How Long Does It Take for 16/8 Intermittent Fasting to Work

How Long Does It Take for 16/8 Intermittent Fasting to Work

How Long Does It Take for 16/8 Intermittent Fasting to Work for Weight Loss?


Intermittent fasting has gained significant popularity as an effective approach for weight loss and improved metabolic health. Indeed, one popular method within the realm of intermittent fasting is the 16/8 method, which involves fasting for 16 hours and restricting eating to an 8-hour window. If you're considering adopting the 16/8 intermittent fasting approach for weight loss, you may wonder how long it takes to see results. Hence, we will explore the effectiveness of the 16/8 method for weight loss, the factors that influence results.  Finally, we will also look at how long it takes for 16/8 intermittent fasting to work.

What is Intermittent Fasting?

Intermittent fasting (IF) is an eating pattern that cycles between periods of eating and fasting.  It alternates between designated eating windows and fasting periods. Rather than focusing on what foods to eat, intermittent fasting primarily emphasizes when to eat. There are various approaches to intermittent fasting.  However, the most common methods involve dividing the day or week into eating and fasting periods. For instance, the 16/8 intermittent fasting method works by fasting for 16 hours each day and restricting eating to an 8-hour window, while the 5:2 approach involves consuming a regular diet for five days a week and drastically reducing calorie intake (to about 500-600 calories) for the remaining two non-consecutive days.

The idea behind intermittent fasting is to induce metabolic changes in the body that can lead to numerous potential health benefits. During fasting periods, the body's insulin levels drop.  This causes the body to use stored fat as an energy source. This process, called ketosis, can facilitate weight loss by burning fat. Additionally, intermittent fasting may promote cellular repair processes, improve hormone levels related to metabolism, increase human growth hormone production, and support brain health. While intermittent fasting has gained popularity for its potential health advantages, it's essential to approach this eating pattern sensibly and consider individual health conditions, lifestyle, and nutritional needs before adopting any fasting regimen. Consulting a healthcare professional or nutritionist is recommended to ensure a safe and suitable approach to intermittent fasting.

Understanding 16/8 Intermittent Fasting

The 16/8 intermittent fasting method involves dividing your day into two periods: a fasting window of 16 hours and an eating window of 8 hours. During the fasting period, you consume no or minimal calories, while the eating window is dedicated to consuming all your daily calories. In fact, this eating pattern allows your body to utilize stored fat for energy during the fasting period, promoting weight loss.

How 16/8 Intermittent Fasting Aids Weight Loss

  1. Calorie Restriction: The primary reason for weight loss with intermittent fasting is calorie restriction. Hence, by limiting your eating window to 8 hours, you naturally reduce the number of calories consumed throughout the day, leading to a calorie deficit necessary for weight loss.
  2. Hormonal Effects: Intermittent fasting, including the 16/8 method, can positively impact hormones related to weight regulation. During fasting periods, insulin levels decrease, allowing stored fat to be mobilized for energy. Growth hormone levels increase, which helps preserve muscle mass and supports fat burning.
  3. Enhanced Fat Oxidation: With prolonged fasting periods, your body exhausts its immediate glycogen stores and switches to burning fat for fuel. In fact, this process, known as fat oxidation, contributes to weight loss as stored fat is utilized.

Factors Influencing Results of 16/8 Intermittent Fasting 

Several factors can influence how long it takes to see weight loss results with the 16/8 intermittent fasting method. These factors include:

  1. Starting Weight: Individuals with higher initial body weight may experience more rapid weight loss in the early stages of intermittent fasting.
  2. Caloric Intake: While intermittent fasting promotes a calorie deficit, the actual number of calories consumed during the eating window plays a significant role. Therefore, if you consume excessive calories or indulge in unhealthy foods, weight loss may be slower.
  3. Physical Activity: Combining intermittent fasting with regular exercise can accelerate weight loss. Because physical activity helps increase energy expenditure and further enhances fat burning.
  4. Consistency: Consistency is key for seeing results with intermittent fasting. Hence adhering to the 16/8 schedule consistently over time maximizes its benefits for weight loss.

Timeline and Expectations

The timeline for seeing weight loss results with 16/8 intermittent fasting can vary depending on individual factors. However, many individuals usually experience noticeable changes within a few weeks to a couple of months. Here is a general outline:

Weeks 1-2:

During the initial phase, your body adapts to the new eating pattern. You may notice some initial weight loss due to a reduction in water weight and glycogen stores.

Weeks 3-4:

As your body adjusts to the fasting schedule, you may start experiencing more consistent weight loss. Fat burning becomes more prominent, leading to a reduction in body fat percentage.

Months 2 and beyond:

With continued adherence to the 16/8 intermittent fasting method, you can expect steady weight loss. Over time, you may notice improvements in body composition, higher energy levels, and other health benefits associated with weight loss.

It's important to note that everyone's weight loss journey is unique, and individual results may vary. Factors such as genetics, age, and overall health can influence the rate of weight loss.

Conclusion of 16/8 Intermittent Fasting 

16/8 intermittent fasting is a popular approach for weight loss, and the results can vary from person to person. By implementing the 16/8 method consistently and maintaining a calorie deficit, you can expect to see noticeable weight loss within a few weeks to a couple of months. However, it's important to remember that weight loss is a gradual process, and sustainable lifestyle changes are key to long-term success. As with any dietary change, it's advisable to consult with a healthcare professional or registered dietitian to ensure it aligns with your individual needs and goals.


  1. "The effects of intermittent or continuous energy restriction on weight loss and metabolic disease risk markers: A randomized trial in young overweight women." International Journal of Obesity. []
  2. "Effects of Intermittent Fasting on Health, Aging, and Disease." The New England Journal of Medicine. []
  3. "Intermittent fasting: Surprising update." Harvard Health Publishing. []

Note: The sources provided are for informational purposes only, and it is always recommended to consult with a healthcare professional or registered dietitian for personalized advice and guidance on weight loss.

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