Depending on what you read – bodybuilding or mainstream literature – you’ll hear that insulin is great and that it’s the most anabolic hormone in the body – the key to getting big. Or, you may read that insulin is a demon – a stumbling block to fat loss and the single thing that makes you fat and ruins your health.
So which is right? Both actually. That’s because insulin is somewhat of a schizophrenic hormone.
On one hand, when food is consumed insulin is secreted, and that insulin is responsible for pushing nutrients to respective targets.
Then again, insulin can also create fat, if necessary, or at the least, inhibit fat loss.
So rather than looking at insulin as “good” or “bad” it may be better to think of it as a generalized storage hormone. What it does or does not do depends on many factors.
Both carbs and protein can elevate insulin, contrary to popular belief, so when insulin is elevated, it pushes nutrients into cells. So far so good, right? Insulin stimulates glycogen storage in the liver, and enhances glycogen storage in skeletal muscle – all good. It also decreases protein breakdown and that’s important to retaining hard-earned mass.
But in the negative column, insulin is also involved in fat storage because it activates an enzyme called lipoprotein lipase which is involved in breaking fatty acids off for storage.
Insulin also dramatically inhibits lipolysis (fat mobilization) from fat cells. Even fasting insulin levels may inhibit lipolysis by up to 50 percent. That means that even small increases in insulin beyond that would, in effect, turn off lipolysis completely.
Some interpret this as meaning that eating carbs means zero fat loss – that it is impossible.
Here’s the truth:
After you eat a meal (post-prandial phase of insulin) nutrients are being absorbed and digested from the gut and released into the bloodstream. A myriad of hormones are released and the body is in an anabolic state.
Eventually what you’ve eaten has all been digested, absorbed and either burned for energy or stored in various tissues (post-absorptive phase of insulin). At this point, hormone levels change and the body shifts to a catabolic state.
Over the course of a single day, the body shifts between the post-prandial and post-absorptive phases, and the body starts to draw on stored nutrients (hopefully stored fat in fat cells).
What really matters?
Some say choosing lower glycemic carbs matters a great deal in terms of whether insulin actually produces fat, or creates a purely anabolic response.
In addition, adding protein to carbs has been known to lower the GI for a couple of decades. However, it’s also been established that adding protein to carbs increases the insulin response. So where do you go from here?
Well, surprisingly, here’s what happens:
By eating a diet of protein and carbs, the carbs in the meal will increase insulin, while protein lowers blood glucose levels gives a lower effective GI.
Conversely, eating more protein and less carbs increases the insulin response to carbs. Go figure.
Now what about glycemic index? Well, an eye on lower-GI foods won’t indicate a true insulin response anyway. If it does it appears that low-GI foods may be generating a faster initial insulin response in the first place. Yet, none of that seems to impact on fuel utilization, so it’s a transient reading with no rooting in significance.
So, if you were to intake equal carbohydrate grams of white rice and brown rice, would you get the same insulin response?
Certainly any tiny differences in GI between brown and white rice are going to be utterly irrelevant in most cases – that is a fact.
Here’s the real truth: Insulin sensitivity in a particular individual certainly interacts with diet – those who are insulin resistant (who show early insulin response to food intake) seem to get superior results from a lower GI/lower-carbohydrate diet. Those with high insulin sensitivity show great results on a carb-based diet.
But in the end, it’s oxidative types of bodies – fast or slow oxidation – and other lifestyle and habits that most affect fat loss and gain. Consistency is key and insulin, it turns out, is not as great a culprit as most think.