Can You Drink Coffee While Fasting?

Different types of fasting, including intermittent fasting and longer fasts, have become increasingly popular in recent years. The reported benefits include weight loss, improved metabolic health, and, some advocates say, possibly improved mental clarity.

However, there’s a question as to whether it's okay to drink coffee whilst not eating that hangs over the heads of fasting enthusiasts who also love their daily coffee fix. In this article, we’ll delve deeper into the topic and explore what you need to know about coffee intake during your fasting periods.

What is fasting?

Fasting refers to voluntarily abstaining from certain food and drinks for a set period of time. Normally, during a fast, no solid food is consumed, and only low or no-calorie drinks are permitted. However, certain religions suggest complete abstinence from any type of liquid during fasts.

A fast could be short, lasting only a few hours, or even stretch to longer periods of time. One of the most popular fasting methods is called intermittent fasting, which involves dividing your day or week into ‘eating windows’ and ‘fasting windows.’

During an intermittent fasting window, you don’t consume anything that contains calories that could break the fast. In order to fast correctly, it’s important to know what you can and can’t consume to ensure you don’t disrupt the process.

Can you drink coffee while fasting?

There isn’t a straightforward yes or no answer to this question because it all depends on the way you drink your coffee. A straight-up black coffee contains zero calories and is generally acceptable to consume while intermittent fasting. However, many of us like to add calorie-containing ingredients like cream, sugars, and different types of milk, which, while delicious, can actually break your fast.

During fasting and intermittent fasting periods, it's important to keep your coffee as low or no-calorie as possible.

Black coffee is the most popular choice among those who practice intermittent fasting because it contains virtually no calories and may potentially offer benefits like appetite suppression and mental alertness.

Benefits of drinking coffee while fasting

As long as you don’t add calorie-containing additives such as cream, cow's milk, butter, coconut oil, or sweetened nut kinds of milk to your brew, drinking black coffee during your intermittent fasting periods may potentially hold some health benefits.

Appetite suppression

There is a perception that coffee has the ability to suppress your appetite, potentially leading to less calorie consumption and helping you to lose weight. It’s generally through anecdotal evidence that we see this trend, and there’s limited scientific exploration into the actual mechanisms through which coffee might promote weight loss.

This study investigated the effects of different amounts of caffeine on dietary intake and appetite of 16 normal-weight and 17 overweight/obese participants taking part in three trials. During the trials, they consumed a regular breakfast along with either 200 ml of coffee with 3–6 mg caffeine per kg of body weight or water. The participants recorded their appetite feelings at various time points during the three hours following breakfast and drink consumption. At the 3-hour mark, participants ate a meal with no restrictions on the amount of food consumed and reported their food intake during the experimental day.

The researchers suggested that after coffee, containing 6 mg of caffeine per kilogram of body weight, intake, the overweight participants tended to consume less in the following meal and throughout the day. However, no change was recorded for those classed as being normal weight.

Another 2017 comprehensive review examined the evidence surrounding coffee and caffeine's influence on appetite and energy intake, gastric emptying, appetite-related hormones, and perceived measures of appetite.

The review indicated that coffee intake at 3–4.5 hours before eating a meal had minimal influence on food intake, whereas caffeine ingested 0.5–4 hours before a meal may be an appetite suppressant. The researchers noted that the literature didn't offer any conclusive evidence to firmly establish an influential link between coffee and caffeine on gastric emptying, appetite hormones, and appetite perceptions. They concluded that longer controlled studies are needed, which take into account other factors, such as the genetics of caffeine metabolism.

Mental clarity and alertness

It’s commonly believed that coffee is a stimulant. You might have heard coffee advocates say that it boosts mental capacity, gives an extra energy kick to get a project finished, or even simply helps to get up and out of the house in the morning.

It’s understandable that while intermittent fasting, we still want to stay as alert and aware as normal, and plain black coffee might be able to help. A recent 2020 study examined the results from a 2011–2014 National Health and Nutrition Examination Survey. It explored the self-reported effects of caffeinated and non-caffeinated coffee on the cognitive performance of 2,513 adults aged 60 or older.

Researchers noted an improvement in cognitive function for the caffeinated group, which wasn’t present in the group who drank decaf coffee. While this appears promising, it's vital to acknowledge that these effects were self-reported. In order to establish more firm conclusions, longer controlled studies are needed.

This 2018 randomized, placebo-controlled, double-blind, counterbalanced-crossover study published in Nutrients looked into the acute effects of caffeinated black coffee on cognition and mood in 29 healthy young and 30 older adults.

The study suggested that both regular and decaf coffee improved alertness compared to the placebo. Regular coffee was also shown to have higher digit vigilance accuracy compared to both decaf and the placebo. Interestingly, it was observed that regular coffee decreased reaction time in comparison to the placebo.

Metabolic benefits

There has been interest in the relationship between caffeine and coffee and metabolic health for decades. This study, published in 1989, explored the influence of caffeine on thermogenesis and energy expenditure in lean and post-obese human volunteers. It was suggested that even with as little as a single oral dose of 100 mg of caffeine, it may increase basal metabolic rate, fat oxidation, and energy expenditure.

However, in relation to intermittent fasting, until this day, there’s very little scientific literature that offers insights into the effects of coffee on the metabolic health of someone in a fasted state. It’s impossible to say with any certainty that drinking coffee during your fast will or won’t improve your metabolic well-being.

The risks of drinking coffee while fasting

If you are considering a fast and want to keep drinking coffee, there are some potential health risks that are worth thinking about before you brew a cup.

Digestive issues

Digestive discomfort is something you may experience when drinking coffee on an empty stomach. This could be cramps, acid reflux, heartburn, or other gastrointestinal unease.

Possible blood pressure elevation

Coffee is known to raise blood pressure, which could have implications for individuals with conditions such as hypertension. If you know you have issues with blood pressure, it’s recommended to speak with your primary healthcare team about fasting, coffee, and caffeine consumption.

Excessive coffee consumption

Drinking too much coffee can cause some health hazards, especially for individuals with existing heart conditions. Sensations such as jitters, feelings of anxiety, sleep disturbances, or temperature fluctuations should not be ignored. Although with moderate coffee consumption, these symptoms are usually transient, mild, and reversible, the data for caffeine intakes greater than 600 mg is limited.

It's recommended to exercise caution with the amount of coffee you drink — stick within the recommended guidelines and do not exceed 400 mg of caffeine per day. If you have any heart-related conditions, it would be best to get advice from your healthcare team before fasting and drinking coffee.

What can you put in coffee that won’t break a fast?

As a general rule, your coffee should be black and without any extras in order to maintain your fast. But, if you are used to putting other ingredients like cream, milk, or sugar in your coffee, it may be a shocking experience to you (and your tastebuds) to go headfirst into a long black. Here are a few suggestions you can add that might enhance the flavor experience but won’t have a significant impact on your fast.

• Cinnamon. Adds a sweet and warming flavor without any calories.
• Vanilla extract. As long as it’s unsweetened, one or two drops of pure vanilla may enhance the taste of your coffee without breaking your fast, as it contains low or no calories in small doses.
• Unsweetened alternative milk. If you really can’t manage without some kind of milk, then you can use a small amount of unsweetened almond, oat, or soy milk as it contains few calories and won’t disrupt an intermittent fast.

Alternatives to coffee that are suitable for fasting

There are plenty of alternatives to coffee that you can drink during a fasting window. The following options will give you flavor and hydration without disrupting your fast.

• Herbal teas. There are so many different herbal teas to try, and most of them are totally calorie-free. Check the box for the nutritional information to make sure there aren’t any hidden additives or sweeteners that affect the calorie count.
• Green tea. Well-known in the health world for its antioxidant properties, green tea is a delicious and refreshing alternative to a cup of coffee. And it contains caffeine, so you might still get an energetic buzz.
• Water. It might sound obvious, but drinking water during a fast is a great way to stay hydrated while your digestive system takes a break.

Final thoughts

You can still enjoy coffee while intermittent fasting as long as you stay mindful about what you add to it. Straight-up black coffee is one of the best ways you can ensure you still get your caffeine kick but without any fast-disrupting calories. Adding cinnamon or pure vanilla extract is a great option for coffee drinkers who need a little extra flavor.

One thing to be conscious about is the amount of coffee you drink. According to the FDA, 400 mg is considered a safe daily amount, but you might want to try drinking less coffee than you usually do while you are fasting to see how it affects you when your stomach is empty.

Intermittent fasting isn’t something to just try on a whim. Skipping breakfast and filling your grumbling stomach with a cup of coffee isn’t a magic wand for losing weight, improving your metabolism, or sharpening your mind. And, although we’ve all seen fitness influencers touting the benefits of drinking coffee during a fasting window, it’s best to consult with a registered dietician or physician before voluntarily giving up food. They can help you design a balanced diet and exercise plan that will get you to your health goals safely and sustainably.