New research finds that carrying far too much weight when diagnosed with multiple sclerosis is linked to higher current and subsequent levels of disability within a relatively short period of time. Reverting to a healthy weight may improve clinical outcomes for obese patients with MS, researchers suggest.

Obesity during childhood and adolescence is linked to a heightened risk of developing MS, irrespective of other potential environmental triggers. But it’s not clear if it might also be linked to faster disability progression after diagnosis. 

To find out, researchers drew on 1066 participants with relapsing-remitting MS from across Germany who were taking part in the German National MS study. More than a quarter of them were men with an average age of 33. When MS was diagnosed, 159 patients were obese with a BMI of at least 30. Co-existing conditions associated with obesity (type 2 diabetes, high blood pressure) were reported in 68 patients. Their levels of disability were monitored every two years for a total of six years, using the Expanded Disability Status Scale.

Obesity at diagnosis wasn’t associated with a higher annual relapse rate, or greater build-up of nerve damage, as seen on MRI brain scans, during the six-year monitoring period.

But levels of disability were higher at the time of diagnosis and at each of the subsequent three time points, after factoring in age, sex, and smoking. And the average time it took obese patients to accumulate greater levels of disability was shorter. They reached EDSS 3 at just under 12 months, on average, compared with nearly 18 months for those who weren’t obese. Obese patients were also more than twice as likely to reach EDSS 3 within six years, irrespective of what type of drug treatment they were getting.

The risk of reaching EDSS 3 within six years in this group was again more than twice as high in obese (BMI 30 or higher) patients as it was in those who weren’t, falling to an 84 percent heightened risk after factoring in sex, age, and smoking. Importantly, overweight (BMI 25–29.9) at diagnosis wasn’t significantly linked to higher disability then or subsequently, or with a heightened risk of reaching an EDSS of 3 after six years. 

The researchers acknowledge that BMI was assessed only once at the start of the study while co-existing conditions were limited to type 2 diabetes and high blood pressure, with the number of those affected, small. But previous research has linked a reduction in brain grey matter with obesity.

The study’s authors note that the finding that obesity, but not overweight in MS patients, is linked to a poorer outcome suggests a threshold effect of body mass on disability accumulation in MS, adding that obesity is a modifiable risk factor. The data suggest that dedicated management of obesity should be explored for its potential merit in improving long-term clinical outcomes of patients diagnosed with MS.

The research was published in the Journal of Neurology, Neurosurgery & Psychiatry.