Insulin is a hormone that is released when carbohydrates, i.e. sugars are present in the blood. It collects and allocates the sugar for immediate energy requirements, brings a part into muscles and the liver (if they aren’t already full) and converts the rest into fat and stores it. It also stores dietary fats but they don’t trigger its release.
Insulin is the hormone that triggers fat gain by making the body create and store fat. It puts your body into fat-storing mode, instead of fat-burning mode for energy.
But its effects, as it is with all hormones, depend upon your activities and dieting.
This doesn’t mean you don’t need insulin. It must exist in the body and perform its functions. But if you often consume carbs, you invite it to be frequently secreted. High insulin means stop to burning excess fat. It also means many unwanted health conditions, now or in the future. And frequent high blood sugar means frequent suppression of HGH. This deprives you of the possible progress with your weight training too.
All carbs are not same in triggering insulin. Fast carbs as sugar, bread, etc., trigger fast secretion of this hormone. Slow carbs cause slower secretion – beans, lentils, peas, sweet potatoes. (“Fast” and “slow” pertains to the speed with which carbs are broken down in body. Greater speed = greater response or this hormone.)
Fruits contain sugar, but if you consume them whole (not juiced) and not in great amounts, they won’t cause great insulin response. They contain dietary fiber which is actually the most complex carb. Fiber is not absorbed in the body and is disposed of, and so it does not have caloric value. Fiber slows down the sugar breakdown and thus causes lower insulin response. Eat your fruit whole.
Nevertheless, this subdivision of slow and fast carbs doesn’t mean that slow carbs don’t make you fat and don’t reduce growth hormone.
As you take carbs during the day, you go into a state in which the body has as less a reason to use fats as a source i.e fuel for energy.
But if for example, you take 40 grams fast carbs at once, you’ll stop the fat burning for energy, because well, you have fresh, ready sugary energy.
So, dividing carbs into fast and slow (simple and complex) has some value if you don’t go over 20-40 grams a day. As you go over 40 grams, it matters less and less if it’s slow or fast carbs.Read about the other hormones