Doctor Measuring Obese Man's Waist

If obesity is such a risk factor for your knee operation, why does more and more research suggest it isn’t? Jim Newman looks at the politics behind the story.

Every month you’ll come across a new piece of knee replacement research that suggests obesity isn’t quite the risk factor we once thought it was. This is rather strange because lots more research continues to support the case that obesity increases the risk of complications short and long term.

That increased weight is related to increased risk has been the direction of travel of research findings for years. And actually, even without the data, we surely all intuitively know that undergoing any operation when your body mass index (BMI) is above 35 is bound to be a riskier undertaking than when it’s below 25.

So why the change? And why now?

It’s interesting to see that the research suggesting obesity is less of a risk factor comes primarily from the US and the Middle East, parts of the world which have two things in common: high levels of morbid obesity and an insurance driven private healthcare system.

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The weight of the world

Contrary to conventional wisdom, the US isn’t the most obese nation on earth (that’s Nauru) but it does ride high in the league tables. According to World Population Review, the US is 16th, with an average BMI of 28.8. Bahrain, Jordan, UAE, Saudi Arabia and Qatar are all in the top 22. The UK, in case you were wondering, is a relatively svelte 36th.

Overweight Treatment Diagram

Losing weight, losing patients

Let’s take the US as an example. If you are morbidly obese (that is, you have a BMI of 35+) and need a knee replacement, your health insurer is unlikely to agree to the treatment.

Insurers know what everyone else knows: obesity and operations are not good bedfellows. So they instead encourage weight loss, which reduces risk and therefore reduces costs. That makes sense for hospitals too, because hospitals in the US are now responsible for covering the costs of readmission if there’s a problem, and problems are more likely in obese patients.

But as obesity grows and the number of refused knee operations increases, all of a sudden there are a lot of knee surgeons who don’t have patients to treat because they’re all on weight loss programmes and the funding isn’t available to cover their operations.

Changing the narrative

How do you resolve such an issue? Well one way could be to find new evidence that weight is not the risk we once thought it was. Remove weight as a factor by producing evidence that it does not harm outcomes and the chances of more insurers and hospitals approving such procedures increases.

But to date, that evidence – rather unsurprisingly – is unconvincing.

Doctor Talking to Overweight Patient

NHS honesty

That’s one of the absolute benefits of the NHS. We can be honest with patients, and the honest facts are that obese patients reduce the risks associated with their operation and recovery when they lose weight. Such discussions are not easy to have – and we’re not blind to the fact that such things are difficult to hear. But it is the right, fair and honest approach. It’s the safer approach too.

If you’d like to explore options for your knee replacement, please get in touch.

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James Newman

James Newman

Consultant Knee Surgeon at the Yorkshire Knee Clinic

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