Parkinson’s weight loss driven by burning fat instead of glucose
Metabolic shift triggers the use of backup fuel regardless of calorie intake
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- Parkinson's weight loss stems from a metabolic shift, burning fat instead of glucose, not just reduced calorie intake.
- Patients primarily lose body fat, not muscle, due to impaired glucose processing and mitochondrial dysfunction.
- Future interventions should target metabolic pathways, as increased calories alone may not prevent weight loss.
The weight loss commonly seen in Parkinson’s disease isn’t just about eating less. It’s about a fundamental shift in how the body fuels itself.
According to a new study, Parkinson’s patients primarily lose body fat, not muscle, because their bodies struggle to process glucose, a complex sugar the body normally relies on as its primary energy source. As a result, their bodies are forced to burn fat and protein as a “backup” energy source, especially those with lower body fat or with more advanced disease.
This discovery by Japanese researchers suggests that simply increasing calorie intake may not be enough to stop weight loss if the body’s primary energy pathway is disrupted.
“We clarified that it is not the muscle that is decreasing, but the fat,” Hirohisa Watanabe, PhD, professor at Fujita Health University, who led the study, said in a university press release. “This changes how we should think about weight loss in Parkinson’s disease.”
Although “future longitudinal studies … are needed to clarify these metabolic shifts,” researchers noted the results “highlight metabolic pathways as potential targets for interventions to mitigate weight loss in [Parkinson’s].”
The study, “Metabolic profiles associated with fat loss in Parkinson’s disease,” was published in the Journal of Neurology, Neurosurgery & Psychiatry.
Shifting the focus from calories to metabolism
Weight loss is a common nonmotor symptom of Parkinson’s that has been linked to disease progression and reduced life expectancy. It is often attributed to reduced food intake, increased energy use, or medication side effects. However, the underlying biological mechanisms remain poorly understood.
Parkinson’s is also characterized by mitochondrial dysfunction, the structures inside cells that generate energy. When these energy-producing systems are impaired, the body may struggle to efficiently use glucose and shift toward burning fat for fuel.
Similar metabolic shifts have been observed in other neurodegenerative diseases, such as Alzheimer’s disease and amyotrophic lateral sclerosis, but they have been less thoroughly studied in Parkinson’s.
To explore this, researchers enrolled 91 people with Parkinson’s and 47 healthy individuals of similar age and sex at Fujita Health University Hospital from July 2021 to October 2023.
They assessed body composition using a noninvasive method that allows separate measurement of fat and muscle mass. Blood samples were analyzed for metabolites — small molecules that reflect how the body produces energy, including markers of glucose metabolism, and fat breakdown.
Among patients, the mean age was 69.2, and symptoms began at age 62.4. On average, participants had been living with Parkinson’s for nearly seven years. Men and women were represented in similar proportions, and there were no significant differences in age or sex distribution between Parkinson’s and healthy individuals.
Compared with healthy participants, people with Parkinson’s had lower body weight and lower body mass index (BMI), a measure of body fat based on height and weight. This difference was driven primarily by a reduction in fat mass, whereas muscle mass did not differ significantly between groups. The proportion of participants with sarcopenia, an age-related loss of muscle mass and strength, was similar to that seen in the general older population.
Blood analyses revealed clear metabolic differences. Compared with healthy individuals, patients had lower levels of metabolites associated with glucose use. At the same time, they showed higher levels of ketone bodies, which are substances produced when the body burns fat for energy, along with other metabolites linked to fat and protein breakdown. This pattern suggests a shift away from glucose-based energy production toward alternative fuel sources.
Among people with Parkinson’s, lower BMI was associated with higher ketone levels. Higher ketone bodies were also observed in patients with more advanced disease, who tended to have lower BMI and fat mass. Together, these findings suggest that as Parkinson’s progresses, the body increasingly relies on fat breakdown to compensate for impaired glucose metabolism.
These metabolic shifts remained significant even after adjusting for nutritional status, meaning they were unlikely to be explained solely by reduced food intake.
“By elucidating the specific metabolic alterations linked to fat mass reduction in [Parkinson’s], this study provides potential biomarkers for detecting early metabolic imbalance,” the researchers wrote. “Clinically, assessing metabolic markers could help identify patients at higher risk of nutritional deterioration.”
They also added that such findings “underscore the need to consider broader metabolic pathways when developing dietary and therapeutic strategies for [Parkinson’s].”
