Intermittent fasting, which means going without food for some time, might have benefits for antiaging beyond simple calorie   restriction.

There are many different fasting regimens.

One common form involves a sixteen-hour fast (including sleep time) and an eight-hour “feeding window.”

Some people practice alternate-day fasting, in which they eat little to no food on one day, and on the next day, eating is unrestricted.

Animals fed every other day behave physiologically like calorie-restricted animals, even though they eat almost the same amount of food as fully-fed animals.

The animals that are fed every other day eat more on feeding days to compensate for their fasting days.

This finding casts some doubt on whether fewer calories are essential to the life span extension.

Although total calories are similar between calorie restriction and every-other-day fasting, the hormonal effects of fasting are very different.

During fasting, all the nutrient sensor pathways are engaged insulin and mTOR decrease while AMPK increases.

Other hormones, known as the counterregulatory hormones, increase.

These hormones include adrenaline, noradrenaline, and growth hormone.

The increase in counterregulatory hormones has the effect of increasing energy and maintaining basal metabolic rate.

These hormonal changes do not occur with simple chronic calorie reduction.

The calories might be the same, but the physiologic effect is not.

For example, reducing dietary fat reduces calories but not insulin or mTOR because the carbohydrate and protein intake may be unchanged.

Calorie-restricted (CR) animals are always hungry because of increased hunger hormone signalling.

Because hunger is such a fundamental instinct, it’s virtually impossible to ignore hunger over the long term; hunger dooms many weight-loss programs to failure.

Fasting, on the other hand, often paradoxically decreases food cravings and hunger.

Many patients note decreased hunger when using intermittent fasting for weight loss.

They often comment that they think their stomach shrank when, in reality, hunger signalling decreased.

Rats and mice placed on an every-other-day feeding/fasting regimen live longer than fully-fed animals.

This result occurs without necessarily decreasing body weight, depending on the particular species of animal used.


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