There seems to be a lot of pseudo-science around intermittent fasting.
In particular I've heard people say things like "You can take black coffee", or "You can have sugar-free lemonade with no calories", or "As long as you don't consume more than 5 calories (or some other small number) your body remains in a fasted state".
Yet I've heard in reality you can basically only consume water and nothing else during your fast in order to not break the fasted state.
> Yet I've heard in reality you can basically only consume water and nothing else during your fast in order to not break the fasted state
I don’t think that’s true. AFAIK main thing is to not stimulate insulin production so while many sweeteners might break the state lots of things have effectively no insulin response (for example pure coffee).
Black coffee shouldn’t have calories, but it apparently does trigger metabolic responses in the brain, gut and liver.
Most people debating things like coffee, tea, lemon, even fish oil (which definitely has calories) have lost the forest for the trees, and they often can’t explain why they are fasting in the first place or their goals.
Unless you induce diarrhea, there’s food residues in the gut which keep adding to your energy bottomline for up to a few days. It’s unlikely that having a coffee or a supplement has a noticeable impact on your fasted state during intermittent fasting (when fasting 3+ days, things are different). To be sure, one could just measure serum insulin and ketone levels. Coffee will raise blood sugar, but it’s also lipolytic, so it’s both „bad“ and beneficial.
Nitpicking perhaps, but there's definitely measurable food energy in black coffee. A small mug of paper-filtered might be <1 kcal, but a double espresso might be 5+.
Anecdatally, on OMAD for 6 months (23h daily fast), with just espresso in the morning, and one meal late in the day, net have lost about 30 lbs. The weight loss slows down as your metabolism adapts. It is a way to get my total caloric intake down, as I just enjoyed eating too much and having to exercise discipline 3x+ a day is a losing battle. Out of sight, out of mind, etc.
Any perception of new mental clarity comes from how I relate to hunger, which I can mentally translate to a kind of excitement, similar to what some people can also do with fear. The clarity could easily be attributed to attitude and a choice that mitigates suffering. There probably isn't nutritional magic involved.
Yes, if all of this is just a way to get me to eat fewer calories, and that's all that's really happening, so be it. I've had several people scold me saying "You know you're just losing weight because of the calories, right?" and I'm like, so? Great!
I can't diet. Been trying that all my life and it's never going to happen. It's uncomfortable and socially inconvenient to be constantly weighing my food and passing up dinner invitations and never feeling satisfied. So I just don't eat a couple days a week and then forget about the rest.
Not a scientist, but I think this is one of those highly individual things.
Some people can drink X and stay in ketosis. Others can't.
This makes scientific studies on ketosis a pain to do, because we don't know whether something works at all or is it just due to individual differences.
My guess is that this is due to gut/intestine flora, but that stuff is still a complete mystery. Maybe we'll figure some of it out this decade.
In particular I've heard people say things like "You can take black coffee", or "You can have sugar-free lemonade with no calories", or "As long as you don't consume more than 5 calories (or some other small number) your body remains in a fasted state".
Yet I've heard in reality you can basically only consume water and nothing else during your fast in order to not break the fasted state.