Earlier quoted context omitted.
One drug advertisement I’ve seen on Pinterest lately says “diet and exercise can’t treat diabetes” which may be true of type 1 diabetes, but last time I checked 90% of the diabetes in the US is type 2 and diet improvements should absolutely be the first line intervention.
Diet and exercise are extremely effective in treating type 1 diabetes. But some exogenous insulin (and other medications) are usually still required. For type 2 diabetes, research had shown that many patients can put the condition into remission through lifestyle changes alone. Nutritional ketosis is very effective in reversing insulin resistance. https://www.virtahealth.com/research
Edit: Since I can't reply to another one of your posts below, I'm going to respond here. There's a "honeymoon period" after the initial symptoms of type 1 appear that yes you will still produce some insulin, for most patients it's about a year, but after that, no insulin is produced.
Zero-carb isn't a realistic long term solution. My son was diagnosed at 18 months of age. Feeding him nothing but bacon, steak and chicken is not particularly good idea for a toddler or growing child.