What does 'breaking a fast' actually mean?

I see a lot of questions on /r/fasting about whether a certain product breaks a fast. I learned that if it has calories, it breaks a fast. But what does the breaking of a fast actually mean? If I'm not mistaken, if you take in a few calories, you still reap the benefits for weight loss (you'll get a spike in blood sugar perhaps, but *calories in* are still less than *calories out*). Or are there other fat burning processes interrupted as well? And autophagy is halted. But does the autophagy process have such an on/off switch? How long does it take after a few calories to go into autophagy mode again?

Answer

It’s a simple question, with many complicated opinions and answers, isn’t it?

I would describe ‘break fast’ as either:
a. Eating to the point that you are full
b. Eating to the point that you are hungry

‘a’ is quite obvious, as if you eat until you’re full, you are obviously no longer fasting. ‘b’ on the other hand is subjective. For example, is it breaking a fast if you have 10 calories of electrolyte mix? Doubtful, as it is a small amount and shouldn’t spike your insulin.

What about 100 calories of toast? I would say this IS breaking your fast for multiple reasons. Firstly, that’s a significant portion of calories and will change your hormonal balance. Secondly, and related to the first point, this will in all likelihood make you HUNGRY.

Have you ever noticed it’s easier to not eat at all during a day, vs if you eat breakfast you are already hungry by lunch? That is because you have broken your fast.

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If your goal is weight loss.. 50-200 calories per day won’t really hurt you… but it will make it a LOT harder as you will be much more hungry.

Answer

Autophagy is not well understood at the moment and there are only educated guesses about it. A few years ago they thought black coffee would stop autophagy, now they say that black coffee not only doesn’t interfere with autophagy but actually enhances it. Apple cider vinegar is another question mark that they don’t know if it affects autophagy or not.

My guess is that autophagy is not a simple on/off switch and that it is instead a sloping curve dependent on what and how much you put into your body.

I’m pretty sure I’m seeing the effects of autophagy on myself since I started fasting. I have taken photos of myself over the last 6 months and have noticed that age spots have almost completely disappeared on certain parts of my body. I just saw that a few days ago and couldn’t believe it until I took high def pictures and zoomed in to get a good look.