For a lot of people, the day doesn’t begin with sunlight or a stretch—it begins with a cup. The first sip of coffee feels like flipping a switch: the fog lifts, the brain sharpens, the body wakes up. It’s a ritual so common that we rarely question it. But there’s a growing body of research and clinical discussion around a simple twist that can change how coffee feels in your body: whether you drink it before you eat.
The claim you shared—coffee on an empty stomach can amplify stress by driving a sharper cortisol response—sits at the intersection of two real physiological facts: cortisol is naturally high in the morning, and caffeine can stimulate cortisol release in many people. Add in an empty stomach and fragile blood sugar after sleep, and for some bodies the result is a “wired-but-wobbly” start: jitters, anxiety, stomach discomfort, or a crash that lands hard a couple hours later.
It doesn’t mean coffee is “bad.” It means timing—and context—can matter more than we assume.
The cortisol story: why mornings are different
Cortisol gets painted as the villain because it’s called “the stress hormone,” but it’s more accurate to say it’s one of the body’s main energy and alertness regulators. It helps raise blood sugar, mobilize energy, and prepare you to meet the day. Cortisol typically rises around waking as part of your circadian rhythm—your internal clock—and this morning surge is one reason you can open your eyes and function at all.
Now bring caffeine into that system. Caffeine doesn’t create energy from nowhere; it blocks adenosine (the “sleep pressure” signal), and it can also activate stress-response pathways in ways that vary by dose and by individual sensitivity. Controlled research has shown caffeine can increase cortisol secretion, and regular use may reduce but not fully eliminate that response.
So the question becomes less “Does coffee raise cortisol?” and more: When does it do so most noticeably, and in whom?
For many people, the answer is: when cortisol is already peaking (morning) and the body has no nutritional buffer (empty stomach).
The University of Bath angle: stress isn’t just cortisol
You mentioned the University of Bath research, and it’s important to be precise about what that study emphasized.
Bath researchers published findings showing that strong black coffee consumed before breakfast can substantially increase the blood glucose response to breakfast—by around 50%—especially after a night of fragmented sleep. In simple terms: coffee-first can make your body handle the first meal’s sugar worse—your system reacts as if the meal hit harder.
That matters because metabolic stress and hormonal stress are not separate worlds. Blood sugar spikes and crashes can mimic or amplify anxiety symptoms: shaky hands, fast heart rate, irritability, brain fog, and that edgy “something’s off” feeling. Even if cortisol is the headline, unstable glucose can be the hidden co-star.
So if someone says, “Coffee on an empty stomach makes me anxious,” what they may be experiencing is a combined effect: a caffeine-driven alertness surge layered on top of a system that hasn’t been stabilized by food yet.
Why some people feel fine and others feel awful
This is where coffee becomes personal.
Two people can drink the same espresso at 7:00 AM and have totally different outcomes. One feels focused and calm. Another feels jittery and restless. A few reasons explain why:
Caffeine sensitivity and genetics. Some people metabolize caffeine quickly; others break it down slowly, meaning the same cup hangs around longer and hits harder.
Habit and tolerance. Daily caffeine use can blunt some hormone responses, but research suggests it may not eliminate cortisol effects completely—especially under certain conditions like stress, poor sleep, or higher doses.
Sleep quality. After a poor night, your body is already under strain. Bath’s work suggests the coffee-before-breakfast scenario can be particularly disruptive after fragmented sleep.
Baseline anxiety. If your nervous system already runs “hot,” caffeine can push it from functional alertness into fight-or-flight.
What kind of coffee and how much. A milky latte behaves differently than a strong black coffee. A single cup differs from a giant mug you sip quickly.
Stomach and gut sensitivity. Coffee can increase gastric acid and speed gut motility, which for some people means nausea, reflux, or urgent bathroom trips—sensations that can themselves feel like anxiety.
So yes—some people can drink coffee on an empty stomach for years and feel perfectly fine. But for many others, it’s one of the simplest fixable triggers of morning stress.
The “empty stomach” effect: why food changes the experience
Eating before coffee does not “cancel” caffeine. It changes the way your body receives it.
Food can slow absorption a bit, soften the spike, and provide a metabolic foundation—protein, fats, and fiber especially help stabilize blood sugar. The result is often a smoother, steadier energy curve instead of a sharp rise and a sharp fall.
Think of it like pouring coffee into your body’s system when it has no scaffolding yet. Caffeine is a loud signal. If the system is steady, it’s productive. If it’s fragile, it feels like chaos.
This is why many people report the exact same coffee feels completely different depending on whether they ate.
What the “jitter-crash” cycle really is
People often describe this morning pattern:
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Coffee hits fast → alertness, motivation, even euphoria
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Then comes the edge → racing thoughts, shaky body, tension
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Then the dip → hunger, fatigue, irritability, brain fog
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And the solution becomes… more coffee
This is not always addiction. Sometimes it’s a feedback loop created by timing—caffeine layered onto an empty tank, with glucose instability amplifying the rollercoaster.
Bath’s findings on impaired glucose response after coffee-before-breakfast help explain why some people feel like their energy is “broken” despite doing the normal morning routine.
The myth: “Coffee causes stress”
Coffee doesn’t automatically “cause stress.” It can, however, activate the physiology of stress, especially when combined with other stressors.
Caffeine can elevate cortisol, and research has explored how caffeine interacts with stress and daily hormonal patterns. But the human experience of stress isn’t just cortisol readings. It’s the feeling in your chest. The tension behind your eyes. The restless legs. The inability to relax into the morning.
If coffee-first gives you that sensation, your body is giving feedback—not moral judgment.
So should everyone stop drinking coffee first thing?
No. But many people should reconsider how they do it.
If you drink coffee first thing and you feel good—steady energy, calm focus, no stomach problems—you likely don’t need to panic.
But if you relate to any of these, experimenting with timing is worth it:
You feel anxious or shaky after morning coffee.
You get acid reflux, nausea, or a gnawing stomach feeling.
You crash mid-morning and need more caffeine to survive.
You feel “wired” but not actually productive.
You had poor sleep and coffee hits like a punch.
In those cases, the solution is often not quitting coffee. It’s changing the order of operations.
A practical, real-life approach that doesn’t ruin your morning
Most people won’t suddenly become breakfast lovers. So here’s a practical approach that keeps it realistic:
Start your morning with water. Your body is mildly dehydrated after sleep, and dehydration can amplify cortisol-like symptoms.
Eat something small. Not a full meal if you’re not hungry—just a buffer. A boiled egg, yogurt, a banana with peanut butter, a handful of nuts, even a slice of toast. The goal is not perfection. The goal is a foundation.
Then drink coffee. Many people find the same coffee becomes smoother, less edgy, and more stable.
If you love your ritual, keep the ritual—just add a small anchor before it.
The bigger perspective: your morning sets your nervous system tone
Here’s the deeper point behind this whole conversation: morning habits don’t just affect energy—they shape your nervous system’s “default setting” for the day.
If your day begins with a sharp physiological spike, your brain can interpret that as urgency. You may feel rushed, tense, reactive, even if nothing bad is happening. If your day begins with steadier signals—hydration, nutrition, calmer caffeine timing—your baseline often becomes more grounded.
It’s not magic. It’s physiology.
And that’s why the “coffee after breakfast” idea has become so sticky: it’s a small change with outsized payoff for the people who need it.
The most honest conclusion
The research doesn’t say coffee is dangerous. It says timing matters, especially in the morning when hormones and metabolism are already shifting. Bath’s work adds a strong, concrete piece of evidence that coffee-before-breakfast can impair metabolic response, which may feed into the stress-like feelings many people report. And broader research supports that caffeine can affect cortisol secretion, with individual tolerance playing a big role.
So if coffee on an empty stomach makes you feel like your body is in “fight mode,” that’s not you being dramatic.
That’s your biology asking for a better order.
If you want, I can turn this into a tighter viral-style article version too (same facts, more punchy storytelling, still magazine flow).