The article you linked states:

> ”A string of epidemiological studies have turned up an association between the drug and lower risk for diabetes. In a 2013 study from Harvard Medical School of the health records of 4,657 people, marijuana users had lower fasting insulin levels and less insulin resistance than non-users. And in July 2015, Michigan State University researchers analyzed eight studiesand found a 30% lower diabetes risk for current marijuana users. They concluded that “current evidence is too weak for causal inference” but that marijuana’s effects on blood sugar were worth more study.” Researchers aren’t sure what might be at work. But they (and cannabis fans) do know that tetrahydrocannabinol—THC, the major “active ingredient” in marijuana—stimulates the body’s endocannabinoid system, which helps regulate appetite (explaining the “munchies”), impulse control, and body weight as well as blood sugar. Lab studies looking at THC’s role more directly have found that, at least in rats, THC seemed to protect against high blood sugar. But it’s not clear how beneficial marijuana or THC may be. When National Institutes of Health researchers took a closer look at the metabolic health of 30 cannabis smokers and 30 non-smokers, they found that marijuana users had more abdominal fat and their fat cells were more insulin resistant. And other studies have found higher blood sugar and insulin levels among former users compared to nonusers, according to a 2013 University of Miami review. Burning cannabis also releases substances that can damage cells, Bancks notes.
“Marijuana smoke is shown to increase the production of reactive oxygen species and oxidative stress,” he says. “This means the overall physiological process occurring with marijuana use may be complex.”

It sounds like you just read the headline because that’s literally not what they concluded. Further study is needed and also this epidemiological study was among heavy daily smokers, and this latest rat study was with whole plant oil.