UPDATE: I NO LONGER ENDORSE INTERMITTENT FASTING AS A WEIGHT LOSS TECHNIQUE. PLEASE SEE HERE.
Type 2 Diabetes is an incredibly damaging disease that causes a huge amount of damage to both life and to our national healthcare expenses. Diabetes is the seventh leading cause of death in the United States. It has annual costs of $245,000,000,000. This is a huge problem for our nation and for 29.1 million people. There was early on some evidence in rats and mice that intermittent fasting could help with insulin sensitivity and potentially with diabetes, and the question is whether or not that same effect is seen in humans.
First things first we need to briefly discuss how Type 2 Diabetes develops. (Remember I am not a doctor or medical professional) First of all we will discuss how insulin functions in a healthy individual and then how it is warped in a person who develops Type 2 diabetes.
- A person consumes foods that increase blood sugar (especially carbohydrates)
- The pancreas (specifically the beta islet cells) read the increase in blood glucose and release insulin.
- Your cells see the increase in insulin and take it as a signal to bring the glucose in the blood into the cell for energy
- Blood sugar levels fall to normal.
- A person consumes food (frequently or of the type that chronically raises blood sugar levels)
- The pancreas reads the chronically elevated levels and produces more and more insulin
- The cells gradually become ‘resistant’ to the signal of the insulin and it takes more and more insulin for them to bring in the gluocose.
- Pancreas produces more insulin in order to try to drive the glucose into the resistant cells
- The elevated insulin levels damage the pancreas’ ability to produce insulin (the beta islet cells)
- The body can no longer produce enough insulin to bring blood sugar to normal.
It seems pretty obvious from this description that if there was a way to make the cells sensitive to insulin again it could make a huge difference for those suffering from Type 2 Diabetes or pre-diabetes. There was some evidence in rats that certain variations of intermittent fasting were useful in increasing insulin sensitivity and this spurred a lot of interest in whether the same effect may exist in humans.
If it did exist what we would hope to see after a period of fasting is an increased ability for the body to take up glucose after a period of fasting. This study which was done in healthy men, showed a slight but statistically significant increase in glucose update in healthy men when insulin was infused after a period of 20h of fasting. This seems to suggest that there is a change in insulin sensitivity as a result of intermittent fasting. The other important thing to consider about this study is that it was done on healthy men, who we do not expect to have any existing insulin resistance. This to me at least suggests there may be a more dramatic increase in insulin sensitivity in people who have already developed some degree of insulin resistance. Furthermore, it was done in absence of caloric restriction (meaning in total they ate the same they normally did) suggesting that the effect can be attributed to the fasting. This study to me seems to suggest that intermittent fasting could have a similar effect in humans as in mice and rats in terms of its effect on insulin mechanisms.
This is important to note as other studies and meta-reviews have shown that IF is similar to normal calorie restriction (here). So that means there does seem to be a physiological advantage to intermittent fasting. Furthermore, even if there was not a difference vs. a normal calorie restricted diet, it could still be useful if it turns out that it is easier for a person to comply with an intermittent fasting diet.
The final note I want to make on this topic is to make it clear that this form of dieting does not seem to affect the actual metabolism, and instead seems to only affect sensitivity (here). This shows that if there is a benefit to people with intermittent fasting and its relationship to diabetes or insulin resistance, it primarily comes not from a metabolic shift, but from an increased sensitivity to insulin and the potential for weight loss.