Intermittent fasting comes in a few different forms. Let’s discuss the science. One type of intermittent fasting is called alternate day fasting. In this type of dieting people will skip a day of eating food. On the days that they are not fasting, they typically eat what they want in test subjects this is called eating ad libitum. In some other types of intermittent fasting people only eat during a window of time during a day. For example setting an 8 hour block of the day and then not eating the other 16 hours.  Other versions involve drastic reductions (60-75%) in your typical caloric consumption on pseudo fasting days. Alternate day feeding in its purest form the diet does not actually decrease the amount of calories consumed but rather the frequency of meal ingestion. As far as the science goes there is a pretty good amount of data from animal studies. The human data is a bit lacking and many of the studies done unfortunately lack control groups.Sometimes calories are still decreased in the human studies causing a confounding in which we cannot tell if effects on the body are due to fasting or due to caloric restriction.

Studies in Animals

Studies of intermittent fasting in animals has been profound showing delayed onset and progression in brain diseases such as alzheimer’s, parkinson’s, and huntington’s disease. Studies have also shown decreases in blood sugar and lower risk of diabetes. Heart attack damage is less and unhealthy changes in the heart after a heart attack are also decreased in animals under an intermittent fasting diet. Animals tend to have a lower heart rate and decreased blood pressure and cholesterol levels. One are that has been studied in animals and not at all in humans is cancer during intermittent fasting. Animals studies have shown that those with cancer live longer when intermittent fasting and the risk of lymphoma is lower.

Studies in Humans

The data in humans is a bit less extensive and also less impressive. Psychology journals have published that humans during intermittent fasting have increased alertness and arousal. Our daily blood sugar levels do not become much lower although some studies have showed less insulin resistance leading to a possible lower risk of diabetes and a slightly higher HDL (good cholesterol), which can be cardioprotective. Diets as we know are very difficult to adhere to. A study comparing traditional dieting to intermittent fasting found both groups to lose weight and fat at the 2 month mark. When those groups were looked at again at the 6 month point the alternate daily feeding group had had better results.

The studies in animals are very interesting and it will be cool to see what else we find in human studies. At this point it is tough to make conclusions on if it’s worth the effort to adhere to an alternate day feeding diet. I am hopeful that the animal research will translate over to results in humans in the future research studies.

Sources:

1. Alternate-day fasting and chronic disease prevention: a review of human and animal trials
2. Impact of intermittent fasting on health and disease processes.
3. Intermittent fasting does not affect whole-body glucose, lipid, or protein metabolism
4. Effect of intermittent fasting and refeeding on insulin action in healthy men
5. Caloric restriction and intermittent fasting: Two potential diets for successful brain aging
6. Intermittent fasting and caloric restriction ameliorate age-related behavioral deficits in the triple-transgenic mouse model of Alzheimer’s disease
7. Beneficial effects of intermittent fasting and caloric restriction on the cardiovascular and cerebrovascular systems
8. Intermittent fasting dissociates beneficial effects of dietary restriction on glucose metabolism and neuronal resistance to injury from calorie intake