The phrase "altered levels" refers to changes or variations in a certain quantity or condition. It means that something has been modified, adjusted, or transformed from its original state or measurement. Full definition
One way this occurs is by altering levels of important hormones linked with appetite and eating behavior. (articles.mercola.com)
Among the many effects of physical activity, exercise generally reduces the amount of fat in the body and also alters levels of inflammation. (well.blogs.nytimes.com)
Plants contain dopamine, serotonin, and melatonin at concentrations high enough to actually alter levels in our bloodstream. (fullhealthsecrets.com)