Carrying extra weight may damage your spine

By Anna Sayburn

BMJ Group News

What do we know already?

Damage to the discs that cushion the spine can cause back pain, if the discs squeeze the nerves that run to and from the spinal cord. Studies have shown that disc damage can be caused in many ways, including age-related wear and tear, putting strain on the back through heavy lifting or physical work, and even through the genes you inherit from your parents.

It seems logical that carrying a lot of body weight might also put more strain on the spine. But there has been no clear research linking body weight with disc damage, until now.

In this big study, 2,600 volunteers aged 21 to 63 were recruited, had their weight and height measured to calculate their body mass index (BMI), and underwent MRI scans of their spine. Experts checked the MRI scans for signs of disc damage and the extent of the damage. Researchers then compared the results to see if BMI was linked to disc damage.

What does the new study say?

People who had at least some disc damage had an average BMI higher than people without disc damage. The average BMI for people without disc damage was in the normal range, and the average BMI of people with disc damage was in the overweight range. However, most people in the study (73 in 100) had some form of disc damage, so this doesn’t tell us very much.

More interestingly, when researchers looked at the extent of damage to discs, they found that damage tended to increase in line with people’s BMI, so that higher BMI tended to go hand in hand with worse damage. This is important, because small amounts of disc damage may not cause any problems. But we know from other studies that more severe damage is more likely to cause back pain.

People who were classed as obese had about a 70 percent increase in their chances of having severe disc damage, compared with people with a normal BMI.

How reliable is the research?

The study was done using a good design, and the researchers adjusted their results to take account of things such as physical workload, exercise activity, and any previous back injury. This makes the results more reliable.

However, the study was carried out in China. The BMI measurements for the ranges ‘normal’, ‘overweight’, and ‘obese’ are slightly different for Asian countries, to take account of physical differences. We can’t be completely sure that the results will apply in the same way to people in the UK.

What does this mean for me?

If you want to protect your spine from damage, this research suggests it’s a good idea to keep your weight in a healthy range. However, it still doesn’t prove that excess weight causes back pain, and there may be other issues that have not been taken into account.

We don’t know from this research whether losing weight can help if you are overweight and already have back pain. However, there are lots of good reasons to aim for a healthy weight, including a reduced chance of heart disease and some cancers.