Intermittent fasting (IF) has grown in popularity, often praised for its potential weight loss benefits and claims of improved health. It’s understandable why many people are drawn to it—living in a society that equates thinness with health can make methods like intermittent fasting seem appealing. But is it really the miracle solution it’s often portrayed to be? In this article, we’ll explore the nuances of intermittent fasting, look at its true effects, weigh the potential benefits against the risks, and discuss whether it’s a healthy, sustainable way to approach eating.
What is Intermittent Fasting?
Intermittent fasting (IF) is an eating pattern that alternates between periods of eating and fasting. It doesn’t focus on what foods you should eat, but rather when you should eat. Popular methods include:
• 16/8 method: Fasting for 16 hours and eating during an 8-hour window.
• 5:2 method: Eating normally for five days and drastically reducing intake (about 500–600 calories) for two non-consecutive days.
• Alternate-day fasting: Alternating between eating normally one day and fasting the next.
How Does Intermittent Fasting Work?
The theory behind intermittent fasting is that by extending the time between meals (from 14 hours up to 1-2 days), your body is forced to tap into stored fat for energy, leading people to hope for fat loss. IF supporters claim that in the fasted state, the body turns to fat for fuel (instead of carbohydrates from food).
While this mechanism might sound promising, the reality is much more complex. The body doesn’t instantly switch to burning fat when fasting. It can use glycogen (stored glucose from carbohydrates) for energy, can convert amino acids from muscle protein for energy and can use some fat for energy. Even then, this doesn't mean you'll automatically lose weight from burning fat during a fast—weight loss depends more on overall caloric intake (as well as genetics, sleep, stress, medication usage, dieting history, etc) compared to what type of fuel your body is using.
Moreover, even in a non-fasting state, our bodies actually use fat for fuel throughout the day anyway. We’ll be using more fat than glucose for fuel during low impact sports – or even sitting down and watching tv. So, while fasting may push your body to use some more fat for energy, it doesn’t flip a simple switch from burning glucose to fat, and that mechanism typically doesn’t cause weight loss anyway.
Weight Loss and Intermittent Fasting
A common reason people turn to intermittent fasting is the promise of weight loss. And in a weight-obsessed culture, it’s easy to see why people feel pressure to try it. Studies have shown that intermittent fasting can result in short-term weight loss, but this is largely due to caloric restriction, not the fasting itself (1). When you limit your eating window, it can be harder to eat the same amount, resulting in a caloric deficit.
However, these results are often temporary. Weight tends to return within months or years, with some people gaining back more than they initially lost. This happens for several reasons:
Metabolic Adaptations: Over time, intermittent fasting can slow your metabolism. When the body experiences irregular or limited food intake, it conserves energy by burning fewer calories. This natural survival mechanism can counteract any initial weight loss and may lead to weight gain when regular eating resumes (2).
Altered Hunger Cues: Long fasting periods may disrupt your natural hunger signals. After fasting, many people feel the urge to eat larger meals because hunger regulation becomes less reliable. This can lead to overeating during feeding windows, potentially wiping out any calorie deficit (3).
Psychological Effects: The restrictive nature of intermittent fasting can lead to feelings of deprivation, causing some people to enter into cycles of bingeing and restricting. This can create a cycle of guilt, shame, and frustration around food. Over time, this can harm both mental and physical health (4).
Is Intermittent Fasting Easy to Stick To?
For many people, sustainability is a significant challenge with intermittent fasting. The initial transition can be tough, especially for those used to eating more frequently, early in the morning or late at night. In the beginning, people often experience fatigue, irritability, and difficulty concentrating due to hunger during the fasted hours. Although these hunger signals may diminish over time, this doesn’t mean the body no longer needs food—it’s simply an adaptation to conserve energy. This can lead people to override their body’s natural hunger signals, which may not be supportive of long-term health.
Additionally, IF can impact social life and mental well-being. Many social gatherings revolve around food, and rigid fasting schedules may make people skip meals, avoid eating out, or feel isolated. This can leave people feeling disconnected from the joy and community that often come with shared meals. For many, intermittent fasting just isn’t realistic in a world where life doesn’t always follow strict schedules.
Impact on Exercise Performance and Muscle Mass
Exercising while fasting is possible, but it’s generally not recommended for high-intensity activities like strength training or cardio. Carbohydrates are the body’s preferred energy source for such workouts, and fasting can reduce performance due to low energy availability (5). Being well-fueled will typically help with strength, endurance, or just feeling good while moving – however, if you personally feel better doing a fasted workout, that’s perfectly fine.
Some people believe fasted workouts lead to more fat burning. While it’s true that you might burn more fat during the workout itself, this doesn’t necessarily lead to greater fat loss overall, as we discussed previously. Without enough fuel, you might not be able to sustain the same intensity you’d have if you ate beforehand. Additionally, fasting can impair muscle recovery, as amino acids from protein are essential for muscle repair.
The Health Implications of Intermittent Fasting
Intermittent fasting has been linked to various health benefits, including improved insulin sensitivity, better blood sugar control, and reduced cholesterol and blood pressure. Unfortunately, most studies are short-term or have inconsistent findings, making it hard to draw definitive conclusions. Plus, if intermittent fasting is hard to stick to, the potential benefits would likely be temporary as well.
Beyond physical health, intermittent fasting can impact your relationship with food. Repeatedly ignoring your hunger cues can make it harder to connect with your body’s natural signals, which are essential for knowing how much to eat. Many people report feeling out of touch with when and how much to eat after fasting for long periods, which can make it harder to develop a balanced, healthy relationship with food. This disconnection can contribute to overeating or binge eating as well, as discussed earlier.
It’s also important to recognize the mental and emotional toll that intermittent fasting can take. The stress of maintaining a rigid eating schedule, combined with societal pressures around weight, can negatively affect well-being, particularly in social settings where food is a key element of connection.
Conclusion: Is Intermittent Fasting Worth It?
In my opinion, intermittent fasting is likely not worth the trouble for most people. While it may offer some short-term weight loss and health benefits, these effects are often temporary and come with significant physical, psychological, and social drawbacks. In a world that glorifies dieting and weight loss, it can feel tempting to turn to methods like intermittent fasting, but this approach may leave you feeling more restricted and disconnected from your body. That said, some people naturally find it easy to skip breakfast—such as doing a 14-hour fast from 10 p.m. to noon—and feel better for it. If this works well for you, there's likely no harm in continuing. I’d simply encourage you to try eating in the morning occasionally to see if it provides more energy.
I believe that the best approach to health is one that’s sustainable and helps you foster a healthy, trusting relationship with food. If intermittent fasting feels like another diet (something you could only do for a few weeks or a few months) or leads to feelings of guilt, stress, or deprivation, it’s probably not the right fit for you. Instead, consider a more balanced, flexible approach to eating—one that honors your body’s hunger and fullness cues, supports your well-being, and leaves room for enjoyment and satisfaction.
Final Thoughts
I hope this article has provided valuable insight into the realities of intermittent fasting. If you have more questions or would like to work on your habits and relationship with food, remember that you don’t have to navigate it alone. Seeking support from a registered dietitian can be a great way to develop a healthier relationship with food that’s rooted in well-being, not weight.
For those in Quebec, feel free to reach out to schedule a discovery call or connect with me via email. I’m here to help support you on your journey to better health!
You can also listen to more on this topic on my podcast, "Wellness Debunked," where I explore intermittent fasting and fasted workouts with Kinesiologist Gabe Marcogliese. Search for "Wellness Debunked" on Spotify or Apple Podcasts to tune in or click on the link below:
Spotify: https://lnkd.in/eCjtsbUn
Apple Podcasts: https://t.ly/wTWr-
References:
1. Trepanowski, J. F., et al. (2017). "Effects of Alternate-Day Fasting or Daily Calorie Restriction on Body Composition, Fat Distribution, and Glucose Regulation in Obese Adults." JAMA Internal Medicine, 177(7), 930-938. doi:10.1001/jamainternmed.2017.0936.
2. Speakman, J. R., & Hambly, C. (2016). "Body size, energy metabolism and lifespan." Journal of Experimental Biology, 219(Pt 10), 1444-1456. doi:10.1242/jeb.125500.
3. Longo, V. D., & Mattson, M. P. (2014). "Fasting: Molecular mechanisms and clinical applications." Cell Metabolism, 19(2), 181-192. doi:10.1016/j.cmet.2013.12.008.
4. Stice, E., Durant, S., Rohde, P., & Shaw, H. (2016). "Increased risk of binge eating disorder and weight gain following exposure to weight loss treatment." Journal of Consulting and Clinical Psychology, 84(2), 174-182. doi:10.1037/ccp0000043.
5. Hevia-Larraín, V., et al. (2021). "Effect of Alternate Day Fasting on Markers of Cardiovascular Risk in Physically Active Adults." Frontiers in Physiology, 12, 634720. doi:10.3389/fphys.2021.634720.
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