We already have plenty of evidence, of course, that elevated blood sugar is unhealthy. People with hyperglycemia tend to be overweight and face greater long-term risks for heart disease and Type 2 diabetes, even if, in the early stages, their condition does not meet the criteria for those diseases.
They also tend to be out of shape. In epidemiological studies, people with elevated blood sugar often also have low aerobic fitness.
Taken as a whole, these results in mice and people suggest that “constantly bathing your tissues in sugar is just not a good idea” and could undercut any subsequent benefits from exercise, says [researcher] Sarah Lessard.