One person's field notes on confusing thirst for hunger, leaning on zero drinks through long fasts, and what coffee may have been doing.
A quick caveat before any of this. None of what follows is medical advice or a claim about how your body works. It's a set of things I noticed in myself over a long stretch of paying close attention, and the small habits I built around them. Your body may behave nothing like mine. Treat this as one person's field notes, not physiology.
With that said. For most of my life I never paid attention to drinking enough water. You assume the system is automatic: your body asks for liquid, you respond, done. Some water, some tea, a zero drink here and there. But somewhere along the way I noticed that in me, that mechanism doesn't run cleanly. I'm often thirsty, maybe under-hydrated, and the signal just doesn't arrive in a form I recognize.
My own theory, and I'll keep calling it a theory, is that I sometimes read thirst as hunger. Instead of "you need water," the feeling shows up as "you need food." I can half-explain it to myself. When you eat, you take in liquid too. A lot of fresh food carries water. So maybe, when my body wants water, it takes a shortcut and asks for the thing that happens to deliver both.
I can't prove that, and I'm not going to dress it up as a fact. But the practical danger is real either way: if the signal is ambiguous, you can put a meal's worth of calories into yourself when all the situation actually called for was a glass of water. That's worth knowing about once, so you can watch for it.
The habit that came out of this is the most useful thing in the whole piece, so here it is plainly. When hunger shows up at an odd time, I don't act on it immediately. I drink a large glass of water and wait about fifteen minutes. Then I check whether the hunger is still there.
Often it wasn't. And in those cases I'd have eaten for no reason, on a signal that resolved itself with water. When the hunger does survive the wait, fine, I eat, and now I'm fairly sure it was real. The cost of the check is fifteen minutes. The thing it saves, on the days it works, is a meal I didn't need.
There's a tool I used heavily during my big weight-loss stretch: zero drinks. Opinions on them are split, and I'll give you the other side fairly. Some people believe artificial sweeteners trigger a desire for sweets or carbs. That's plausible, and it might be true for you, so watch your own reaction honestly. It just wasn't my experience.
For me they did the opposite. They helped me manage hunger, including during fasting sessions that ran long. The specific approach mattered: I kept them cold and always available, and I took them in small amounts across the day. A little dose, then a gap, then another. That paced, unitized way of using them is what got me through a long stretch with no food coming in. I never wanted anything sweet; I just kept reaching for the cold drink. There's a common worry that the caffeine in some of them pulls liquid out of you, and occasionally too many gave me a mild headache, nothing serious. On balance they earned their place in my toolbox. Whether they earn a place in yours is yours to test.
Coffee is the one I'm least confident about. The common belief is that it dehydrates you, that the caffeine costs you liquid. In my case it never made me thirsty. It may have made me hungry, or done something else I can't name. I don't know the mechanism and I won't pretend I do.
What I'll flag is the stack, because that's where it got me. If you're already not drinking enough, and you might be leaning on food to supply some of your liquid, then adding a lot of coffee on top is a third thing pulling in the same direction. Over a couple of weeks or months, my experience was that this slowly added up into a state where I felt off and couldn't place why.
Under-hydration showed up strangely in me. For some people it's headaches. For me it was very often heavy tiredness and sleepiness after eating. Not every day. But now and then I'd eat a bit more than usual, some mix of Fat is a macronutrient that provides a concentrated source of energy at 9 calories per gram.Full definition → and Protein is one of the three macronutrients and plays a central role in appetite control and body composition.Full definition →, and it would knock me flat. I went hunting for exotic explanations. Food intolerance? An allergy? Some incompatibility?
Over time I found that when this started, drinking about four glasses of water usually fixed it. Not instantly, the body needs time to process it, but relatively quickly. Which pointed at a much more boring cause than the ones I'd been chasing. I'll repeat the caveat here because it matters most in this section: that was my pattern, you genuinely never know the full reality, and tiredness can come from many things. But if you're already experimenting and wondering what's going on, hydration is a cheap thing to rule out before you assume something is wrong with your food or your metabolism.
Three things, one common thread. Your signals may not be as clear as you assume. What reads as hunger was sometimes thirst, for me. Zero drinks were a genuinely useful tool through long fasts, caffeine worry and all. And coffee, which a lot of people use to push hunger down, may have been adding to the problem in my case rather than helping.
The shared lesson isn't a rule about water. It's a habit of pausing to investigate the feeling instead of obeying it on reflex. Drink a large glass of water. Wait fifteen minutes. Watch whether the hunger holds. Check your hydration before you decide something is wrong with your food, your metabolism, or your willpower.
This is exactly the kind of thing tracking is good for, and it's why I keep logging even when I'm not cutting. When you record what you ate and when, patterns like "I crashed after that meal" or "I ate three times in an afternoon that turned out to be a thirsty one" stop being vague memories and become things you can actually see. FastNow won't tell you to drink water and it won't diagnose anything; that's not its job and never will be. But it gives you the record that lets you notice your own patterns, which is the only way a habit like the fifteen-minute check ever gets built. Sometimes the answer really is simpler than you think. You just have to be paying enough attention to catch it.
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