Can I Drink Milk During 16 Hours Fasting?

October 18, 2025 •

4 min read

Over 7 million searches for intermittent fasting are conducted every month, revealing the widespread interest in this eating pattern. The simple answer to a common question is that consuming milk during a 16-hour fasting window is not recommended, as it contains calories and sugar that will break your fast.

Quick Summary

Milk contains calories and natural sugars that stimulate an insulin response, ending a fasted state. For a strict 16-hour fast focused on metabolic benefits like autophagy and fat-burning, it is best to avoid all dairy and other caloric drinks. The impact varies depending on the amount and individual metabolism.

Key Points

Milk breaks a fast: Any type of milk, dairy or plant-based, contains calories, protein, and sugar (lactose) that will end your fasted state.
Insulin spike is the issue: The natural sugars and protein in milk trigger an insulin response, shifting your body from fat-burning to glucose metabolism.
Autophagy is inhibited: Consuming milk, even in small quantities, can disrupt the cellular repair process known as autophagy, a key benefit of fasting.
Strict vs. 'dirty' fasting: For strict fasting benefits, aim for zero calories. A small splash might be acceptable for 'dirty fasting' but is not ideal and may inhibit certain benefits.
Stick to zero-calorie drinks: Safe drinks during a 16-hour fast include plain water, black coffee, and unsweetened tea.
Time your milk intake: Save milk and other caloric beverages for your designated eating window to avoid breaking your fast.

The Core Principle: Why Milk Breaks a Fast

During a 16-hour intermittent fast, the body enters a metabolic state where it burns stored fat for energy, a process known as ketosis. A primary goal is to keep insulin levels low, as this hormone is triggered by calorie and sugar intake. When insulin levels are elevated, the body shifts from burning fat to using glucose from the consumed calories for fuel, which effectively ends the fast and its benefits.

Milk's Nutritional Breakdown

Calories: All forms of milk—including whole, skim, and plant-based alternatives—contain calories. A single cup of whole milk has around 149 calories, a cup of rice milk has about 120 calories, and even unsweetened almond milk can have 30-60 calories. Any caloric intake technically breaks a fast, especially if the goal is to maximize metabolic rest or autophagy.
Lactose (Sugar): Milk contains lactose, a natural sugar. When consumed, the body breaks lactose down into glucose, which triggers an insulin response. This insulin spike is what pulls your body out of the fasted state, halting the cellular repair processes and fat-burning benefits.
Protein: The protein in milk can also stimulate insulin release, particularly in larger amounts.

The Difference Between Strict and 'Dirty' Fasting

For those who are more lenient with their fasting, a concept known as 'dirty fasting' allows for a minimal calorie intake, often cited as under 50 calories. In this scenario, a small splash of unsweetened almond milk in coffee might not completely derail the metabolic benefits for weight loss, though it will still technically end a 'clean' fast. However, even this small amount can inhibit deeper fasting benefits, such as autophagy.

What About Plant-Based Milks?

Just like dairy milk, plant-based alternatives contain macronutrients and calories that break a fast. Unsweetened almond milk, for instance, has fewer calories than cow's milk but is not calorie-free. Flavored or sweetened plant milks contain significantly more sugar and calories, making them an immediate fast-breaker. The safest bet for a clean fast is to avoid all milks and creamers.

The Impact on Autophagy

Autophagy is the body's natural process of recycling and cleaning out old, damaged cells, and it is a key benefit of longer fasts, including the 16:8 method. Stimulating insulin through the consumption of calories, even in small amounts, can inhibit this cellular process. Therefore, if maximizing autophagy is your primary goal, a strict zero-calorie rule is essential, meaning no milk or other caloric beverages.

Comparison of Fasting-Friendly Beverages vs. Milk


Beverage	Fasting-Friendly?	Calories	Insulin Impact	Notes
Black Coffee	Yes	~2-5 kcal	Minimal	Can be consumed plain; avoids additives.
Unsweetened Tea	Yes	~0-2 kcal	None	Herbal or black teas are fine without added milk or sugar.
Plain Water	Yes	0 kcal	None	Essential for hydration during any fast.
Bone Broth	Technically breaks fast	~15-45 kcal	Moderate	Can be used for modified fasts, but contains protein and calories.
Dairy Milk	No	100+ kcal	Significant	Contains sugar (lactose), protein, and calories.
Plant-Based Milk	No	30+ kcal	Varies	All plant milks contain calories; unsweetened is lower but still breaks a clean fast.

Practical Fasting Tips to Avoid Milk

If you are accustomed to having milk in your morning coffee or tea, transitioning to a zero-calorie drink can be a challenge. Start by trying your favorite hot beverages black. If you prefer a smoother taste, explore unsweetened herbal teas. Many find that quality coffee beans and different brewing methods, like a cold brew, can change the flavor profile enough to make black coffee more palatable. For hunger suppression, some find success with drinks like diluted apple cider vinegar, though this also depends on personal metabolic response.

Conclusion: The Definitive Answer

For a true, clean 16-hour intermittent fast designed to maximize benefits like fat-burning and cellular repair (autophagy), the answer is a definitive no, you cannot drink milk. Milk contains calories and natural sugars that trigger an insulin response, which pulls the body out of its fasted state. While a minimal amount might not significantly hinder weight loss goals for some people following a 'dirty fasting' approach, it still compromises the stricter metabolic and cellular benefits. Stick to zero-calorie beverages like plain water, black coffee, or unsweetened tea to ensure your fast is successful.

Navigating Fasting and Dairy Consumption

The best practice is to consume all dairy products, including milk and plant-based substitutes, exclusively during your eating window. By reserving milk for your feeding period, you can still enjoy its nutritional benefits without compromising your fasting efforts. Planning your meals and drinks in advance can help prevent accidental fast-breaking and maintain consistency with your routine. For those who struggle with hunger during the fasting window, there are many effective, zero-calorie alternatives available. For more detailed information on intermittent fasting, resources from organizations like the National Institutes of Health are available.

Frequently Asked Questions

Yes, a splash of milk will technically break your fast because it contains calories, sugar (lactose), and protein. While some argue a tiny amount has a negligible effect, for a true fast and to maximize benefits like autophagy, it should be avoided.

No, unsweetened almond milk contains calories and macronutrients, even if it's a small amount. Any calorie intake triggers a metabolic response that ends a clean fast.

Technically, any amount of calories breaks a fast. The common, unofficial guideline of staying under 50 calories is more for a 'dirty fast' and will still inhibit deeper fasting benefits like autophagy.

Acceptable drinks are those with zero or near-zero calories, including plain water, black coffee, and unsweetened herbal or black tea.

Yes, bulletproof coffee (coffee with butter and/or MCT oil) contains a significant number of calories from fat, which breaks a traditional fast. While it won't spike insulin like sugar, it still provides fuel and ends the fasted state.

Yes, milk is perfectly fine to consume during your eating window. Simply ensure it aligns with your overall nutritional goals, as it contains calories and sugar.

If you accidentally consume milk, the best approach is to simply continue your fast until the next planned eating window. Don't be discouraged; consistency is more important than perfection.