Retrospective #475: The “Fast Mimicking” Diet

A WebMD Health article on the Fast Mimicking Diet (FMD), written awhile back for a “consumer audience,” was, I thought, a little too “thin” on substance. The paper that WebMD referenced in Cell, however, was a little too “thick.” Still, it was interesting, so I wrote about it here in #382, “Can fasting ‘wake-up’ the pancreas?”

Still, my editor thought I could do better, so she sent me this BBC piece, “Behind the Headlines – Health News from NHS Choices.” This time the porridge was neither “too thin” nor “too thick.” I thought it was just right!

The BBC lede jumps right to the conclusion: “‘The pancreas can be triggered to regenerate itself through a type of fasting diet, say US researchers.” Now, that’s an inviting prospect! Here are key excerpts, for your elucidation:

“Mice were fed for four days on a low-calorie, low-protein and low-carbohydrate but high-fat diet, receiving half their normal daily calorie intake on day one, followed by three days of 10% of their normal calorie intake.”

“Researchers repeated this fast on three occasions with 10 days of re-feeding on their usual high-carbohydrate diet in between to ensure they regained their body weight before the next fasting cycle.”

“They then examined the pancreas. They found, in mice modeled to have both type 1 and type 2 diabetes, insulin production was restored, insulin resistance was reduced, and beta cells could be regenerated.”

“Researchers also recruited healthy human adult volunteers without a history of diabetes, who underwent three cycles of a similar four-day fasting regimen. Their blood samples were applied to the cultured pancreatic human cells. The results in the human cell samples suggested similar findings to those seen in mice.”

The BBC summed it up: “The researchers concluded that, ‘These results indicate that an FMD promotes the reprogramming of pancreatic cells to restore insulin generation in islets from T1D patients and reverse both T1D and T2D phenotypes in mouse models.’” “This is good science,” a professor at Cambridge commented.

The Fast Mimicking Diet (FMD) employed in the study and reported on in Cell was conducted at the University of Southern California (USC) and the Koch Institute at MIT, plus in Italy. It was funded by grants from the US National Institutes of Health and the US National Institute on Aging. It was high fat, low carb, low protein and, okay, very low calorie, especially in the last 3 of the 4 days. In that sense, the FMD “mimics” a “water-only” fast; that is, the biomarkers had the same physiological effects on the body as the more extreme “water only” fast.

The FMD is a way to eat that tricks the body into thinking that a person is fasting. The 3 salient biomarkers that the body produces are 1) lower levels of IGF-1, a hormone with a molecular structure similar to insulin, 2) lower levels of glucose and 3) an increase in ketone bodies.  The hypothesis is that a more extreme “water-only” fast would produce the same effects, but is unnecessary if you’re unwilling to go there, yet.

The effect of the HIGH FAT, LOW CARB and LOW PROTEIN FMD used in the USC/MIT study on mice and men was to “reboot” the pancreas to help the insulin-producing cells repair themselves and start producing the hormone (insulin) again. The study in Cell said, “During periods of fasting, the cells go into ‘standby’ mode. When feeding begins again, new cells are produced that have the potential to become insulin-producing.”

From an evolutionary standpoint, the ability of animals to survive food deprivation is an adaptive response accompanied by the atrophy of many tissues to minimize energy expenditure. Thus periodic cycles of fasting, leading to the oxidation of pancreatic fat cells, the removal of impaired tissue (autophagy) and the death of other cells by apoptosis (pre-programmed death), “induced by the stepwise expression of certain genes,” are regulators of cell metabolism which enable the pancreas to reprogram itself to restore insulin production and regenerate stem cells similar to those observed during pancreatic development.

Read that last paragraph through again, and if you get it, ask yourself, might a Fast Mimicking Diet be worth a try?