Intermittent Fasting is Beneficial in Humans

Evidence from the scientific community shows intermittent fasting to be beneficial in numerous species, including our own. The materials here discuss what I would call time restricted feeding rather than intermittent fasting. Restricting the hours that one eats during the day, but still otherwise eating ad libitum every day, can arguably be thought of as a mild form of intermittent fasting that doesn't rise to the level of, say, alternate day fasting or a quarterly five day implementation of the fasting mimicking diet. Nonetheless, there are benefits. It remains to be robustly determined in humans as to whether the benefits resulting from these milder forms of intermittent fasting are largely derived from a reduction in overall calories consumed or from undergoing periods of low calorie intake. Both have been shown to produce benefits in mice and rats, independently of one another.

Intermittent fasting diets fall generally into two categories: daily time-restricted feeding, which narrows eating times to 6-8 hours per day, and so-called 5:2 intermittent fasting, in which people limit themselves to one moderate-sized meal two days each week. An array of animal and some human studies have shown that alternating between times of fasting and eating supports cellular health, probably by triggering an age-old adaptation to periods of food scarcity called metabolic switching. Such a switch occurs when cells use up their stores of rapidly accessible, sugar-based fuel, and begin converting fat into energy in a slower metabolic process.

Studies have shown that this switch improves blood sugar regulation, increases resistance to stress, and suppresses inflammation for various periods of time. Because most Americans eat three meals plus snacks each day, they do not experience the switch, or the suggested benefits. Studies in both animals and people found intermittent fasting also decreased blood pressure, blood lipid levels, and resting heart rates. Evidence is also mounting that intermittent fasting can modify risk factors associated with obesity and diabetes. Two studies of 100 overweight women showed that those on the 5:2 intermittent fasting diet lost the same amount of weight as women who restricted calories, but did better on measures of insulin sensitivity and reduced belly fat than those in the calorie-reduction group.

More recently, preliminary studies suggest that intermittent fasting could benefit brain health too. A clinical trial found that 220 healthy, nonobese adults who maintained a calorie restricted diet for two years showed signs of improved memory in a battery of cognitive tests. While far more research needs to be done to prove any effects of intermittent fasting on learning and memory, if that proof is found, the fasting - or a pharmaceutical equivalent that mimics it - may offer interventions that can stave off neurodegeneration and dementia.



I'm practicing different regimes of intermittent fasting mainly to induce autophagy.
Is there any data available after how many hours of fasting autophagy is activated?

Posted by: Stephan at January 1st, 2020 2:44 PM

Technically, autophagy is always active. Sometimes much more. And sometimes it gets impeded to much. Different tissues or even cells might have different activity patterns.

If we take in consideration that the body has developed a lot of energy saving and efficiency features then we can make a few educated guesses.

As long as your boss sugar is high the body is in overdrive mode. No real need to save energy, can store the excess as fat.

If no food is coming then the local and leaver sugar depots can be used to maintain the blood sugar level above the hypoglycemia levels. At this point the cells have an incentive to ramp up autophagy. At least for short periods. Depending on your BMI and glucose depot stores it could start as soon as immediately or after a night sleep.
People practicing fasting for many days might tell that snorting less than x days is not bringing lasting benefits. But for sure the moment there body depletes the glucose depots it switches to keto mode. If the keto mode is due to fasting and not keto diets the body is actively scavenging resources and the autophagy she be quite active. Note also that it might take a longer people to "cleanup" a bloated cell. I cannot find easily interpret Ed data in how much and how long it takes

Posted by: Cuberat at January 1st, 2020 7:57 PM

One of the pieces of data I've been trying to figure out is whether intermittent fasting or caloric restriction is more beneficial. It seems like intermittent fasting is almost like a fad nowadays, but I see few studies comparing it to CR.

I'm not ready to jump on the intermittent fasting bandwagon just yet, as almost all of the studies involve overweight people. CR is simpler to understand - you just eat fewer calories.

Most importantly, I haven't read how intermittent fasting interacts with drugs and supplements. If I don't eat with the drugs and supplements I take, then I end up nauseated and vomiting. No study has reviewed what happens if you eat 50 calories in the middle of the "fast" period to avoid nausea when taking pills.

I suspect that by the time someone actually performs a study comparing CR, IF, and other interventions, the results will be obsolete because there will be drugs available that cause the same signals to be generated.

Posted by: Steve Sokolowski at January 2nd, 2020 11:17 AM

@stephan, I researched that question 10 years ago. There is far from a consensus on the answer. Probably because it is a complex process.The simple answer I found most credible was 16 hours. But surely that number will vary slightly based upon BOdy fat percentage and carb content of your diet and activity level.

Posted by: JohnD at January 2nd, 2020 12:51 PM

It seems to me that a hypothetical limit to the number of hours of daily fasting in time restricted feeding resulting in modifying risk factors associated with diabetes might be around 20 to 22 hours at most, since at about this point we are dealing with virtually one meal a day (OMAD) and its consequently increased glycemic load.

Posted by: BrianValerie at January 5th, 2020 3:24 PM
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