Bariatric surgery, which significantly curtails the amount of food a person can eat, is the most effective treatment against obesity and is being recognized as a potentially valuable tool in the fight against diabetes related to obesity. It is being performed on increasing numbers of people worldwide, including teenagers.
Unfortunately, some types of bariatric surgery may also cause bone loss, a cause for concern, particularly when carried out on young people who have not yet reached their peak bone mass, say endocrinologists from Sydney's Garvan Institute of Medical Research, who have just published a review of current literature in the journal Obesity Reviews, now online.
Authors, Dr Malgorzata Brzozowska and Associate Professor Jackie Center, say that skeletal examination and treatment should be considered part of patient care, before and after procedures.
In the United States, 'Roux-en-Y' gastric bypass surgery, one of the most invasive of the procedures, is the most common. Much of the stomach is removed and part of the small bowel bypassed. Less radical is the 'gastric sleeve', which involves removing a large part of the stomach leaving a narrowed smaller stomach, restricting food intake and at the same time speeding the passage of food to the gut. The least invasive, and only reversible measure, is the 'gastric band', which is an inflatable ring placed between the oesophagus and stomach, making it possible to eat only small amounts of food slowly.
"Even though we don't yet understand all the mechanisms, we can see that the more radical the procedure, the greater the bone loss long-term," said Dr Brzozowska, who undertook the review as part of her PhD.
Dr Brzozowska is the first person to do a widespread analysis of current research into the complex interrelationships between fat, bone and nutritional restriction.
"In many situations significant weight loss is associated with bone loss, with or without surgery. The more invasive types of surgery appear to heighten bone turnover and the associated bone loss. This is thought to be caused not only by rapid weight loss and absorption of fewer vital nutrients like vitamin D and calcium, but possibly also by changes in hormones released by fat and the gut, and their impact on the central nervous system," she said.
In particular, the review points out, we should be aware of surgery-induced changes in hormones that can affect the central regulation of appetite and bone strength. These include the fat-derived hormones leptin and adiponectin; gut-derived hormones such as peptide YY (PYY), glucagon-like peptide 1 (GLP-1) and ghrelin; and the hypothalamic regulator of energy balance, neuropeptide Y (NPY). However, although there is quite a lot of animal data concerning these hormones and their effects, human data are scanty.
Associate Professor Jackie Center believes that the findings are very important despite the widely held assumption that obese people are protected against bone fragility and fracture.
"It has always been assumed that the heavier someone is, the denser their bones will be, because bones become strong when they carry a load. While that is true up to a certain point, the bones may not continue to become stronger in the very obese, who can also have low bone density and fracture.
"Increasing evidence suggests that in very obese people, the relationship between bone density and weight fails and that the excess fat is detrimental to bone.
"While there are many studies looking at weight loss and improvement in insulin sensitivity after bariatric surgery, very few look at what happens in bone.
"We are certainly not arguing against bariatric surgery. There is no doubt that it is an effective weapon against obesity and obesity-related diabetes. We just ask that doctors and patients take bone health into account.
"Bone mineral densitometry scans can be done and adequate calcium and vitamin D intake advised. For those patients at particular risk, additional monitoring may be advised and protective drugs considered."
Research Australia: http://www.researchaustralia.com.au
This press release was posted to serve as a topic for discussion. Please comment below. We try our best to only post press releases that are associated with peer reviewed scientific literature. Critical discussions of the research are appreciated. If you need help finding a link to the original article, please contact us on twitter or via e-mail.
A second child seems to have been cleared of the AIDS virus, thanks to heavy-duty drugs started just hours after birth. This spring researchers plan to test that approach in 60 more newborns.
A report finds that azodicarbonamide wasn't just in Subway's bread: It's in hundreds of foods. While it has been linked to asthma in factory workers, the additive poses no known risk to consumers.
Army initiative to research suicides in the US military released its first three studiesAmanda Holpuch
The luxury fibre can be fashioned into screws and plates that could hold broken bones together while they heal, before biodegrading when no longer needed
Middle-aged people on a high-protein diet are at greater risk of dying from cancer, claims a study, but critics say firm evidence is lacking
In an exclusive interview with National Geographic, Nora Volkow, director of the National Institute on Drug Abuse, shares her concerns about the consequences of legalizing the drug.
Tailor-made medical devices could give a more detailed picture of cardiac health and may be better at predicting and preventing problems.
People around the world are eating a wider range of foods. But as a whole, we are increasingly reliant on a few crops. Researchers say that increases the risk of agricultural disaster.
Mushrooms are being hailed as a miracle cure for cancer. But can a shiitake stir-fry really work wonders?
Elder care is a booming business, but someone has to pay. Seniors and their children shouldn't have to go bankrupt for care