All our studies have shown evidence that BCAAs improve glucose metabolism. Probably by activating SIRT1 and also increasing mitochondrial biogenesis.
It causes a very small transient insulin release. Big deal. This is the problem with internet PhDs and guys writing articles who really don't understand metabolism. They would have you believe that any insulin release anywhere in any amount will cause all fat burning to completely stop and it will cause you to be insulin resistance. What a load of crap. Metabolism doesn't have 'on' or 'off' switches. Everything is running all the time; the emphasis just changes. Don't think of metabolism as flipping an on or off switch. Think of it as dimmer switches. You can brighten or darken without ever turning it completely off or on full blast.
There are 2 kinds of insulin release (ie biphasic). The first is a dumping of stored insulin. This is transient and induces a small rise for about 15 minutes. After that any remaining glucose is disposed by insulin production in the pancreas. The production of postprandial insulin is what causes the large insulin response... it is the second phase.
BCAA supplementation ONLY induces the first phase of insulin release. It does not cause long term increase in insulin. It causes a small bump for the first 15 minutes then it's done. Hardly enough to make you insulin resistant or blunt fat burning.