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Obesity and skeletal health

Studies show link between obesity and skeletal health

Credit: staff "Blausen - "Blausen gallery 2014". Wikiversity Journal of Medicine
Obesity has a higher risk for surgery in orthopaedic trauma patients and patients with obesity had longer hospital stays and greater treatment costs
They found obesity and Type 2 diabetes negatively affected bone, but exercise prevented weight gain and diabetes and increased bone strength

Two published studies have demonstrated the negative impact obesity and metabolic disease can have on skeletal health. The first study published in the Journal of Bone & Joint Surgery (JBJS) has found a link between obesity and a higher risk for surgery in orthopaedic trauma patients. In addition, researchers found that patients with obesity had longer hospital stays and greater treatment costs. They were also more likely to be discharged to a care facility, rather than to home.

In the study, researchers used computer tomography (CT) scans to measure truncal BMI - body fat volume in a patient's midsection. They sought to determine whether a possible relationship existed between obesity and an increasing health care burden in patients with multiple orthopaedic traumas.

Researchers identified 301 patients with multiple orthopaedic injuries at a Level I trauma centre from 2006 to 2011. Patients with a truncal BMI<30 were categorized as non-obese, and those who measured >30 were considered obese. The patients with obesity were further divided into two classes. Class I included patients with a truncal BMI 30-35; those with a truncal BMI >35 were in Class II.

Their analysis showed that:

  • Obesity increased the risk of surgery: 72 percent of the obese patients required surgical treatment, compared to nearly 55 percent of non-obese patients. The degree of obesity also had an impact on a patients risk for surgery. Although 67 percent of Class I patients had surgery, 93.3 percent of the Class II patients required surgery.
  • Patients with a normal truncal BMI had shorter hospital stays. Their mean intensive care unit stay was 7.2 days and the mean total hospital stay was 12.4 days, compared to 9.7 days and 16.4 days for patients diagnosed as obese.
  • Mean hospital costs were US$160,606.02 for non-obese patients and US$234,863.58 for obese patients.
  • A greater proportion of Class II patients required discharge to a continuing care facility.

"Overall this study found an association between obesity and increased rates of lower-extremity injuries and orthopaedic surgery," said study lead author and orthopaedic surgeon, Dr Heather Licht. "Obese patients had higher total hospital charges, longer intensive care unit and total hospital stays, and decreased rate of discharge. Even when patients have the same severity of injuries, resource utilization is higher among patients with obesity, compared to non-obese patients.”

Metabolic disease and bone health

In a separate animal study, University of Missouri researchers examined how the development of obesity and insulin resistance contribute to bone-fracture risk and whether exercise prevents weight gain and diabetes and protects bone health. They found obesity and Type 2 diabetes negatively affected bone, but exercise prevented weight gain and diabetes and increased bone strength. These findings could inform interventions to improve bone health among individuals with obesity and Type 2 diabetes. The findings, ‘Obesity-related changes in bone structural and material properties in hyperphagic OLETF rats and protection by voluntary wheel running,’ were published in the journal Metabolism.

"Researchers once thought obesity was protective of bone because with more body mass, individuals have more bone mass; more bone mass typically decreases risk of osteoporosis and associated fractures," said Pam Hinton, an associate professor in the MU Department of Nutrition and Exercise Physiology. "What we've come to realise is that the bone of people with obesity and Type 2 diabetes isn't good, quality bone. These individuals have an increased risk of fractures, so that extra body weight isn't protective."

Hinton and her colleagues examined how the development of obesity and Type 2 diabetes affect bone structure, formation and strength over time. Specifically, the researchers studied the bones of rats that had a predisposition to overeat, which caused the rats to gain weight and become insulin resistant. This pattern of weight gain and insulin resistance parallels the development of obesity and Type 2 diabetes in humans, Hinton said.

The researchers allowed half of the rats to overeat and voluntarily exercise on running wheels; the other rats programmed to overeat remained sedentary. The researchers also had a control group of non-overeating rats that remained sedentary. The researchers studied bones from rats in the three groups at different ages to determine how early in the development of obesity and diabetes the bone was affected negatively.

"As the rats continued to grow, all groups increased their bone mass, but the rats that were obese and sedentary didn't accumulate as much bone mass relative to their body weight," said Hinton. "So, decreased bone formation, loss of bone mass and decreased bone strength all were present in the obese, diabetic, sedentary rats. However, the rats that exercised did not lose bone strength. In fact, the rats that ran on the wheels had stronger bones than the normal-weight controls."

This study doesn't explain how exercise increased bone quality, Hinton said. The animals in the exercise group were healthier; they didn't develop the same insulin resistance and diabetes, which might explain why the bones of the exercising rats were healthier, she added.

"Once we can identify why bones in individuals with obesity and Type 2 diabetes are weaker and how they become weaker, we can start developing more treatments through lifestyle and behavioural changes.”

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