Intermittent fasting (IF) is a type of eating plan that has existed for centuries. It’s rooted in many religions and cultures but has been adapted to the modern world due to its numerous health benefits. In its simplest terms, IF is a pattern of eating that alternates between periods of fasting and eating. Unlike traditional diets that focus on WHAT you eat, intermittent fasting emphasizes WHEN you eat. This approach doesn’t necessarily specify certain foods to eat, but instead, you cycle through specific periods of voluntary abstinence from food and drink. 

In recent years, IF has skyrocketed in popularity, catching the attention of not only health enthusiasts but also researchers and clinicians. This surge in popularity is due to its simplicity, the flexibility of its methods, and a growing body of scientific evidence suggesting potential health benefits. Some of these range from weight loss and improved metabolic health to enhanced brain function and longevity. You might be wondering whether IF is right for you. So, let’s dive in and discuss everything there is to know before embarking on this new pattern of eating.

The Science Behind Intermittent Fasting

The sole purpose of IF is to reprogram the body’s metabolic process. When you fast, the body undergoes several cellular and molecular changes. Key hormones involved in metabolism, like insulin and norepinephrine, are significantly impacted. During fasting periods, insulin levels drop dramatically. When this happens, fat-burning ramps up. This reduction in insulin5 is beneficial because high insulin levels prevent fat breakdown. At the same time, levels of norepinephrine increase, which can also enhance fat burning by boosting your metabolic rate. Research suggests2 that following this pattern of eating has allowed individuals to lose weight, feel more energized, and experience fewer cravings.

But the benefits of IF extend far beyond just weight management. Emerging research3 suggests that this eating pattern can lead to improved brain health. This is partly attributed to the production of brain-derived neurotrophic factor (BDNF), a protein that plays a role in neuron survival and growth during fasting states1. Enhanced BDNF levels can lead to improved cognitive function and resistance to neurodegenerative diseases.

Additionally, IF has shown promise in reducing inflammation, which is a key driver of many chronic diseases. This reduction in inflammation can have widespread health implications, potentially lowering the risk of chronic conditions like type 2 diabetes, heart disease, and certain cancers. 

Different Types of Intermittent Fasting

IF is not a one-size-fits-all approach. There are several different methods of IF, each with its own unique set of principles. One type of fasting method may work great for someone, but not as well for someone else. Let’s review the main features of the different IF methods to help you better determine which one sounds right for you. However, it’s important to remember that while intermittent fasting can be beneficial, it’s not suitable for everyone (more on that later). 

Time-Restricted Eating

The most common time-restricted eating plan is the 16/8 method. This method involves fasting for 16 hours each day and eating all your food within an 8-hour window. For example, you might eat between 12 pm and 8 pm, then fast until noon the next day. This method is popular for its simplicity and ease of adherence. It’s particularly suitable for those new to fasting. Within this 8-hour window, you can fit in 2 or 3 meals. 

The 5/2 Diet

The 5/2 approach involves eating normally for five days of the week and then reducing your calorie intake to about 500-600 calories on the other two days. These two fasting days are not meant to be consecutive. This is a more flexible approach to fasting, allowing a normal diet most of the time while still reducing overall calorie intake. 

Eat-Stop-Eat

The Eat-Stop-Eat approach involves a full 24-hour fast once or twice a week. For example, if you finish dinner at 7 pm, you wouldn’t eat again until 7 pm the following day. This method can be more challenging due to the longer fasting period, but it allows for a normal eating pattern on non-fasting days.

Alternate-Day Fasting

This method involves alternating days of normal eating with days where you either completely fast or consume a very small amount of calories (around 500). It’s a more intense form of fasting, and research suggets4 that it might not contribute to weight loss any more than traditional daily calorie restriction.

Warrior Diet

The warrior diet is based on the eating patterns of ancient warriors. It technically doesn’t include much fasting, but it involves eating small amounts of fruits and vegetables throughout the day and then eating one large meal at night within a 4-hour eating window. This diet emphasizes food choices that are high in nutrients and low in calories during the day, with more freedom during the evening meal.

Tips for Starting Intermittent Fasting

Embarking on your intermittent fasting journey can be both exciting and challenging. To help you start off on the right foot, here are some essential tips:

  • If you’re new to IF, it’s important to ease into it. Start with a shorter fasting window and gradually extend it. For instance, begin with a 12-hour fast and slowly increase the duration to 16 hours over a few weeks. This gradual increase helps your body adjust without significant stress or discomfort.
  • Hydration is key during fasting periods. Water is essential, but you can also include non-caloric beverages like herbal teas or black coffee. These can help manage hunger pangs and keep you feeling full. Remember, staying hydrated also boosts metabolism and helps curb appetite.
  • During your eating windows, prioritize nutrient-dense foods. This means meals rich in fiber, protein, and heart-healthy fats. Opt for whole foods like vegetables, fruits, lean proteins, whole grains, oils, nuts, and seeds. These foods not only provide essential nutrients but also keep you satiated longer, which will make fasting periods easier. 
  • Pay close attention to how your body reacts to IF. It’s normal to feel a bit hungry initially, but be alert for signs of fatigue, dizziness, or excessive hunger. If you experience adverse effects, reconsider the fasting method or duration. The goal is to find a balance where you can maintain fasting without compromising your well-being.

Common Challenges and How to Overcome Them

Adopting intermittent fasting (IF) can present several challenges, but with the right strategies, these can be managed effectively. Let’s take a look at some of these:

  • Hunger and Cravings: It’s normal to experience hunger and cravings, especially in the early stages of IF. To manage these, try drinking water or herbal teas. Sometimes, what feels like hunger is actually thirst. Also, ensure your meals are balanced with plenty of protein, fiber, and healthy fats, which are more satiating.
  • Social Events and Dining Out: Socializing while on IF can be tricky. If possible, schedule your eating window around these events. If that’s not feasible, remember that occasional exceptions won’t derail your progress! 
  • Maintaining Energy Levels: Some people experience dips in energy when they start IF. To combat this, focus on nutrient-dense foods during your eating periods to ensure you’re fueling your body adequately. If you’re feeling sluggish, a light, low-intensity workout or a short walk can help boost your energy levels.
  • Dealing with Potential Side Effects: Side effects like headaches or irritability are common when beginning IF. These often result from dehydration or electrolyte imbalances, so staying hydrated is especially critical. Additionally, incorporating a small amount of salt into your diet can help manage electrolyte balance. If side effects are severe or persistent, consider adjusting your fasting schedule or consulting a healthcare professional.

How Do I Exercise During Intermittent Fasting?

You might be wondering, how can I possibly get a proper workout in when I’m undergoing a fast? Well, you’re not alone – many people who started fasting have thought the same thing. Integrating exercise into your IF regimen requires some strategy, particularly regarding timing. Many people find it beneficial to schedule workouts towards the end of their fasting period. This timing allows you to exercise when your body is primed to burn fat more efficiently and then refuel with your first meal post-workout, which aids in recovery and muscle synthesis.

However, it’s worth noting that your exercise performance might initially decrease as your body adjusts to the new eating pattern. During the early stages of IF, some people experience reduced energy levels, which, of course, can impact workout intensity. But typically, the body adapts over time! As you become more accustomed to IF, you’ll likely notice your energy levels and exercise performance returning to normal or even improving.

Who Should Avoid Intermittent Fasting?

Intermittent fasting is certainly not suitable for everybody. Certain groups should avoid IF or approach it with caution. This includes pregnant and breastfeeding women. Fasting could impact the necessary nutrient intake for both the mother and the developing baby. Individuals with a history of eating disorders should also avoid this way of eating, as IF could potentially trigger unhealthy eating patterns.

People with certain medical conditions, particularly those that involve blood sugar regulation, such as diabetes, should be careful. Fasting can affect blood sugar levels, so individuals with diabetes or hypoglycemia need to manage these conditions closely if considering IF. Similarly, those with a history of heart conditions should consult a healthcare professional, as fasting can impact blood pressure and heart rate.

Given these considerations, it’s recommended to consult with a healthcare provider before starting an IF regimen, especially if you have any preexisting conditions.

The Bottom Line

Intermittent fasting stands out as a powerful approach to eating that goes beyond traditional dieting. Instead of focusing so much on the exact foods and quantities you eat, it focuses on the timing of eating. Its benefits, ranging from weight loss and improved metabolic health to enhanced cognitive function and potential longevity, have made this way of eating extremely desirable for so many. 

The true essence of IF lies in its flexibility and adaptability to different lifestyles and preferences. If you decide to try fasting, remember that it’s not one-size-fits-all. There are many different methods you can explore, and they can each be tailored to fit your needs. Listen to your body, adjust your approach as needed, and most importantly, ensure that your choice fits comfortably within your lifestyle and health goals.

  1. Bathina, S., & Das, U. N. (2015). Brain-derived neurotrophic factor and its clinical implications. Archives of medical science : AMS, 11(6), 1164–1178. https://doi.org/10.5114/aoms.2015.56342
  2. Elsworth, R. L., Monge, A., Perry, R., Hinton, E. C., Flynn, A. N., Whitmarsh, A., Hamilton-Shield, J. P., Lawrence, N. S., & Brunstrom, J. M. (2023). The Effect of Intermittent Fasting on Appetite: A Systematic Review and Meta-Analysis. Nutrients, 15(11), 2604. https://doi.org/10.3390/nu15112604
  3. Seidler, K., & Barrow, M. (2022). Intermittent fasting and cognitive performance – Targeting BDNF as potential strategy to optimise brain health. Frontiers in Neuroendocrinology, 65, 100971. https://doi.org/10.1016/j.yfrne.2021.100971
  4. Trepanowski, J. F., Kroeger, C. M., Barnosky, A., Klempel, M. C., Bhutani, S., Hoddy, K. K., Gabel, K., Freels, S., Rigdon, J., Rood, J., Ravussin, E., & 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. https://doi.org/10.1001/jamainternmed.2017.0936
  5. Yuan, X., Wang, J., Yang, S., Gao, M., Cao, L., Li, X., Hong, D., Tian, S., & Sun, C. (2022). Effect of Intermittent Fasting Diet on Glucose and Lipid Metabolism and Insulin Resistance in Patients with Impaired Glucose and Lipid Metabolism: A Systematic Review and Meta-Analysis. International journal of endocrinology, 2022, 6999907. https://doi.org/10.1155/2022/6999907