Obesity and multiple sclerosis

Obesity and multiple sclerosis (MS) are closely linked, with evidence suggesting that excess body weight may increase the risk of developing MS and affect disease progression over time.

MS is a disease of the central nervous system, in which the immune system mistakenly attacks the brain and spinal cord, leading to inflammation and damage that disrupt nerve signaling.

According to the World Health Organization, overweight and obesity are defined as an excessive or abnormal fat accumulation that can pose health risks. These conditions are typically assessed using body mass index (BMI) — an estimate of a person’s body fat based on their height and weight — with a BMI of 25 or higher considered overweight, and 30 or higher classified as obese.

Both MS and obesity are becoming more common worldwide, and some scientists believe the rise in obesity is in part responsible for the increase in MS rates. While the exact mechanisms underlying this link are still being investigated, obesity’s effects on inflammatory responses are thought to play a major role.

Is obesity a risk factor for MS?

MS is thought to arise from a combination of genetic and environmental risk factors. Several studies have found the risk of MS with obesity is elevated, especially when obesity starts in childhood or adolescence.

A landmark 2021 study showed that genetic variants linked to a higher BMI were associated with a higher risk of MS. The data suggested that increases in BMI from being overweight to obese increased the risk of developing MS by 41%. More recent studies, including one published in 2025, have confirmed this relationship.

Evidence also shows childhood and adolescent obesity is strongly associated with an increased risk of MS in adulthood, and that lifestyle interventions for weight loss may not reverse that association. A higher BMI in early life may also be associated with an increased pediatric MS risk.

Does obesity influence MS symptoms and progression?

Beyond increasing the risk of developing MS, obesity may also influence how the disease progresses after diagnosis.

Research suggests people with MS who are obese tend to experience faster disease progression and greater disability compared with those at a healthy weight.

Some studies have also linked obesity to a higher rate of new lesions and higher relapse rates, especially in people with relapsing-remitting MS, though this link is not as clearly established.

Excess weight can also make certain MS symptoms more severe or harder to manage:

Pain and mobility issues: Carrying extra weight can strain muscles and joints, exacerbating pain and making it harder to move.

Fatigue: Chronic inflammation linked to obesity, along with the added effort required to move, can increase fatigue.

Bladder issues: Excess weight puts pressure on the pelvis, leading to involuntary urine leakage or other bladder issues.

Mood and cognition: Obesity-related inflammation may contribute to cognitive difficulties, while the combined effects of physical discomfort, fatigue, and social stigma can contribute to depression or low mood.

How obesity affects MS

The biological mechanisms linking obesity and MS are not yet fully understood, but scientists believe several factors may be involved.

Chronic inflammation: Obesity promotes persistent inflammation throughout the body. Fat cells release signaling molecules called adipokines which alter the immune response and promote inflammation in the brain and spinal cord.

Vitamin D deficiency: Fat tissue can trap vitamin D, making it less available for use in the body. Because low vitamin D levels are a well-established risk factor for MS, this may partially help explain the link between obesity and the disease.

Altered gut microbiota: Diet-induced obesity changes the balance of the gut microbiota, the collection of bacteria and other microbes that live in the digestive tract. These changes can influence immune function and contribute to disease onset and MS progression.
Metabolic changes: Obesity can disrupt how the body processes sugars and fats, leading to changes in metabolism that promote inflammation.
Reduced blood-brain-barrier integrity: Inflammation associated with obesity may weaken the blood-brain barrier, a protective membrane that separates the brain from the bloodstream. When this barrier becomes more permeable, immune cells can more easily enter the brain and spinal cord to cause damage.
Shared genetics: Some genetic variants appear to increase susceptibility to both obesity and MS, suggesting overlapping biological pathways.

MS and obesity research

Although a link between obesity and MS has been established, researchers are still working to better understand the biological mechanisms behind it.

Studies are also exploring how maintaining a healthy weight may affect MS onset, symptoms, and progression. Ongoing research is assessing the impact of different interventions, including:

Weight management strategies for living with MS

Obesity is a modifiable risk factor, meaning a person can make lifestyle changes to maintain a healthy weight and make living with MS easier.

Eating a well-balanced diet: Patients can work with a dietitian or nutritionist to create a well-balanced food plan that fits individual needs and activity levels, focusing on mindful eating and portion control.

Staying active: A regular exercise routine, tailored to each person’s abilities with guidance from a physiotherapist or occupational therapist, can support both weight control and symptom management.

Building a support system: Support from family, friends, or peers with MS can help patients stay motivated and make lifestyle changes more sustainable.

Managing weight can be particularly challenging with MS, as symptoms like fatigue or mobility issues, and sometimes medication side effects, may limit physical activity. Setting realistic, achievable goals is key.

People with MS should work closely with their multidisciplinary care team to develop a safe, individualized, and long-term strategy for maintaining a healthy weight.

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