Intermittent fasting (IF) is a time- restricted eating pattern. Unlike traditional diets where calories or certain food groups are restricted, IF focuses on when to eat rather than what to eat. The theory behind IF is that by limiting the “eating window” to a specific time frame, your body will have longer periods of time to burn stored fat for energy, ultimately leading to weight loss (1).
As you’ll see, weight loss isn’t the only potential benefit of IF. However, as with any dietary pattern, there are pros and cons to consider before deciding if IF is right for you.
Research that has been done on mostly animal subjects has suggested a number of potential benefits associated with intermittent fasting, including (2) (3) (4):
When you limit your eating to a specific time frame, you’re more likely to consume fewer calories overall. This caloric deficit, possibly coupled with increased fat oxidation, helps shed those unwanted pounds.
IF may enhance your hormone function to facilitate weight loss. For example, it has been seen to increase levels of norepinephrine in rats in the hypothalamus (5), a fat-burning hormone (6), and reduce insulin levels, potentially providing a clearer path for fat to be used as energy (1).
However, it should be noted that not everyone experiences significant weight loss with IF. Individual factors such as lifestyle, diet choices, and adherence to the fasting schedule play crucial roles. Pairing IF with mindful eating habits can further amplify its effectiveness.
Another noteworthy advantage of intermittent fasting is the potential for improved metabolic health. This may mean improved insulin sensitivity and better blood sugar control, which can reduce the risk of type 2 diabetes (7).
During fasting periods, your body reduces insulin production, which allows your cells to use stored fat as fuel. Research has suggested that this shift can lead to lower blood sugar levels and improved insulin sensitivity.
However, as with weight loss, the benefits may not come easily for everyone. Factors such as genetic predispositions or pre-existing health conditions can impede the effectiveness of IF on metabolic health.
Complementing IF with regular physical activity and a balanced diet could help optimize these benefits, making it easier for your body to respond positively to intermittent fasting.
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Intermittent fasting has shown promising potential for enhancing brain function, particularly through its effects on brain-derived neurotrophic factor (BDNF) (8). BDNF is a protein that plays a crucial role in neurogenesis, the process of forming new neurons, and supports cognitive functions such as learning and memory (9). Its levels can decline with age and this loss may be associated with an increased risk of cognitive impairment.
Intermittent fasting has been seen to upregulate BDNF and improve cognitive performance in animals (8).
Fasting also encourages autophagy (10), a natural process where cells clean out damaged components. This helps maintain cellular health and can also reduce the risk of neurodegenerative diseases (11). The potential benefits of enhanced brain function are clear: better focus, improved memory retention, and a lower likelihood of cognitive decline as you age.
To maximize these effects, consider incorporating activities that promote brain health, such as regular exercise, social interactions, and engaging in new learning experiences. This holistic approach can create a supportive environment for your brain to thrive.
Inflammation is a natural response to injury or infection, but chronic inflammation can contribute to various health issues, including heart disease and type 2 diabetes (12). Research has suggested that fasting may lower levels of inflammation, providing a pathway for improved health (13).
During fasting, your body initiates a process called ketosis, where fat becomes the primary source of energy (14). This process produces ketones, which have been suggested to possess anti-inflammatory properties (15). Furthermore, the reduction in insulin and blood sugar levels during fasting may also help decrease systemic inflammation.
The benefits of reduced inflammation are significant; they can enhance overall well-being, reduce chronic pain, and lower the risk of many diseases.
To amplify these benefits, you should consider pairing intermittent fasting with an anti-inflammatory diet rich in whole foods, healthy fats, and plenty of fruits and vegetables (16). This combination can work wonders in maintaining a balanced and healthy lifestyle.
Fasting may have a positive impact on your cardiovascular health (17), which is important as heart disease remains a leading cause of death worldwide (18).
Research has indicated that IF can lower blood pressure, reduce cholesterol levels, and decrease triglycerides (19), all of which are key risk factors for heart disease (20). Weight loss alone can improve these risk factors, which may be how IF does so.
If you’re looking to boost these heart health benefits, consider coupling intermittent fasting with regular aerobic exercise and a heart-healthy diet that is rich in omega-3 fatty acids.
Studies have suggested that caloric restriction, such as that which you find in intermittent fasting, may promote longevity. When your body experiences fasting, it activates cellular repair processes and increases levels of certain hormones that may theoretically delay the aging process (21).
Intermittent fasting has been shown to extend lifespan in animal studies, although research in humans is still ongoing (22). By improving metabolic health and reducing oxidative stress, IF creates an environment that could be conducive to longevity.
Pairing this with a balanced diet and regular physical activity can enhance the potential for a longer life filled with vitality.
Read more: 4-Week Intermittent Fasting: A Complete Guide
Emerging research has suggested that intermittent fasting may have protective effects against certain types of cancer. This is believed to occur due to the reduction in inflammation and the heightened autophagy process during fasting, which helps eliminate damaged cells that could potentially become cancerous (23).
Although more research is required to fully understand these mechanisms, maintaining a healthy lifestyle by avoiding processed meats and alcohol and incorporating plenty of fruits and vegetables could further support these cancer-preventive effects.
While there are potential benefits to intermittent fasting, it’s important to also consider the potential downsides and risks. Here are a few you should keep in mind before you start an intermittent fasting regimen (25) (26):
One common drawback of intermittent fasting is the increase in hunger levels. As your body adjusts to a new eating schedule, you may experience intense cravings, particularly during the initial days. This can be challenging, particularly if you’re transitioning from a traditional meal pattern (26).
To manage this, staying hydrated and incorporating more nutrient-dense, fiber-rich foods during your eating windows can help keep you feeling fuller for longer.
While intermittent fasting can offer health benefits, there’s a risk of nutrient deficiencies if meals aren’t well-planned (27). If you’re not mindful, it’s easy to miss out on essential vitamins and minerals, particularly when eating within a limited time frame.
Ensure you include a variety of foods, focusing on whole grains, lean proteins, fruits, and vegetables. A multivitamin may also help but consult with a healthcare professional first.
If you’re a vegetarian then you’re probably wondering if you can still fast while sticking to your diet? Find out all about Vegetarian Intermittent Fasting in our earlier post.
Fatigue is a potential downside, particularly for those who are unaccustomed to fasting. You may initially feel sluggish or mentally foggy. This often occurs as your body adapts to deriving energy from fat rather than constantly feeding.
It may take a week or two for your energy levels to stabilize. If you find this persists, consider adjusting your eating window or the types of food you consume to boost your energy.
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For some individuals, intermittent fasting can trigger or exacerbate disordered eating behaviors (28). If you’ve had past issues with food, you should be cautious. It may be beneficial to consult a mental health professional or a registered dietitian before you start in order to navigate these risks effectively. It may be better for your health not to fast.
Athletes or those who are heavily into fitness may notice a dip in physical performance during fasting. Energy levels can drop, particularly during long workouts, which makes it harder to maintain intensity. If this concerns you, try timing your workouts during your eating window or adjust your fasting schedule to better support your activity level. If you’re training for an important event, this may not be the time to do intermittent fasting.
Fasting can affect metabolism, particularly if it leads to significant calorie restriction over time. In extreme scenarios, this may cause your body to adapt by slowing down the rate at which you burn energy, which can make losing weight more difficult (29). To mitigate this, you should avoid excessively low-calorie diets and focus on balanced, sensible meals that provide enough energy throughout your eating periods.
There’s a temptation to overindulge during eating windows, particularly after prolonged fasting. This can contribute to unintended weight gain and digestive discomfort (26). To counter this, stick to balanced meals with appropriate portion sizes and be mindful of hunger cues to avoid mindless eating.
Fasting can influence your mood, with some people reporting irritability and mood swings. This reaction can occur due to fluctuations in blood sugar levels, particularly in the initial fasting phases. Staying hydrated, getting enough sleep, and maintaining stable energy through balanced meals when you do eat can help keep your mood in check.
Intermittent fasting isn’t a one-size-fits-all solution. People with certain medical conditions, such as diabetes, should approach it with caution (7). Others, such as pregnant and breastfeeding women, or children and adolescents, shouldn’t fast. Always consult a healthcare provider before making significant dietary changes.
Finally, fasting can pose social challenges, particularly during events focused on food. You may feel out of sync with friends or family who eat at different times. To navigate this, you can plan ahead by communicating your dietary goals or adjusting your fasting schedule for social occasions, which will ensure you don’t miss out on valuable experiences with loved ones.
16 hours is sometimes referred to as the “magic” number for fasting because:
While 16 hours may be the “magic number” for some, it’s important to listen to your body and adjust your fasting schedule accordingly. What works for one person may not work for another, so finding what works best for you is key.
Read more: Intermittent Fasting Weight Loss Plateau: Why it Happens and What to Do
It’s not harmful to do intermittent fasting every day, as long as you:
If you experience any negative side effects or have concerns about the sustainability of intermittent fasting for your lifestyle, it may be best to stop and reassess.
Some signs that indicate it may be time to stop include:
The truth about intermittent fasting is that while it may offer some health benefits, it isn’t suitable for everyone and it’s important to prioritize your overall health and well-being above any dietary trend. If you decide to stop intermittent fasting, there are still many ways you can maintain a healthy lifestyle through mindful eating and regular exercise.
If you’re curious about Intermittent Fasting and Running, check out our previous post to learn more.
After one month of intermittent fasting, you may experience some weight loss and improved metabolic markers such as insulin sensitivity and inflammation (7). You may also notice changes in your eating patterns, such as feeling less reliant on snacking or having a greater appreciation for whole foods. However, individual results may vary, and it’s important to focus on overall health rather than just weight loss when considering the effectiveness of intermittent fasting. Consuming any calories will break a fast. This includes coffee with added milk or sugar. However, black coffee (without any additives) or herbal tea are considered to have minimal impact on the fasting process and can be consumed during fasting periods. Explore healthy Intermittent Fasting Recipes you can try that support your weight loss goals. Yes, this fasting method works for some people. The potential benefits of intermittent fasting 16/8 include weight loss and improving metabolic health. It’s considered to be a relatively manageable fasting schedule for many people and is believed to provide a significant enough period of time without food to reap potential benefits (30). You’re not losing weight on 18:8 fasting because your calorie intake during your eating window may be exceeding your body’s energy needs. It’s important to track your food intake and ensure you’re consuming a balanced amount of nutrients and calories in your meals. Another reason could be that your body has adjusted to the intermittent fasting schedule, and you may need to switch things up by experimenting with longer fasting periods or incorporating strength training into your routine. Breaking intermittent fasting once a week isn’t harmful and may even be beneficial for some individuals. Some types of intermittent fasting, such as the 5:2 method, involve fasting on some days and eating normally on others. These breaks can help prevent feelings of deprivation and make the fasting schedule more sustainable in the long term.Frequently Asked Questions
What happens after 1 month of intermittent fasting?
Does coffee break a fast?
Does 16:8 fasting work?
Why am I not losing weight on 16:8 fasting?
Is it OK to break intermittent fasting once a week?
Intermittent fasting has many potential benefits. It may help with weight loss, improve insulin sensitivity, promote autophagy, and potentially lower the risk of chronic diseases.
However, it also has its downsides. It’s essential to consider these potential negatives before you start intermittent fasting and address them appropriately for a safe and sustainable approach to healthy living.
Consulting a healthcare professional is recommended before making significant dietary changes to ensure it aligns with your individual needs and goals. With careful consideration and proper planning, intermittent fasting can be a useful tool in achieving better overall health and well-being.
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