.00
Median 200.00
Mean 195.19

19. DS-XWL-Mean: Mean Excess Weight Loss
Mean XsWL: 84%

20. Survey/Review Percent XsWtLoss
Mean = Power, SD = Accuracy
Mean S.D.
Band 45% + 23%
Sleeve 58% + 24%
RNY 72% + 23%
MGB 78% + 22%
BPD/DS/ 82% + 24%

21. Percent XsWtLoss, SD = Accuracy
All Roughly the same!
Mean S.D.
Band 45% + 23%
Sleeve 58% + 24%
RNY 72% + 23%
MGB 78% + 22%
BPD/DS/ 82% + 24%

22. Percent XsWtLoss, SD = Accuracy
All Roughly the same!
Mean
S.D.
Band 45% +
23%
Sleeve 58% +
24%
RNY 72% +
23%
MGB 78% +
What Does this Mean?
It means all forms of Bariatric
Surgery vary in POWER
(Band<Sleeve<RNY<MGB<BPD-SADI)
But
All are roughly
Equally Inaccurate

23. Calculating Risk of Malnutrition/Excess Weight Loss
1.Power of Bariatric Surgery = Mean Excess Wt Loss
2.S.D. = “Spread” of the Patients Weight Loss
around the mean
3.If we define Malnutrition/eXcess WL (MXWL) =
Loss of 120% of Excess Body Weight (XBW)
4.Then we can calculate risk of Malnutrition/eXcess
WL (MXWL) for each bariatric operation

24. Lap Band: Risk of Malnutrition/Excess Weight Loss
1. LapBand Mean Excess Wt
Loss: = 45% **
2. Standard Deviation (S.D.) =
23%
3. Malnutrition/eXcessWL
(MXWL) = Loss of 120% XBL
4. Band: Risk
Malnutrition/eXcess WL
(MXWL) = 0.06%

25. Sleeve: Risk of Malnutrition/Excess Weight Loss
1. Sleeve Mean Excess Wt Loss:
= 58% **
2. Standard Deviation (S.D.) =
24%
3. Malnutrition/eXcessWL
(MXWL) = Loss of 120% XBL
4. Sleeve: Risk
Malnutrition/eXcess WL
(MXWL) = 0.5%

26. RNY: Risk of Malnutrition/Excess Weight Loss
1. RNY Mean Excess Wt Loss: =
72% **
2. Standard Deviation (S.D.) =
23%
3. Malnutrition/eXcessWL
(MXWL) = Loss of 120% XBL
4. RNY: Risk
Malnutrition/eXcess WL
(MXWL) = 1.8%

27. MGB (2M bypass): Risk of Malnutrition/Excess
Weight Loss
1. MGB (2M bypass) Mean
Excess Wt Loss: = 78% **
2. Standard Deviation (S.D.) =
24%
3. Malnutrition/eXcessWL
(MXWL) = Loss of 120% XBL
4. MGB (2M bypass): Risk
Malnutrition/eXcess WL
(MXWL) = 3.4%

28. BPD/SADI etc: Risk of Malnutrition/Excess Weight
Loss
1. BPD/SADI etc Mean Excess
Wt Loss: = 82% **
2. Standard Deviation (S.D.) =
24%
3. Malnutrition/eXcessWL
(MXWL) = Loss of 120% XBL
4. BPD/SADI etc: Risk
Malnutrition/eXcess WL
(MXWL) = 5.7%

29. Calculating Risk of Malnutrition/Excess Weight Loss
Op Risk XS
Wt Loss
Band
0.06%
Sleeve
0.5%
RNY
1.8%
MGB (2M bypass) 3.4%
Two Important Points to Note:
1. MGB with 2 meter (6 foot
Bypass)
2. BPD/SADI etc
NO More Accurate
than other operations that
DO NOT MEASURE THE
COMMON CHANNEL

30. Calculating Risk of Malnutrition/Excess Weight Loss
1. Since the power (Mean XWL)
varies by procedure and the
s.d. stays roughly the same
(B<S<R<M<Bpd)
2. This means with greater power
(Mean %XWL) the risk of
Malnutrition/Excess Weight Loss
Increases.
(B 0.06<S 0.5<R 1.8<M 3.4<Bpd 5.7)
Two Important Points to Note:
1. MGB with 2 meter (6 foot
Bypass)
2. BPD/SADI etc
NO More Accurate
than other operations that
DO NOT MEASURE THE
COMMON CHANNEL

31. MGB Uniquely Qualified to Allow Patient and
Surgeon to Address Power & Surgery Risk
Modulating Risk of Malnutrition/Excess Weight Loss
Study Demonstrates Power and Risk of
Malnutrition/Excess Weight Loss
MGB Allows patient and surgeon to titrate operative
choices based upon preferences and secondarily to
easily address post op excess weight loss or
malnutrition

32. MGB (1.5 vs 2.0 BP Limb) titrate operative choices
Similar this survey MGB surgeons have reported on rates of Post
Op Malnutrition and excess weight loss requiring reoperation:
Results: Risk of Malnutrition/Excess Weight Loss
MGB BP Limb of 2 meters eXcess WL
requiring revision surgery 1%
MGB BP Limb of 1.5 meters eXcess WL
requiring revision surgery 0.1%

33. MGB: Patient and Surgeon Choice
MGB with BP Limb of 2 meters for Maximal weight
Loss and approximately 1-3% risk of excess weight
loss
Or
MGB with BP Limb of 1.5 meters for Less weight
Loss and approximately 0.1% risk of excess weight
loss

34. The Myth of the Common
Channel

35. Myth of the Common Channel
Measuring the Common Channel will improve the
outcomes (accuracy of weight loss) following
bariatric surgery
1.No supporting evidence
2.This study shows procedures/surgeons using the
common channel DO NOT improve weight loss
accuracy

36. Preliminary Conclusions
1. Bariatric Operation based on published reports and survey data
are more or less powerful
Band < Sleeve < RNY < MGB < = BPD/SADI etc
2. All Bariatric Procedures studied are roughly equally
accurate/inaccurate
3. Measuring the Common Channel as part of bypass operation
does NOT appear to improve or affect Accuracy of Bariatric
Procedures