Intermittent fasting (IF) has become not just a global health and fitness trend, but a way of life.
According to Healthline: 
Intermittent fasting is an eating pattern where you cycle between periods of eating and fasting.
It does not say anything about which foods to eat, but rather when you should eat them.
Doing IF is not just for losing weight, but also for better metabolism, improving medical conditions like diabetes, more optimal brain activity, a stronger immune system, and basically living longer[2, 3, 4].
While it focuses more on when to eat, rather than what, many people still ask this big question:
Can you drink coffee or tea while intermittent fasting?
According to Dr. Akil Palanisamy, physician and author of The Paleovedic Diet:
"Autophagy is the self-cleaning process by which the body's cells break down and recycle damaged proteins and components. This is activated by intermittent fasting, but anything other than water (even black coffee) disrupts it to some extent.” 
Dr. Rhonda Patrick, a Ph.D in biomedical science and expert on nutritional health, seems to agree in this interview with Joe Rogan. She says that drinking black coffee, green tea and vitamin supplements break the fast.
On the other hand, some experts agree in saying that caffeine is okay while fasting, but only to a certain extent:
“Zero-calorie beverages are okay. As previously stated, I drink green tea in the morning for my caffeine kick while writing. If you want to drink water, black coffee, or tea during your fasting period, that’s okay. Remember, don’t overthink it – keep things simple! Track your results, listen to your body.”
"If you’re on a time-restricted fast and you’re in no-eating hours, it’s best to stick to no- or low-calorie drinks like water, coffee (with no milk) and tea. If you’re on an alternate day diet or something similar, even during low calorie hours, you can technically drink whatever you’d like — but remember, this will count against your calories. Would you rather spend 100 calories on an apple or a glass of milk? It’s your call.” 
Is having black coffee fasting? Doctors keep telling patients it is all right to have black coffee before fasting blood work (fasting sugar, fasting lipid panel).
It depends to some extent on what test is being performed, but for many tests that require fasting, intake of non-carbohydrate containing liquids a few hours before testing will not impact results. We have worked here to make 1 standard definition of “fasting” that encompasses most test requirements. We allow clear liquids (water, black coffee) up until 2 hours before a test or procedure. The definition of fasting should be clarified for all procedures in your institution if possible.
Good news - the answer is a resounding YES!!! Here are four (4) reasons why you should NOT ditch your coffee just yet:
Caffeine boosts your metabolism.
If weight loss is your primary goal for doing intermittent fasting, then this is music to the ears. There are 3 ways that caffeine boosts your metabolism:
It suppresses appetite.
According to Livestrong, caffeine can help you lose your appetite: 
In a study published in "Clinical Nutrition" in January 2009, 27 participants consumed capsaicin, which occurs naturally in hot peppers; green tea, which contains caffeine; sweet peppers; capsaicin plus green tea; or a placebo on 10 separate days. Researchers then analyzed the participants' appetite, food intake, body weight and heart rate and found that green tea consumed with or without capsaicin led to increased satiation, or fullness, and reduced calorie intake.
It keeps you in a happy disposition.
We talked about this at length in the article How does caffeine affect your mood.
It keeps you alert and attentive, eases and reduces the risk of depression, helps you get along with people better, and basically just turn you into a walking ball of sunshine.
These are the things you especially need when going through intermittent fasting!
It’s a way to treat yourself.
When doing something that’s beyond your usual rhythm, you need something to motivate you and keep you happy.
If you’re a coffee-lover, having your usual cup of joe is definitely one way to treat yourself and one piece of normalcy you can have during the “ordeal” of fasting - which isn't easy!
And just by taking some of the experts’ advice above, you’ve got nothing to lose by having your java fix!
Read our article What coffee and caffeine do to you when fasting to find out more.
Coffee, tea and other forms of caffeine are allowed in intermittent fasting, except for when they contain sugar and exceed a certain amount of calories.
Our take? Keep it to a low-calorie count and you can enjoy the benefits of caffeine and intermittent fasting altogether!
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Some research has suggested that caffeine may stimulate thermogenesis - a scientific name for the way your body generates heat and energy from the calories in your food; but nutrition experts say that this effect probably isn't enough to produce significant weight-loss. Caffeine may also reduce your desire to eat for a brief time, but again, there's no good evidence over the long-term that this effect leads to weight-loss. To date, no conclusive clinical studies have been done to determine the long-term effect of caffeine on weight loss, and the smaller studies that have been done show a lot of variability in the outcomes.
Want to hear something shocking?
Having your caffeine fix first thing in the morning will NOT perk you up.
But the good news is, you no longer need to make that sluggish early morning trip to the coffee-maker daily, nor join that long rush hour queue in your go-to café.
If you’re wondering whether we’re pulling some sick April Fool’s joke in the middle of August, there’s actually scientific evidence to all of this.
If you’re trying to lose weight (or at least not gain a few extra pounds), then the best thing to do is eat healthy and go to the gym more religiously, right?
But if you’ve been going at it for a while now and haven’t been seeing much progress, then you may want to look into something else.
Like your coffee consumption.
Now you may ask: what does an innocent cup of joe have to do with weight gain?
Let me tell you.
It’s not as innocent as it seem.
That cup of coffee you buy on your way to work? It may be sneaking in a few extra calories (more than you’d like and expect). And if you buy more than one cup a day, you may be racking up a few calories from a “dessert” that disguises itself as your go-to caffeine fix.