I work for a health science company and am a bio major at college, so the information provided is how the scientists, doctors, and professors that I try to learn from.
Type 2 diabetes is defined as a metabolic disorder that is characterized by high blood glucose in the context of insulin resistance (body cells do not appropriately respond when insulin is present).
With high-glycemic carbs, that results in at first, a very quick rise in blood sugar. Insulin is then released at a very quick rate to counteract the sugar in the blood and transport them into cells. Whatever is not needed by the cell, is converted into storage as fat by the liver. Sugar actually dips below baseline levels before it is adjusted properly.
These constant peaks and dips (caused by increased surges of sugar in the body), leading to high surges of insulin over a long period of time (we’re talking years here), is what tends to desensitize the GLUT transporters to insulin that transport glucose from body to cell. High glycemic carbs (ie simple carbs in rice, pasta, fruits, sweets, etc) are digested very quickly, while low-glycemic carbs (whole grain foods, vegetables, beans) are digested slower, leading to a slower release of sugar into bloodstream → insulin release is less and not in excess
This is also why waist measurement is sometimes used as a diagnosis of pre-diabetes and diabetes. The increased abdominal fat shows correlation with insulin sensitivity.
Think of it as pouring water into a glass. High glycemic: water is being poured so fast that there is overflow, and the spillage is “extra” → converted to fat
Low-glycemic: water poured at a slower rate, no spillage
Obviously, this is also determined by how much you are consuming at one time, not just what type. This leads to something called glycemic load, which is a measure of glycemic response based on the amount of carbs eaten per grams.
So it all really comes down to timing. High glycemic carbs are beneficial for post workout (whether it be lifting or simply cardio) to go from a catabolic state to an anabolic state, and also to refill glycogen stores. The muscles are become sensitive to glucose, and don’t often even need insulin as a transporter to intake glucose inside the cell. Also, research shows that exercise helps sensitize the receptors as it is. Again, goal is to not consume in excess and consume in a timely manner. This is why Surge was created. Berardi also wrote a few articles based on the research that supports it and his conclusions about it. Very good read.
However, if you eat high glycemic carbs just at rest, then the primitive human body will want to use what it needs, and store the rest as fat. Our nutrition has changed so much in the last 200 years, yet evolution is not able to accomodate that pace. Our body still thinks we’re hunters and gatherers. So in my opinion, and I think others may agree, if your intake of it while bulking was in a timely manner, than it should be fine. Also, you were bulking while training for your rowing team, so your body definitely needed as much energy it could get! Congrats with your gains, 35 pounds in 3 months is definitely worth praising. I did 20 pounds in 4 months, so more power to ya. Hope all of this helps, and clears up some questions.