I've always been a rather skinny guy, and things after my diabetes diagnosis had even worsened. (Did you know that glycemia affects our muscular mass? More infos here.) But, through an accurate exercise pattern and a well-studied meal plan, I've managed to obtain huge gains in muscular mass in a relatively short amount of time. Here's how!
First and foremost, during bodybuilding you will need to bulk whenever your body fat percentage reaches lower values than 10%. In order to effectively do it with diabetes, we have to focus on three fundamental points: exercise, alimentation and BG.
Exercise is without any doubt the most important aspect to focus on in order to put on muscular mass: to obtain gains, the frequency of strenght training recommended by most experts goes from 4 to 6 workouts per week, each with a duration of 45 to 90 minutes. In order to obtain a lean bulk and not an excessively fatty dirty bulk, some cardio should also be made: I do generally opt for the good old 10.000 steps per day, but in case you prefer intense cardio activity, 2 sessions of 30 minutes each per week should be enough. It is important not to exaggerate with cardio, as an excess of it might cancel the bulking gains obtained with so much dedication.
As for alimentation, bulking necessarily implies a calorific surplus, which has to exceed of about 300-500kcal your normal caloric requirements. Macros should be tracked carefully: during my bulking phase, I generally follow the 40-40-20 rule, which I found extremely beneficial both for muscular gains and for diabetes management: you basically have to cover at least 20% of your calorific intake with protein, another 40% with carbs and the remaining part with fats (in our case they cover an higher percentage than in non-diabetic people, as it would be difficult to mantain our BG pretty stable with an extremely huge amount of carbs). I suggest you visit this site for a clear definition of your alimentar needs (it's in Italian, but it is really intuitive and accurate!). Always remember that splicing your calorific intake into many meals is way more effective than only eating three extremely big repasts.
And now it is the moment for the aspect we need to be most careful about: glycemia. To promote muscular growth, it is fundamentl to mantain our blood glucose at stable and in-range levels most of the time, otherwise our muscular tissue would be directly affected. In order to do this, considering that we would be naturally helped by the growth of lean mass during our bulking phase, a brief walk after meals which are high in glycaemic index could be helpful, alongside with an increase in basal insulin doses if an unexpected rise in BG levels is observed overnight or many hours away from the meals. This suggestions are, needless to say, to be added to the ones reported in the Diabetes Management section, which are, at least for what concerns my personal experience, always valid.
Thank you for reading, and good luck with your bulking phase!