IGF1 is known as possibly the most anabolic hormone in the body, how ever not many are aware to its health benefits, especially pertaining insulin sensitivity. Modern western diet, as well as the feeding regimes of many bodybuilders creates an overburden on the pancreas due to the demand to cope with a surplus in calories (especially carbs and proteins, which raise sharply insulin levels), this leads with time to reduced insulin sensitivity, the constantly high insulin levels simply reduce the sensitivity of different tissues (mainly muscle and fat) to insulin.
There is also a common (dangerous) practice used by many bodybuilders to incorporate exogenous insulin to help and process these surpluses and try to force "extra" growth by this overfeeding, but this harms even more the insulin sensitivity and leads to insulin resistance syndrome.

IGF1 raises directly insulin sensitivity, and helps the body to process and use much more efficiently its own insulin

The work with IGF1 is simple and easy to monitor (IGF1-lr3is the preferred choice as it has the longest half life so most favorable metabolic effect ), the basic protocol is 20-30mcg before the main meal of the day, preferably post workout, and it may be used efficiently this way year round.

To take advantage over the full anabolic effect of the IGF1 higher dosages are required (50-150mcg a day), but then it's advised to cycle the usage in 4 weeks on/4 weeks off protocol

IGF1 really shines along with GH usage, they offer a synergistic anabolic and anti catabolic effects, but just like explained above they compliment each other very well metabolically, as GH raises directly the glucose levels (and with time this lowers insulin sensitivity), while IGF1 lowers the glucose levels to low healthy levels and restores insulin sensitivity