And while we're at it...what about other drinks? Would consuming things like lemon water or tea "ruin" your fastingand the benefits, weight loss-related and otherwise, that are supposed to come with it?
A little background: Intermittent fasting may help improve blood pressure, reduce liver fat, and lower cholesterol on top of reducing body weight, according to the University of Michigan Health Lab . Why tho? Well, the science is still somewhat undercooked, TBH. Theoretically, theres an exchange of sugar for energy that happens during intermittent fasting that could cause you to shed pounds.
When you deprive your body of calories, it goes into a temporary state of starvation and slowed metabolism that forces your fat cells to give up the glucose theyre storing in order to fuel your body, says registered dietitian Barbie Boules of Barbie Boules Longevity Nutrition . Over time, with repeated temporary fasting, this can lead to weight loss. (Fasting all the time would, in theory, permanently slow your metabolism and counteract the benefits, so you don't want to under-eat around the clock.)
But again, all of that's just a theory. We don't yet know conclusively what happens in humans [during fasting], and if it's any more beneficial than simply reducing overall calories, says Boules. What's more, so far the studies that have shown those positive results have mostly been in rats , not humans.
If youre still curious, though (I get it, it's trendy!), here's what you need to know about how an intermittent fasting diet will affect your drinking habits.
You're allowed to have coffee during the hours when you're fasting...but there's a catch.
Because a cup of brewed coffee is fat-free and almost no-cal, it wont screw up your fast...so long as it's black coffee, says Boules. All your regular coffee variations and add-ins will cost you fat and caloriesand consuming fat and calories means you are no longer fasting.
According to the USDA, plain black coffee is around two to five calories (per cup). But once you start pouring in sugar, milk, or cream, youre adding anywhere from 16 to nearly 100 more calories to your morning joe. So while coffee can be a decent way to feel like youre consuming something during your fasting hours, make sure youre drinking it black to keep your calories almost nonexistent. The more calories you feed your body, the more outside fuel it has to use as energy, which means it won't utilize the glucose stored up in your fat cells, in theory. Fast, broken.
But you dont necessarily want to start a coffee-drinking habit just to soothe your hunger pains if you're doing intermittent fasting. Caffeine can temporarily speed metabolism and potentially take you out of that starvation mode. "But if you're [already] a regular caffeine consumer, the thermogenic effect is minimal, explains Boules.
In other words, if youre already addicted to an a.m. coffee, you should be okay: The calories are minimal and your body is adjusted to the caffeine. But if you were a decaf tea drinker before, dont start chugging espresso, mmkay?
Ummm, I hate coffee...what else can I drink while I'm in a fasted state?
Obviously, you can drink wateryou can even punch it up with some fresh fruit or a squeeze of lemon for flavor as long as you arent actually eating the fruitbut Boules says you can also reach for unsweetened tea, which is zero calories without anything extra added to it.
What you cant drink, however, are things like fruit juices, green juices , or smoothies . This trips people up sometimes, because we tend to think stuff in liquid form is calorie-free, just like water. But juices and smoothies are made with food, which means they have enough calories to break your fast.
The whole idea behind the alleged health-promoting benefits is actually fasting (i.e., zero calories or energy intake), says Boules. [If youre] consuming something caloric during fasting hours in the form of sweetened beverages, juices, or even smoothies...you're not fasting.
Remember, the whole concept of intermittent fasting relies on a prolonged, uninterrupted period of not consuming any calories (otherwise, your body wont go into the state of starvation necessary for your insulin levels to drop and your body to burn fat).
Most people opt for a 16:8 dietfasting for 16 hours per day and eating during an 8-hour windowthough it's not totally clear as of now if 16 hours of intermittent fasting is the magic number of fasting hours to see weight-loss results. But, that's a reasonable rule to follow until science reveals more about IF. (A 2016 study actually proposed an 18-hour fast for maximum weight lossbut the sample size was tiny, only 11 people.)
What if I want something other than a drink while I'm intermittent fasting?
Unfortunately, Boules says that consuming any calories your body could convert to energy for fuel means you are not fasting anymore. Period.
So what can you chew on? Well, its not terribly exciting, but feel free to reach for some sugar-free gum or hard candy with sugar alcohols or non-nutritive sweeteners like xylitol, which Boules says dont affect your calorie intake or blood glucose in the way that regular sugar does, so you won't be breaking your fast. (But the artificial kinds could cause some bloating or mild GI upset, FYI).
Theres always good old-fashioned, zero-calorie ice cubes if you need to distract your mouth while answering emails at your desk.
The bottom line?
Water, coffee, and unsweetened tea is okay during fasting hours, and sugar-free gum, sugar-free hard candy, or ice cubes may satisfy your oral fixation until the late afternoon. But if youre finding that youre a raging hunger monster while doing intermittent fasting or just otherwise totally miserable, its okay to quit and try something elsefasting certainly is not for everyone .
If you are genuinely physically and emotionally nourished and satisfied [while] confining food to a set number of hours per day, do you, says Boules. If you're not, just understand this is not required to achieve your goal of good health.