The effect of a gastric bypass operation on family members

Bariatric surgery is the most reliable and effective treatment for the morbidly
obese population. The benefits of a gastric bypass operation include weight
loss, resolution of comorbidities, and improvements in overall mortality and
specifically mortality related to diabetes, heart disease and cancer.
Since the biggest risk factor for becoming an obese child is having an obese
parent and a persons risk of becoming obese is influenced by associating with
obese individuals, it would be interesting to investigate in which way gastric
bypass surgery affects family members. If one member of the family makes
necessary drastic lifestyle changes following surgery, it is possible that
other family members will adopt similar healthy habits.
There are multiple possible effects that the gastric bypass may have on family
members of the patient. These effects may be divided in two broad categories:
1) the so-called *garbage can* effect, the family member of the patient may
actually have an increase in dietary intake and 2) the *mimicking* effect,
which could actually cause a decrease in the non-operated family member*s
weight. It is unknown which of these two effects, if any, will prevail in
patients* family. To our knowledge, only two studies have examined the effects
of bariatric surgery on family members of patients who underwent a gastric
bypass surgery. These studies are however limited as they have a small sample
size.

Primary objective:
To observe the effect of gastric bypass surgery on household members and
partners who live together with the patient on body mass index (measured as
weight/height²) in the first year following bariatric surgery compared to
family members of obese patients visiting the obesity outpatient clinic.


Secondary objective:
To observe the effect of gastric bypass on household members and partners who
live together with the patient in the first year following bariatric surgery
compared to family members of morbidly obese patients visiting the obesity
outpatient clinic on:
- Changes in eating behavior
- Prevalence of obesity in the family
- Change in BMI of the gastric bypass patient with the BMI of the family
members one year after surgery and change in BMI of the obese patient from the
obesity clinic with the BMI of the family members one year after baseline
measurements
- Correlation of family size with change in BMI

In this one year prospective longitudinal control study we will include 100
families of patients receiving a gastric bypass operation in Slotervaart
Hospital and 50 families of obese patients visiting the obesity outpatient
clinic. The duration of the study will be approximately one year or until a
sufficient amount of participants has been reached. To be able to investigate
if gastric bypass surgery has any influence on family members body mass index
and eating behaviour, we also include a control group, 50 families of obese
patients visiting the obesity outpatient clinic. Furthermore, family members of
patients receiving a gastric bypass operation will be requested to complete
eating behavior questionnaires pre-operative at 3 months, 6 months and 12
months after the operation. Family members of patients visiting the obesity
outpatient clinic will be requested to complete the questionnaires at baseline,
6 months and 12 months after operation.
For the proposed study family members of patients receiving a gastric bypass
operation will be asked to fulfill questionnaires assessing sociodemographic
characteristics (including family size), length and weight and eating behavior
preoperatively. Postoperatively, weight and height will be measured in the
patient and the family members 3 times in a one year period. The
postoperatively assessments will be executed at home, where a digital
questionnaire will be filled out and weight and height will be measured, with
telephonic assistance of the researcher (see appendix 1a).
Family members of patients visiting the obesity outpatient clinic will be asked
to fulfill questionnaires assessing sociodemographic characteristics (including
family size), length and weight and eating behavior after patient and family
members signed for informed consent. The patient and the family members will be
asked to measure their weight and height two times in a one year period. The
assessments will be executed at home, where a digital questionnaire will be
filled out, with telephonic assistance of the researcher (see appendix 1b).
This data collection schedule will be long and intensive enough to detect and
explain the influence of gastric bypass on family members. Weight reduction
will be measured trough body mass index (measured as weight/height²) for adults
and with the standardized Z-BMI score for children.

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