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Although the reasons why a higher BMI might lead to increased MS risk are not fully understood, most scientists think that being obese increases overall inflammation in the body. Ildar Abulkhanov/Getty Images
  • According to a new study, people who are overweight with a body mass index (BMI) of 30 or more when diagnosed with multiple sclerosis (MS) have an increased risk of disability.
  • The onset of disability was also accelerated for people with a BMI of 30 or more.
  • Experts note that many treatments associated with MS, as well as decreased mobility, can impact a person’s eating habits and weight.

A recent study published online in the Journal of Neurology, Neurosurgery & Psychiatry found that people with a body mass index (BMI) of 30 or more at the time of a diagnosis of multiple sclerosis (MS) were twice as likely to reach disability within six years, no matter what treatment they received.

Researchers followed 1,066 participants with relapsing/remitting MS in Germany who participated in The German National MS Study. Of the participants, 159 were obese with a BMI of 30 or over at the time of diagnosis, and 68 people had medical conditions associated with obesity, for example, diabetes and high blood pressure. The average age of participants was 33, and about 30 percent were male.

The scientists monitored the participants’ level of disability every two years using the Expanded Disability Status Scale. The scientists found that the levels of disability for people with a BMI of at least 30 were higher. The average time to reach disability was shorter — 12 months compared to 18 months for those who were not obese. This was true even after the researchers factored in age, sex, and smoking status.

“Multiple studies examining childhood and adolescent obesity have found an association between increased BMI and higher risk of developing multiple sclerosis,” says Michael Sy, MD, Ph.D., a neurologist with UCI Health in Irvine, CA. “Simply being overweight carries significant risk, and being obese carries additional risk. Although the reasons why a higher BMI might lead to increased MS risk are not fully understood, most scientists think that being obese increases overall inflammation in the body.”

Being overweight with a BMI of 25-29.9 was not significantly associated with an increased risk of disability within the study follow-up period of six years.

“BMI is not always the best indicator,” says Rachel MacPherson, CPT, Certified Nutrition Coach. “For example, someone with a larger amount of muscle could have a high BMI that is not due to fatty tissue. BMI is also not as accurate for some people, such as people of color. This is also a small study and could provide better information if repeated with more participants.”

The scientists also noted that obesity during childhood and adolescence was associated with a higher risk of developing MS. Still, they did not determine if this was linked to faster disability after diagnosis.

Because this was an observational study, the researchers could not establish a cause-and-effect relationship between obesity and disability in patients with MS.

Obesity, the researchers indicated, is a modifiable risk factor. Losing weight and reaching a healthy weight can improve clinical outcomes.

Some people lose weight after an MS diagnosis, according to the MS Society. This could occur because:

If you do lose weight, you might be at risk of developing nutritional deficiencies. Suppose you find it difficult or you are unmotivated to eat. In that case, your doctor might suggest you see a dietician to help you work on the best foods to eat or whether you could benefit from supplementing your food with nutrients, such as protein.

“A healthy diet has benefits beyond MS, improving general heart and brain health,” Sy told Healthline. “I would recommend talking to both your primary care physician and neurologist about your diet, and if appropriate, they may refer you to a dietician or nutritionist.”

Some people find they gain weight because they are not as active as before. Also, some treatments used to treat MS, such as steroids, can cause you to gain weight. And, just as stress, anxiety, and depression can lead to weight loss, they can also lead to weight gain if you are a comfort eater.

“My concern with this study is that someone with MS would see the results and embark on a super-restrictive fad diet that could cause more harm than good,” says Caroline Thomason, RD, CDCES, a dietician who specializes in helping women stop dieting and feel better. “I currently treat folks with MS as a dietician. They often come to me initially with goals of weight loss. However, we often uncover that they struggle with severe fatigue, symptoms of burn-out, and big energy swings that affect their quality of life.”

“My clients with MS are more motivated to feel better than to lose a few pounds. When we first address their fatigue and low energy swings by creating healthy behaviors around food, exercise, and stress management,” Thomason continues, “we notice that weight loss might be a whole lot easier.”