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Gastric Bypass & Bone Fracture

July 2009

Newsletter from Dr David Ashton

Medical Director, Healthier Weight

 

Hello! 

Here at Healthier Weight we take the aftercare of obesity surgery patients extremely seriously. 

Following a recent, well publicised study, I am keen to look at the impact gastric bypass surgery has on patients' bones. In my newsletter for this month I have written a brief overview of the study and comment on its findings:

A study presented at the 91st Annual Meeting of the Endocrine Society in Washington DC in June 2009, suggests that patients undergoing weight loss surgery may be at an increased risk of bone fracture. 

Researchers from the prestigious Mayo Clinic reviewed the medical records of patients who had weight loss surgery between 1985 and 2004.  They were especially interested in records pertaining to bone fracture during this period. Thus far the authors analyzed data for 97 of the 292 patients whose records are available. 

Of the 97 patients, 86 were women, and their average age was 44 years. Ninety percent of the patients had the most common type of weight loss surgery—gastric bypass— whilst the remainder had gastric banding or biliopancreatic diversion. The average length of follow-up was 7 years.  

Of the 97 patients, 21 suffered one or more fractures, for a total of 31 fractures.  Compared with the fracture rate expected in an age- and sex-matched population, the patients who underwent obesity surgery were almost twice as likely to have a first fracture at any site of the body.  Fractures were especially common in the hand and foot, with the risk of hand fracture being more than three times greater than average, and foot fracture risk nearly four times greater.
 

Healthier Weight Comments

There is a certain irony in these findings in that being overweight is usually protective against osteoporosis, because weight-bearing strengthens the bones (possibly the only positive thing you'll ever hear a doctor say about being overweight!)   So, at least in terms of bone health, the overweight and obese start off better than normal weight patients. The question is whether they end up with worse bones and, if so, why? 

One obvious possibility is that most of the patients in the study had a gastric bypass, which is known to reduce the absorption of calcium through the bowel.  Lack of calcium could produce thinning of bone and an increased risk of fractures.  However, it is notable that in this study the site of the fractures – hands and feet – is not typical of osteoporotic fractures which usually occur in the hip or spine.  Another possibility is that as body weight falls, post-surgery patients go through a transition period during which their bones adjust to a new body weight. 

But could it be simply that as they lose weight, post-surgery patients begin to enjoy a much more active lifestyle – cycling, swimming, running etc- which would increase the risk of fracture even in those with normal bones?  This would explain why, in this study, most of the fractures occurred in the feet and hands.  I remember a gastric bypass patient of mine who lost 120lbs and took up skiing; when he attended the clinic for a 2-year follow-up he had one of his legs in a cast having fractured his ankle during an alpine skiing holiday. 

Clearly more research is needed to clarify the mechanisms involved.  We also need to know whether similar findings would apply to gastric banding which has much less in the way of calcium malabsorption compared with gastric bypass.  We also need to know whether the bones of teenagers react in a similar way, given the increasing numbers of adolescents likely to undergo weight loss surgery in the coming years.  Whatever the mechanisms involved, this study emphasizes the point that careful monitoring and lifelong follow-up are essential to long-term wellbeing following obesity surgery. 

See our Gastric Bypass Extended Aftercare section

 

Dr David Ashton MD PhD, Medical Director, Healthier Weight Centres 

Haglind E.  Bone fractures following bariatric surgery.  Paper presented at the 91st Annual Meeting of the Endocrine Society, Washington DC, June 2009

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