Before diving into what you can and can’t eat during a fast, it’s important to get clear on why you’re fasting in the first place. It only makes sense that different food items can support different goals!

So, Why Do You Fast?

Generally, there are three main reasons to observe a fast. The most common reason, especially as far as intermittent fasting is concerned, is weight loss. If this is your goal, you’re after two things: calorie restriction (duh), and improved sensitivity to the blood-glucose-lowering hormone insulin. Having an empty stomach for at least 16 hours a day will definitely help.

Another reason for periodic fasting is longevity and overall health. If this is what you’re after, then your goal is autophagy, a process of cleaning out damaged cells, in order to regenerate newer, healthier cells. The general consensus is that autophagy kicks in full force about 24 hours into your fast.

The last reason for fasting is gut health, which has gained more and more popularity. We know surprisingly little about how our gut microbiome works and what exactly it needs to stay diverse and healthy, but we know for sure that fasting can favorably influence the gut flora. If that’s your reason for fasting, then you’ll need the most discipline. Literally everything except water will break your fast’s ability to support gut health, period. Your gut can’t rest when it’s busy processing your stomach’s contents.

Those of us who fast for weight management or longevity are luckier, though. The general rule of thumb is this: If it’s calorie-free or has fewer than 50 Calories, it will not break your fast. Things get a little more complicated if you’re fasting for health as opposed to weight loss, though, and this is mostly due to the limited research.

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That’s All Good and Well, But Tell Me Already — What Can I Have?

Again, it depends on your goals. To help you get the most out of your fasts, here’s a list of food items that will and won’t support your particular fasting goals.

Black coffee: Does not break a fast

Coffee with milk: Does not break a fast if you keep it under 50 Calories (±50 ml or 1.7 oz of milk)

Coffee with cream: Does not break a weight-loss fast if you keep it under 50 Calories (±2 teaspoons of cream); may break a longevity fast, regardless of the amount of cream

Bulletproof coffee: Likely does not break a weight-loss fast, but may break a longevity fast

Tea: Does not break a fast if no sweeteners are used (see below for more details on sweeteners)

Bone broth: Breaks a fast

Apple Cider Vinegar: Does not break a fast

Regular chewing gum: Breaks a fast

Sugar-free gum: Does not break a fast (depending on the sweetener used)

Diet soda: May break a fast if sweetened with sucralose

Aspartame-sweetened sodas: Likely break a longevity fast and a weight-loss fast

Stevia: Does not break a fast

Monk Fruit: Does not break a fast

Sugar Alcohols (sorbitol, mannitol, xylitol, maltitol, maltitol syrup, lactitol, erythritol, isomalt and hydrogenated starch): Likely do not break a fast

Hopefully, this list will help you the next time you’re in your kitchen mulling over whether something will break your fast. But remember, you’ll get the most benefit out of your fast if you fully commit and stick to water.

That said, adding some ice, a squeeze of lemon juice, and a dash of stevia will make that glass of water a much better alternative to a diet coke. So feel free to cut the corners a little when needed. After all, what good is a healthy eating habit if you have to suffer and struggle to sustain it in the long run?

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