Chronic fatigue syndrome (CFS) affects 2.5 million Americans, often leaving them unable to think or move. Many believe the disease is purely psychological, but researchers have discovered something that might change that: a unique decline in cell waste in CFS-affected blood, which also happens in hibernating animals and people with extreme caloric restriction, Pacific Standard reports. The researchers looked at 612 different metabolites—cell waste—in the blood of 45 CFS patients, and found that 80% of them were low compared with nonaffected blood, as they report in the Proceedings of the National Academy of Sciences. In this way, they could correctly identify CFS patients with 95% accuracy. The researchers say this is a huge leap toward better treatment and diagnosis in the disease, which has only been identifiable by symptoms in the past.