Intermittent fasting is exactly what it sounds like: periodically going without food for many hours (16-24 is typical) for health benefits. There are many different fasting schedules, with fancy names like “16+8” or “Leangains” (16 hour fast followed by an 8-hour eating period, daily), “Bulletproof” (drink butter coffee instead of breakfast) and “alternate day fasting” (umm…). There are also a lot of different benefits ascribed to intermittent fasting: losing weight, increasing longevity (approaching LEV), stabilising blood-glucose levels and others.
At it's simplest, it seems like intermittent fasting could be a good way to limit consumed calories, and therefore lose weight (or, rather, body fat). That's why I'm experimenting with it, anyway1.
Your body is in the fed state when it is digesting and absorbing food. Typically, the fed state starts when you begin eating and lasts for three to five hours as your body digests and absorbs the food you just ate. When you are in the fed state, it’s very hard for your body to burn fat because your insulin levels are high.
After that timespan, your body goes into what is known as the post–absorptive state, which is just a fancy way of saying that your body isn’t processing a meal. The post–absorptive state lasts until 8 to 12 hours after your last meal, which is when you enter the fasted state. It is much easier for you body to burn fat in the fasted state because your insulin levels are low.
When you’re in the fasted state your body can burn fat that has been inaccessible during the fed state.
So, just as with a ketogenic diet, when there's not enough glucose in your system, your body switches to converting fat to ketones. Thinking about this logically, this while be more efficient when fully keto-adapted – so intermittent fasting + keto could be the winning combination for shredding fat!
Other potential benefits include:
- A simple daily meal plan
- Cost savings for food
- A simpler daily meal plan (one less meal to make)
- Calorific reduction increases longevity (see Immortality)
- It may reduce the risk of cancer