top of page

Intermittent Fasting:
Techniques and Results


Intermittent fasting (IF) is the name used to describe weight loss strategies involving total or partial fasting for specific periods of time followed by 'normal' eating during other time blocks.  This strategy is very popular as I write this (March, 2023) and has been widely used by many people around the world. On this page, I will present some of the most popular intermittent fasting protocols and then I will also discuss the evidence for and against intermittent fasting for weight loss.

Do NOT attempt intermittent fasting without consulting your health provider. People with diabetes are especially sensitive to changes in eating patterns because they will likely need to adjust their medication dosage(s) and timing to compensate for the huge shifts in carbohydrate burden that IF causes. It is essential that you do not undertake IF on your own.

Does it Work?
As you will see below and as is typical for nearly all lifestyle interventions, it is not easy to tell how well IF actually works and how it compares to other weight loss strategies. My impression  as a weight loss physician is that IF does work but it may not be any easier or less unpleasant than direct calorie counting.  It may sound pretty easy to fast for long periods regularly, but it usually is not, especially initially.  But for some people, IF has worked well and they claim that it is relatively painless.  In my experience though, this is fairly uncommon and most people don't care for IF and choose other less harsh techniques. Still, people are different and for some, IF may be an excellent approach.

Popular Intermittent Fasting

Protocols for Weight Loss


Intermittent fasting (IF) has gained popularity as a weight loss strategy due to its potential benefits and flexibility. Various IF protocols have emerged, each with its unique approach to fasting and feeding periods. This essay will describe five popular intermittent fasting protocols for weight loss, highlighting their key characteristics and potential advantages.

The 16/8 Method (Leangains Protocol)

The 16/8 method, also known as the Leangains Protocol, involves fasting for 16 consecutive hours each day and eating within an 8-hour window. This protocol is relatively easy to adopt, as the fasting period often includes sleep, which accounts for about 7-8 hours of the fast. The remaining hours can be tailored around individual schedules and preferences.

For example, an individual may choose to skip breakfast and have their first meal at noon, followed by their last meal at 8 pm. During the 8-hour eating window, individuals can consume two to three meals and are encouraged to prioritize protein intake and nutrient-dense foods.

The 16/8 method is popular because it is relatively easy to follow and can be adapted to fit most lifestyles. It has been associated with improvements in insulin sensitivity, metabolic rate, and weight loss (Tinsley & La Bounty, 2015).

The 5:2 Method (Fast Diet)

The 5:2 method, also known as the Fast Diet, involves eating normally for five days of the week and restricting caloric intake to about 500-600 calories for the other two non-consecutive days. For example, an individual may choose to eat normally from Monday to Friday and fast on Saturday and Sunday, or select any other two non-consecutive days for fasting.

During fasting days, individuals can consume small meals or snacks that are high in protein and fiber to help manage hunger. The 5:2 method has been shown to promote weight loss and improve metabolic health (Harvie et al., 2011).

Alternate-Day Fasting (ADF)

Alternate-day fasting (ADF) involves alternating between fasting days, where individuals consume little to no calories, and non-fasting days, where they can eat ad libitum (without restriction). For example, an individual may fast on Monday, Wednesday, and Friday, and eat normally on the other days of the week.

Some variations of ADF allow for the consumption of up to 500 calories on fasting days to help manage hunger and adherence. Studies have demonstrated that ADF can lead to significant weight loss and improvements in cardiovascular and metabolic health markers (Varady, 2011).

Eat Stop Eat

Eat Stop Eat is an intermittent fasting protocol developed by Brad Pilon. It involves one or two 24-hour fasts per week, with no specific restrictions on the remaining days. For example, an individual may choose to fast from dinner on Tuesday to dinner on Wednesday and then again from dinner on Friday to dinner on Saturday.

During the 24-hour fasting periods, individuals can consume calorie-free beverages such as water, tea, or black coffee. The Eat Stop Eat protocol has been shown to promote weight loss and improve metabolic markers (Heilbronn et al., 2005).

The Warrior Diet

The Warrior Diet, created by Oriler, is based on the concept of eating minimally during the day and consuming a large meal at night. This protocol involves a 20-hour fasting period followed by a 4-hour eating window, typically in the evening. During the fasting period, individuals are encouraged to consume small amounts of nutrient-dense foods such as fruits, vegetables, and protein-rich snacks, while the main meal should be well-balanced and nutrient-rich.

The Warrior Diet is inspired by the eating patterns of ancient warriors, who supposedly consumed their meals at night after a day of physical activity. While there is limited scientific evidence specifically supporting the Warrior Diet, the protocol shares similarities with other IF methods that have shown benefits for weight loss and metabolic health (Hofmekler, 2007).


Intermittent fasting has become a popular weight loss strategy due to its flexibility and potential health benefits. The five protocols discussed in this essay – the 16/8 method, the 5:2 method, alternate-day fasting, Eat Stop Eat, and the Warrior Diet – offer various approaches to fasting and feeding periods, allowing individuals to choose the method that best suits their lifestyle and preferences.

While these popular IF protocols have shown promising results in terms of weight loss and metabolic health, it is important to note that individual responses may vary, and the long-term effectiveness and safety of each protocol are yet to be fully established. Consulting with a healthcare professional before embarking on an intermittent fasting plan is recommended to ensure the chosen method is suitable for an individual's specific needs and circumstances.

Intermittent Fasting for Weight Loss:

The Evidence For and Against


Intermittent fasting (IF) is a popular dietary approach that involves alternating periods of eating and fasting. In recent years, there has been an increasing interest in the potential health benefits of intermittent fasting for weight loss. This essay will explore the evidence for and against intermittent fasting as a strategy for human weight loss, focusing on studies and expert opinions, as well as the implications of hunger on this dietary approach.

Part 1: The Evidence For Intermittent Fasting

1.1 Improved Insulin Sensitivity

One of the main benefits of intermittent fasting is its impact on insulin sensitivity, which is closely related to weight loss. Studies have shown that IF can improve insulin sensitivity, allowing the body to use glucose more efficiently and reduce the risk of developing type 2 diabetes (Varady, 2011). Improved insulin sensitivity also helps promote weight loss by encouraging the body to use stored fat for energy.

1.2 Increased Fat Burning and Metabolic Rate

Intermittent fasting can also help increase fat burning and metabolic rate. When the body is in a fasted state, it shifts from utilizing glucose to burning fat for energy. This switch to fat metabolism is believed to be a key mechanism behind the weight loss benefits of IF (Mattson et al., 2017). Additionally, some studies have suggested that IF can increase resting energy expenditure, which may contribute to weight loss by increasing the number of calories burned (Heilbronn et al., 2005).

1.3 Hormonal Adaptations

Intermittent fasting has been shown to influence various hormones that play a role in weight regulation, such as ghrelin, leptin, and adiponectin. For example, IF has been associated with decreased levels of the hunger hormone ghrelin, potentially reducing appetite and facilitating weight loss (Cummings et al., 2004). Moreover, IF has been shown to increase levels of adiponectin, which is associated with improved insulin sensitivity and reduced inflammation, both of which can promote weight loss (Varady, 2011).

1.4 Long-term Sustainability and Adherence

A key advantage of intermittent fasting over other weight-loss diets is its long-term sustainability. Many traditional calorie-restricted diets can be difficult to maintain, leading to weight regain over time. In contrast, intermittent fasting may be easier to stick to, as it often allows for greater flexibility in food choices and meal timing, which may lead to better adherence and more sustainable weight loss (Varady, 2011).

Part 2: The Evidence Against Intermittent Fasting

2.1 Lack of Long-term Studies

One of the primary arguments against intermittent fasting as a weight loss strategy is the lack of long-term studies. Most research on IF has been conducted over relatively short periods (a few weeks to a few months). Therefore, it is difficult to draw conclusions about the long-term effectiveness and safety of IF for weight loss (Trepanowski & Bloomer, 2010).

2.2 Variability in Intermittent Fasting Protocols

There is a wide variety of intermittent fasting protocols, which can make it challenging to determine the most effective approach for weight loss. Some popular IF protocols include the 16/8 method, the 5:2 method, and alternate-day fasting. The effectiveness of each protocol may vary depending on the individual, and there is no one-size-fits-all solution (Patterson & Sears, 2017).

2.3 Potential Negative Effects on Hormones and Metabolic Rate

While some studies suggest that intermittent fasting can improve hormonal balance and metabolic rate, others have reported potential negative effects. For example, some research has shown that fasting can lead to decreased levels of thyroid hormones, which may slow down the metabolism and make weight loss more difficult (Mansell et al., 1990). Additionally, prolonged fasting may increase cortisol levels, which can promote fat storage and negate some of the weight loss benefits associated with IF (Knutson et al., 2007).

2.4 Risk of Overeating and Compensatory Eating

One potential drawback of intermittent fasting is the risk of overeating during non-fasting periods. Some individuals may compensate for the reduced caloric intake during fasting periods by overeating during their feeding window, negating the potential weight loss benefits of IF (Anton et al., 2018). This compensatory eating behavior may vary between individuals and could undermine the overall effectiveness of IF as a weight loss strategy.

Part 3: Hunger and Intermittent Fasting

3.1 Hunger During Fasting Periods

Hunger is a common concern for individuals considering intermittent fasting. During the initial stages of IF, many people may experience increased hunger due to the body's natural response to reduced caloric intake. However, studies have shown that hunger levels tend to decrease over time as the body adapts to the fasting regimen (Johnstone, 2015).

3.2 Adaptation to Fasting and Hunger Management

As individuals continue to practice intermittent fasting, their bodies may undergo several physiological adaptations that help manage hunger. For example, as mentioned earlier, IF can lead to decreased levels of the hunger hormone ghrelin, potentially reducing appetite over time (Cummings et al., 2004). Additionally, the body may become more efficient at utilizing stored fat for energy during fasting periods, which can help alleviate hunger and maintain energy levels (Mattson et al., 2017).

3.3 Strategies to Manage Hunger

There are several strategies that individuals can use to manage hunger while practicing intermittent fasting:

  • Drinking water, tea, or black coffee during fasting periods can help suppress appetite and maintain hydration.

  • Consuming fiber-rich, nutrient-dense foods during feeding windows can promote satiety and help prevent overeating.

  • Engaging in physical activity or mindfulness techniques, such as meditation, can help divert attention from hunger and promote a sense of well-being.


In summary, intermittent fasting has shown promising results as a weight loss strategy, with benefits including improved insulin sensitivity, increased fat burning, and favorable hormonal adaptations. However, there are concerns regarding the lack of long-term studies, variability in fasting protocols, potential negative effects on hormones and metabolic rate, and the risk of overeating.

Hunger is a common concern associated with intermittent fasting. While initial hunger may be challenging, the body tends to adapt over time, and several strategies can be employed to manage hunger effectively. Further research is needed to establish the long-term effectiveness and safety of intermittent fasting, as well as to determine the most appropriate fasting protocols for different individuals.

  1. Varady, K. A., & Hellerstein, M. K. (2007). Alternate-day fasting and chronic disease prevention: a review of human and animal trials. The American Journal of Clinical Nutrition, 86(1), 7-13. This review article examined human and animal trials investigating the effects of alternate-day fasting on weight loss and chronic disease prevention. The authors concluded that alternate-day fasting could be an effective weight loss strategy and might provide additional health benefits, such as improved cardiovascular and diabetes risk factors.

  2. Harvie, M. N., Pegington, M., Mattson, M. P., Frystyk, J., Dillon, B., Evans, G., ... & Howell, A. (2011). 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, 35(5), 714-727. This randomized trial compared the effects of intermittent energy restriction (a form of intermittent fasting) to continuous energy restriction (traditional daily calorie restriction) in 107 overweight or obese premenopausal women. After six months, both groups experienced similar weight loss, but the intermittent fasting group had greater improvements in insulin sensitivity.

  3. Tinsley, G. M., & La Bounty, P. M. (2015). Effects of intermittent fasting on body composition and clinical health markers in humans. Nutrition Reviews, 73(10), 661-674. This review examined the effects of intermittent fasting on body composition and clinical health markers in humans. The authors concluded that intermittent fasting could be an effective weight loss strategy and might provide additional health benefits, such as improved blood lipid profiles and reduced inflammation.

  4. Seimon, R. V., Roekenes, J. A., Zibellini, J., Zhu, B., Gibson, A. A., Hills, A. P., ... & Sainsbury, A. (2015). Do intermittent diets provide physiological benefits over continuous diets for weight loss? A systematic review of clinical trials. Molecular and Cellular Endocrinology, 418, 153-172. This systematic review analyzed the effects of intermittent fasting on weight loss and metabolic health in 40 clinical trials. The authors found that intermittent fasting was as effective as continuous calorie restriction for weight loss, with some evidence suggesting potential additional benefits for glucose control and insulin sensitivity.

  5. Trepanowski, J. F., Kroeger, C. M., Barnosky, A., Klempel, M. C., Bhutani, S., Hoddy, K. K., ... & Varady, K. A. (2017). Effect of alternate-day fasting on weight loss, weight maintenance, and cardioprotection among metabolically healthy obese adults: a randomized clinical trial. JAMA Internal Medicine, 177(7), 930-938. This randomized clinical trial compared the effects of alternate-day fasting and daily calorie restriction on weight loss, weight maintenance, and cardioprotection in 100 metabolically healthy obese adults. After six months, both groups experienced similar weight loss, but the alternate-day fasting group had slightly higher dropout rates

bottom of page