How to Start Intermittent Fasting: The 16:8 Guide for Beginners

Intermittent fasting (IF) is an eating pattern that cycles between defined periods of fasting and eating. Unlike traditional diets, it doesn't prescribe what you eat — it focuses on when you eat. During the fasting window, your body exhausts its glycogen stores and begins drawing on fat for energy, which is the mechanism behind the weight-management benefits most people associate with the practice.

IF has been studied for a range of potential benefits beyond weight loss, including improved insulin sensitivity, reduced inflammation markers, and better blood sugar regulation. It is also associated with simplified meal planning — fewer meals means fewer decisions — which many people find reduces the mental load of eating throughout the day.

There are several IF protocols in common use: the 16:8 (sixteen hours fasting, eight hours eating), the 18:6, the 14:10 for beginners, and the 5:2 (normal eating five days per week, reduced calories on two non-consecutive days). Of these, the 16:8 is the most widely adopted because it slots naturally into everyday routines.

The 16:8 protocol means you fast for sixteen hours and eat within an eight-hour window each day. A common approach is to skip breakfast, eat your first meal at noon, and finish your last meal by 8 pm. Another popular window is 10 am to 6 pm for people who prefer an earlier dinner. The specific hours are less important than the consistency — your body adapts to a regular eating schedule quickly.

During the sixteen-hour fasting window, you can drink water, black coffee, and plain tea without breaking the fast. These drinks contain negligible calories and do not trigger an insulin response, so they preserve the metabolic state the fasting window is intended to create. Adding milk, sugar, cream, or flavoured syrups to coffee or tea will break the fast.

The eating window is not a licence to overeat. The 16:8 protocol works best when the meals you eat during the eight-hour window are nutritionally complete and appropriately sized. Many people find that two meals and a small snack fit naturally in an eight-hour window without calorie counting, and that the shortened eating period naturally reduces overall intake because there is simply less time to eat.

Starting with a 12-hour fast and gradually extending to 14 and then 16 hours over two to three weeks is an effective approach for complete beginners. The body adapts to using fat for fuel over time, and hunger hormones — particularly ghrelin, the hunger-signalling hormone — adjust to the new schedule within about a week. The first few days are typically the hardest.

The core principle is simple: anything that triggers an insulin response or provides meaningful calories breaks the fast. Solid food breaks a fast regardless of what it is. Drinks that contain calories — including fruit juice, smoothies, milk, bulletproof coffee (which contains butter and MCT oil), and any sweetened beverage — also break a fast.

Plain water, sparkling water, black coffee, and plain herbal or green tea are universally considered fast-safe. These contain either zero calories or trace amounts that do not produce a measurable insulin response. Some people extend this to include apple cider vinegar diluted in water, which is a common addition among experienced fasters.

The question of sweeteners is more nuanced. Some research suggests that certain artificial sweeteners — particularly those that taste sweet — may produce a small cephalic phase insulin response (triggered by taste alone, before the substance is absorbed). The evidence is mixed and the effect, where it exists, appears to be small. For strict fasting purposes, plain drinks without sweeteners of any kind are the safest choice.

Medications, supplements, and multivitamins vary in their effect on a fast depending on their calorie content and whether they should be taken with food. Water-soluble vitamins and most medications can be taken without breaking a fast, but fat-soluble vitamins (A, D, E, K) require dietary fat for absorption and are best taken during the eating window. Always check with a healthcare professional before combining fasting with any medication schedule.

Eat your last meal earlier than you usually would on your first day of fasting, so that your first fasting stretch ends at your planned meal time rather than requiring you to delay longer than expected. Setting a regular eating window and sticking to it on weekdays — even if weekends are more flexible — establishes the rhythm faster.

Stay well hydrated. Hunger and thirst feel similar in the body, and many people who struggle with the fasting window in the first few days find that drinking a large glass of water when hunger appears reduces the sensation significantly. Aim for at least two litres of water during the fasting period.

Keep the first few eating windows simple. Complex meals with a lot of variety tend to increase overall calorie intake. A protein-focused first meal — eggs, Greek yoghurt, fish, or chicken — combined with vegetables and a moderate amount of healthy fats keeps hunger suppressed for the rest of the eating window and reduces the urge to snack frequently.

Expect some adjustment discomfort. Headaches, mild fatigue, and difficulty concentrating are common in the first three to five days as the body adapts to longer fasting periods. These symptoms are usually short-lived and are often related to reduced caffeine intake, electrolyte shifts, or simply the body adapting to a new fuel source. They are not a signal that the protocol is not working.

The most consistent predictor of success with intermittent fasting is accurately tracking your fasting windows. It is easy to underestimate how much time has passed or to lose track of when the eating window closes, particularly in the early weeks when the schedule is not yet automatic. A dedicated fasting timer removes that uncertainty entirely.

Beyond timing, tracking your energy levels, sleep quality, and hunger patterns across the first few weeks gives you useful information about how your body is responding. Many people notice that energy is stable or improved within two weeks, and that hunger in the morning — which feels acute in the first few days — fades considerably as ghrelin adapts to the new schedule.

Weight changes in the first week are often due to water loss from reduced carbohydrate intake rather than fat loss. Measuring weight at the same time each day (morning, after using the bathroom, before eating) gives the most consistent data. Comparing weekly averages rather than daily readings removes the noise caused by normal fluctuations in water retention.

Use our fasting timer to track your 16:8 window accurately from day one. Set your fasting start time and let the timer count down your window — it takes the guesswork out of knowing exactly how far into your fast you are and when your eating window opens.