Once upon a time, keto was the original “diabetes diet” prescribed to type 1 diabetes patients before the advent of insulin, as this would prolong their lives as it has less of an impact on blood sugar levels. More recently, Doctor Bernstein has popularized the keto diet for people living with diabetes in his book: Dr. Bernstein’s Diabetes Solution: The Complete Guide to Achieving Normal Blood Sugars

One study, published in the journal Nutrition & Metabolism, found a group of 28 people with type 2 diabetes overall lost about 6 percent of their body weight and lowered their blood glucose levels when they followed a keto diet for 16 weeks. The authors recommended individuals on this diet who have diabetes be under close medical supervision, and noted more research is needed on the diet’s long-term effects because the study was small and short term.
Without peer-reviewed clinical trials, many of the benefits remain anecdotal. For instance, Weiss himself has been on a low-carb high-fat (though not strictly ketogenic) diet for more than six months, and claims he does feel much better. But he’s clear about what he knows and what he doesn’t. He’s lost weight and his borderline pre-diabetes is gone.  
On a ketogenic diet, your entire body switches its fuel supply to run mostly on fat, burning fat 24-7. When insulin levels become very low, fat burning can increase dramatically. It becomes easier to access your fat stores to burn them off. This is great if you’re trying to lose weight, but there are also other less obvious benefits, such as less hunger and a steady supply of energy. This may help keep you alert and focused.