Sunday, December 5, 2010

How do you spell "success" after bariatric surgery?

The sweet smell of "success" . . . it's so intangible, so personal, so dependent on the point of view. Here's a sampling of what I have heard from patients:

"I can buy clothes in a regular department store!"
Often after years of buying shapeless clothes in specialty stores, many people - women and men! - enjoy trying on clothes in a department store, feeling stylish and reveling in colors other than black.

"I don't need a seat belt extender on airplanes anymore! And I actually fit into the seat properly."
Many post-bariatric-surgery patients start flying again after many years of staying at home because of shame at the ordeal of negotiating the seat constraints. Attending far-away family events suddenly becomes possible and taking vacations just for the fun of it becomes part of the normal routine.

"I don't have to wear my CPAP mask anymore!"
CPAP stands for Continuous Positive Airway Pressure and the mask is attached to a machine that pumps air into and out of the nose throughout the night. It is the work-around of choice for a condition known as sleep apnea. Wearing a CPAP mask is nobody's idea of a good time, but waking up refreshed and having energy throughout the day makes the ordeal worthwhile for many people. Obesity is a significant risk factor for sleep apnea, and it often clears up after weight loss. Sleeping without the mask and the machine represents a dramatic improvement in quality of life for many people.

"I'm off all my medications!"
Other conditions that often clear up after weight loss or simply after gastric bypass (see previous posts) include Type 2 diabetes, hypertension, high cholesterol, and psoriasis. Fewer medications means saving money, time and trouble. And individuals may feel a sense of greater autonomy over their own health.

Which brings us to the question of point of view . . . how do researchers define success after bariatric surgery? After all, the outcomes measured for a research study must be quantifiable. And, while there are questionnaires that assess a person's quality of life, today we are going to examine a study that looks at weight loss only.

Specifically, a way of measuring weight loss not in pounds, but expressed as a percentage of the weight an individual needs to lose. For example, if an individual weighs 300 pounds, and the ideal weight is 200 pounds, then 100 pounds is the excess body weight (EBW). If the person has now lost 40 pounds, then the percentage of excess weight that has been lost is 40%.

ResearchBlogging.orgSnyder, B., Nguyen, A., Scarbourough, T., Yu, S., & Wilson, E. (2009). Comparison of those who succeed in losing significant excessive weight after bariatric surgery and those who fail. Surgical Endoscopy, 23 (10), 2302-2306. DOI: 10.1007/s00464-008-0322-1

In this study, "good weight loss" was defined as >= 50% EBW, and "poor weight loss" as <= 30% EBW within the first year after surgery. They included patients who had had gastric bypass and gastric banding procedures.

There are problems right off the bat. First, these are not generally accepted definitions, and the authors provided no justification for their choices. And, in general, I am always wary of analyses that throw out data. Why not include all the data in a linear analysis rather than creating 2 extreme groups? This question was not addressed.

Second, weight loss in and of itself is not necessarily the best definition of success. Ultimately, it is lifestyle change that allows patients to maintain weight loss.

Third, the most obese patients likely did not have enough time to lose 50% EBW. In other words, we might predict that the "good weight loss" group is going to be disproportionately made up of people who started out with a lower BMI. And this is exactly what was reported in the study for both gastric bypass and banding groups.

And fourth, the timelines for weight loss differ based on the procedure performed, that is, gastric bypass patients generally experience a drastic weight loss in year 1, tapering off to their maximum at the end of 3 years, and gastric banding patients see a more steady curve over those first 3 years. Often the results at the end of 3 years are similar, but that first year looks very different based on the procedure.

Again, this is exactly what was reported. Among bypass patients, 75% achieved "good weight loss" and only 5% had "poor weight loss." Fine, but this represents the period of most dramatic weight loss for this group. Among banding patients, only 27% achieved "good weight loss" and 34% had "poor weight loss." But when the banding patients have time to reach their potential, who knows how this comparison would turn out?

I was hoping to learn some useful distinctions about success and failure from this study, but, alas, that was not to be. Here's what I'll be looking for in the future:

First, a more robust definition of success after bariatric surgery, including %EBW lost, objective improvements in pre-existing medical conditions, and subjective improvements in quality of life.

Second, the inclusion of life style changes in the prediction of success. For example, how do exercise, dietary choices, and adherence to nutrition supplements contribute to long-term weight loss?

Third, the selection of a dataset that allows for meaningful comparisons. For example, the validity of a study comparing bypass and banding patients would be strengthened by using a follow-up period of 3 years.

1 comment:

  1. Wow, this is pretty interesting. Inspiring, as well. Thanks for sharing such inspiring experience with us. Great blog, congrats.!