First, the loss of fluids from excessive urination can lead to a low level of body fluids, which can make you weigh less. This is what often accounts for very rapid weight loss with new-onset diabetes.
Second, if insulin levels are too low for glucose metabolism, your body will switch to burning fat to maintain cellular metabolism, and burning fat can lead to weight loss (just what you’re trying to do at the gym, right?).
Third, the large amount of urine that is generated by high blood glucose is rich with glucose — sometimes in excess of 1,000 mg/dl. That glucose is full of calories, so when there are high levels of glucose in your urine, you’re literally peeing calories away as your body tries to jettison the excess glucose. If your high blood glucose level is a new development, you previously maintained a stable weight, and you make no change in your eating habits, you’ll lose weight as a consequence of high blood glucose.
Teenage girls with Type 1 diabetes have been known to manipulate this biological phenomenon via an eating disorder called diabulimia. They keep their weight low by keeping their blood glucose high, allowing them to eat more food while maintaining a lower body weight. But doing so comes at the price of life-threatening complications.
Your body’s cells aren’t the only inhabitants of the microscopic world that eat glucose: Many bacteria and yeasts do, too.
Urinary tract infections (UTIs) and yeast infections can occur in both men and women, but they are much more common among women, and they’re particularly common among women with diabetes. In fact, women with diabetes are two to three times more likely to have bacteria in their urine than women who don’t have diabetes.
Both bacteria and yeast thrive in warm, dark, moist places and feed on glucose. Chronic yeast infections are common in women with chronically high blood glucose. The cause may simply be a case of supply and demand: More glucose gives yeast more opportunities.
UTIs, on the other hand, are quite a bit more complicated, and high blood glucose contributes to them in several ways beyond providing glucose-rich urine for the bacteria to grow in. Long-term elevated blood glucose can lead to a number of complications, including neuropathy, or damage to nerve tissue, which can affect a wide variety of body systems. Neuropathy can affect the bladder’s ability to contract properly, causing incomplete emptying. This leaves behind residual pools of static urine in the bladder — the perfect growth culture for bacteria.
In addition, elevated glucose reduces blood circulation, which in turn reduces the ability of infection-fighting leukocytes (white blood cells) to get where they are needed in a timely manner in sufficient numbers to fight off infections. High blood glucose also reduces phagocytosis, the process leukocytes use to ingest bacteria.
Slow healing of cuts and wounds
High blood glucose greatly slows the healing of skin and soft-tissue infections because neutrophils, the most common type of leukocyte in the immune system’s arsenal, are particularly vulnerable to high levels of glucose. High blood glucose keeps the neutrophils from sticking to the endothelium, the inner lining of the blood vessels; disrupts chemotaxis, the body’s chemical signaling control system that directs neutrophils to the site of injuries or infections; and, as noted above, makes phagocytosis sluggish.
Another critical element of wound healing is a sufficient supply of oxygen, and the delivery of oxygen can be reduced by either peripheral neuropathy (nerve damage) or peripheral vascular disease (blood vessel disease) — both common conditions caused by or made worse by high blood glucose.