A new report draws a direct line between alarming obesity rates and sharp increases in knee and hip replacement surgeries.

Experts warn this should be a wake-up call for Canadians concerned about the health of their joints -- and the cost of their health care.

The report, from the Canadian Institute for Health Information, said people who were obese had joint replacement surgery at three times the rate of people with a healthy body weight.

People who were overweight were twice as likely to undergo joint replacement as individuals with a healthy weight.

The report, based on figures from 2003-04, showed that nine of 10 people who had a knee replacement were overweight or obese and seven of 10 people who had a hip replaced were in those weight categories.

It has been known for some time that carrying excess weight puts individuals at risk of developing osteoarthritis, a condition that can lead to the need to replace knee or hip joints. And it has been known that the number of Canadians undergoing these operations has risen sharply in recent years.

In fact, the report notes the total number of these surgeries has doubled over the last eight years. That increased demand has led to long wait times for joint replacement operations.

A report on surgical wait times in Ontario earlier this year said patients waited an average of 33 weeks for knee replacement surgery and 24 weeks for a hip replacement

An orthopedic surgeon whose practice is entirely devoted to joint replacements said the report represents the first time there were numbers to show that people who weigh more are more likely to need joint replacements. And Dr. Olga Huk of Montreal said the correlation is concerning when viewed in the context of the aging baby boomers, many of whom are approaching later life with more than a little excess baggage.

Forty-six per cent of people who had a joint replacement were considered obese, defined as having a body mass index of 30.0 or higher.

About 35 per cent of the joint replacement patients were considered overweight, meaning their body mass index ranged from 25.0 to 29.9.

Only 18 per cent of the joint replacement patients had what was considered an acceptable weight, a body mass index of between 18.5 and 24.9.