Obesity can exacerbate certain medical conditions, but it may help patients with amyotrophic lateral sclerosis (ALS), aka Lou Gehrig’s disease. In a retrospective study of more than 400 ALS patients, Massachusetts General Hospital (MGH) researchers found that those who were mildly obese survived longer than patients living at a normal weight. The study, which finds that survival is predicted by body mass index, not lipid levels, will appear in the journal Muscle & Nerve.
"We have long known that being underweight shortens survival for ALS patients, and several studies in an animal model have shown that weight gain is associated with increased survival," says Anne-Marie Wills, MD, MPH, of the MGH Neurology Clinical Trials Unit, senior author of the report.
"Our study was designed to investigate how cholesterol levels affect survival. We were surprised to find that body mass index or BMI – a measure of weight adjusted for height – made a large difference in survival. Patients with a BMI of 30 to 35, who would be considered mildly clinically obese, lived the longest; and patients who were overweight, with a BMI of 25 to 30, lived the second longest," says Wills.
During the course of the disease, ALS patients can lose even more weight than can be attributed to the loss of muscle mass caused by nerve destruction and related muscle inactivity. According to Mass. General, studies have shown that ALS patients burn more calories than would be expected from their limited physical activity, but the mechanism for this metabolic change is currently unknown.
A previous smaller study suggested that ALS patients with higher levels of low-density lipoprotein (LDL) relative to high-density lipoprotein (HDL) might live longer.
Depending on the particular clinical trial, survival data was available for one to two years after study initiation. While higher baseline cholesterol levels were associated with longer survival, that association disappeared when the results were controlled for BMI. The shortest survival rate was seen in malnourished or morbidly obese patients, but patients in the mildly obese range had the longest survival of any BMI group.
[Source: Massachusetts General Hospital]