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The surgical community objects to the characterization of bariatric surgery as merely internal jaw wiring, cutting into healthy organs just to discipline people’s behavior. They’ve gone as far as to rename it “metabolic surgery,” suggesting the anatomical rearrangements cause changes in digestive hormones that offer unique physiological benefits. As evidence, they point to the remarkable remission rates for type 2 diabetes.
After bariatric surgery, about 50 percent of obese diabetics and 75 percent of super-obese diabetics go into remission, meaning they have normal blood sugars on a regular diet off all diabetes medications. The normalization in blood sugars can happen within literally days after the surgery. And then fifteen years after the surgery, 30 percent may remain free from their diabetes (compared to a 7 percent cure rate in a nonsurgical control group). Are we sure it was the surgery, though?
One of the most challenging parts of bariatric surgery is lifting the liver. Since obese individuals tend to have such large fatty livers, this can be tricky, risking liver injury and bleeding. Enlarged livers are one of the most common reasons less invasive laparoscopic surgery turns into to fully invasive open surgery, leaving the patient with a large full-belly scar, and increased risk of wound infections, complications, and recovery time. But lose even just 5 percent of your body weight, and your fatty liver may shrink by 10 percent. That’s why those awaiting bariatric surgery are put on a diet. Then, after surgery, patients are typically placed on an extremely low-calorie liquid diet for weeks. Could their improvement in blood sugars just be from the calorie restriction, rather than some sort of surgical metabolic magic? Researchers decided to put it to the test.
At a bariatric surgery clinic at the University of Texas, patients with type 2 diabetes scheduled for a gastric bypass volunteered to first undergo an identical period of calorie restriction, but without the surgery. They were placed in the hospital and put on the same diet they would be on immediately before and after the surgery for ten days, averaging less than 500 calories a day to mimic the surgical situation. Then, the researchers waited a few months so the patients would gain the weight back and, then put them through the actual surgery, matched day-for-day to the diets they were on before. So, the same patients and the same diets, just with or without the actual surgery.
If there was some sort of metabolic benefit to the anatomical rearrangement, they would have done better after the actual surgery, but in some ways they actually did worse. The calorie restriction alone resulted in similar improvements in blood sugar, pancreatic function, and insulin sensitivity, but several measures of diabetic control improved significantly more without the surgery. So, the surgery seemed to put them at a metabolic disadvantage.
The calorie restriction works by first mobilizing fat out of the liver. Type 2 diabetes is thought to be caused by fat building up in the liver, and then spilling over into the pancreas. Everyone may have a “personal fat threshold” for the safe storage of excess fat. When that limit is exceeded, fat gets deposited in the liver, where it causes insulin resistance. The liver attempts to offload some of the fat (in the form of a fat transport molecule called VLDL), which then gets stuck in the pancreas, and can kill off the cells that produce insulin. By the time diabetes is diagnosed, half of our insulin-producing cells may have been destroyed. Put people on a low-calorie diet, though, and this entire process can be reversed.
A large enough negative calorie balance can cause a profound drop in liver fat sufficient to resurrect liver insulin sensitivity within seven days. Keep it up, and the liver stops spitting out fat enough to help normalize pancreatic fat levels and function within just eight weeks. Once you drop below your personal fat threshold, you should then be able to resume normal intake, and still keep your diabetes at bay. The bottom line is that type 2 diabetes is reversible with weight loss, if you catch it early enough.
Lose more than 30 pounds, and nearly 90 percent of those who have had type 2 diabetes for less than four years can achieve remission, whereas it may only be reversible in 50 percent of whose who’ve lived with the disease for longer than eight years. That’s losing weight with diet alone, though. The remission numbers for diabetics losing even more than twice as much weight with bariatric surgery may only be around 75 percent and 40 percent, respectively.
Losing weight without resorting to surgery may offer other benefits as well. Diabetics losing weight with diet alone can significantly improve markers of systemic inflammation, such as tumor necrosis factor, whereas levels significantly worsened when about the same amount of weight was lost from a gastric bypass.
What about diabetic complications? One of the reasons we don’t want diabetes is that we don’t want to go blind, and we don’t want to have to go on dialysis. Reversing diabetes with bariatric surgery can improve kidney function but, surprisingly, it may not prevent the appearance or progression of diabetic vision loss. Perhaps because bariatric surgery affects diet quantity, but not necessarily diet quality.
This reminds me of a famous study published in the New England Journal of Medicine that randomized thousands of diabetics to an intensive lifestyle program that focused on weight loss. Ten years in, the study was stopped prematurely because the diabetics weren’t living any longer or having any fewer heart attacks. This may be because they remained on the same heart-clogging diet, but just in smaller portions.
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