Mayo Clinic showed that moderate strength training had a 32 percent impact on diabetes: https://www.mayoclinicproceedings.org/article/S0025-6196(18)30789-4/fulltext
Meanwhile, insulin can and often does worsen the disease: https://www.bmj.com/content/349/bmj.g4335
Metformin has scant supporting evidence to show it can slow or reverse the disease: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6520897/
And neither insulin nor metformin have the ability to affect the underlying cause of diabetes: https://www.diabetes.co.uk/news/2018/jul/metformin-and-insulin-ineffective-in-improving-beta-cell-function-in-kids-with-type-2-diabetes-96767104.html
The cause of type 2 diabetes is cell receptor degradation. T2 diabetes simply means receptors don’t listen to energy transfer signals. Only strength training directly and abruptly reverses this, affecting cell receptor upregulation. In clinical trials, it is repeatedly superior at improving glucose responses: https://www.sciencedirect.com/science/article/abs/pii/S0167527313009212 .
When we contract skeletal muscle intensely, we enliven glucose transporters, which is a DIRECT and IMMEDIATE counter against the fundamental cause of diabetes. Lifting weights is the biochemical opposite of diabetes. A weight which can only be lifted for 8 reps, let’s say, is more INTENSE than a weight which can be lifted 12 times. This is the exercise science definition of “intensity”. A weight which can only be lifted 12 times is more intense than one which can be lifted 20 times. An exercise which can be done for hundreds or thousands of reps (ie - walking, running, cycling, group ex, light weights), therefore, is not intense and doesn’t exert a powerful influence on cell receptors to oppose diabetes.
But even moderate/higher intensity walks (contrasted against slow walk/sedentary) improve insulin sensitivity for up to 16 hours afterward: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3680825/ . Indirectly, cell receptors also upregulate through extreme dietary restriction to cause major weight loss.
The clinical proof for diabetes reversal involves strength training, regular activity AND extreme caloric restriction: https://pubmed.ncbi.nlm.nih.gov/31168922/.
Participants were free of diabetes two years later: https://diabetes.diabetesjournals.org/content/68/Supplement_1/66-OR
Other studies have shown total reversal of diabetes AND NO NEED FOR ANY MEDICATIONS still maintained after 10 years: https://www.bmj.com/content/374/bmj.n1449