It's often called the most anabolic hormone of all... and it's not testosterone. It's insulin.
But insulin is a two-faced "frenemy." How your body handles insulin can drive both muscle gain andfat gain. If you want to manipulate insulin to your advantage, then you need to increase your insulin sensitivity i.e. become less insulin resistant. This will result in less body fat storage and the ability to build muscle easier, especially if you incorporate peri-workout nutrition tactics in this insulin-sensitive state.
A recent study showed that dietary supplementation an anthocyanin found in whole blueberries, called C3G, improved insulin sensitivity in insulin-resistant individuals. Basically, researchers gave fat (but non-diabetic) participants two blueberry smoothies per day for six weeks. At the end of the study, 67% showed a 10% or greater improvement in their insulin sensitivity.
Since more than half of the American population is predicted to have diabetes or be prediabetic by 2020 (which would amount to a gut-shot to the healthcare system) this is good news. For the physique-focused gym rat, eating blueberries or supplementing with blueberry concentrates could result in more muscle-building and less fat-building over time.
Adding fresh or frozen blueberries to a couple of protein shakes every day will help. Another option is to simply use Superfood, which contains freeze-dried organic blueberries with the same bioactivity as fresh.
Remember, insulin can be your friend or your enemy. It's up to you to tell it what to do. It looks like consuming blueberries is one way to do that.
Study: April J et al. Bioactives in Blueberries Improve Insulin Sensitivity in Obese, Insulin-Resistant Men and Women. J Nutr. 2010 Oct; 140(10):1764–1768.