When it comes to weight loss, there are few topics more popular than intermittent fasting.
Many argue that it cracks the weight loss code in ways that other diets don’t.
The skeptics, on the other hand, think it’s overhyped.
In this article, we’ll explore the topic of intermittent fasting and weight loss from multiple angles. We’ll explain how it works and discuss when and for whom it may not be effective. By the end, you’ll have the information you’ll need to decide if intermittent fasting can help you reach your weight loss goals or not.
But before we dive into intermittent fasting as a weight loss strategy, we must first understand how weight loss works.
Caution: Fasting is not for everyone, especially those who are pregnant or breastfeeding, under the age of 18, or have diabetes, low blood pressure, or a history of eating disorders. Please consult your doctor before starting a fasting practice.
Intermittent Fasting and Weight Loss: How Weight Loss Works
There’s no way around it: if you want to lose weight, you need to put yourself into a caloric deficit. In other words, you need to consume fewer calories than you burn.
It sounds simple, but successfully achieving a caloric deficit is much more complex than “eat less, move more.” That’s because there are other considerations beyond counting calories, restricting food choices, and strengthening will power.
The different factors that affect weight loss include:
- Health status
- Metabolic rate
- Food quality and macronutrient composition...
These factors influence things like appetite, satiety, energy levels, and other things that ultimately determine caloric intake, the number of calories absorbed, and the amount and rate at which calories are burned.
On the surface, weight loss is basic math. But in practice, getting to a caloric deficit requires the coordination of many interdependent systems.
You don’t need a Ph.D. in Complex Systems to successfully lose weight, but it does help to know that a lot more goes into it than many realize.
And the weight loss strategy that ultimately works for you will be the one that accounts for your body’s complexity and gives you direct control over your ability to achieve a caloric deficit.
And this brings us to intermittent fasting. Is this health trend the key that can unlock your weight loss?
You’ve heard how it works wonders for some and not so well for others. But you want to know if it can work for you. And since the answer depends on a lot more than math, let’s examine what intermittent fasting is, how it works, its potential advantages, and its limitations.
How Intermittent Fasting Works for Weight Loss
Intermittent fasting (IF), also known as time-restricted feeding, is less of a “diet” and more of an eating schedule.
Instead of restricting food type and quantity, it structures your eating around feasting and fasting windows.
For example, a 16:8 intermittent fast involves a 16 hour fast followed by an 8 hour period during which you consume all of your daily calories. The windows’ timing is up to you, and the length of the fasting and feasting windows can vary. Other popular variations include 13:11, 18:16, and 20:4.
In principle, by shortening your eating window, you can better control and ultimately reduce your caloric intake.
Sounds good, but what does the research say?
The Research on Intermittent Fasting and Weight Loss
According to a 2014 review study, intermittent fasting can cause 3–8% weight loss over 3–24 weeks . Other studies also show that intermittent fasting results in weight loss but to a much smaller degree .
While many animal studies show promising and dramatic results, more research on humans is needed.
Although intermittent fasting is an effective weight loss strategy, it’s unclear if it’s better than other weight loss strategies focusing on caloric restriction .
But Doesn’t Intermittent Fasting Have a "Metabolic Advantage" Over Other Weight Loss Methods?
The lack of research doesn’t stop many from claiming that intermittent fasting creates a special metabolic environment that gives it an edge over other weight loss diets.
For example, intermittent fasting has been shown to increase plasma levels of norepinephrine, which can elevate metabolic rate by 3.6–14%, contributing to a caloric deficit by way of increasing calories burned .
Intermittent fasting also increases Human Growth Hormone (HGH), which can help stave off the muscle loss that is often associated with weight loss and improves insulin levels, making body fat more available for fuel .
However, some studies comparing intermittent fasting to caloric restriction show no difference in net weight loss between methods.
This suggests that intermittent fasting’s effect on metabolism and hormones, while having other potential health benefits, doesn’t pay extra dividends when it comes to weight loss .
How Does Intermittent Fasting Work for Weight Loss?
Despite this, intermittent fasting does have other advantages for weight loss. Chief among them is simplicity and ease.
Many diets strive to reduce caloric intake by restricting calories (by way of calorie counting) and limiting food choices.
Intermittent fasting, on the other hand, only requires that you keep track of time. For many, intermittent fasting is less stressful and time-consuming than traditional calorie-counting.
As a result, it can be adapted to fit a range of lifestyles and is easier to introduce and sustain than traditional diets.
Additionally, when done mindfully, intermittent fasting can improve self-awareness. Mindful fasters learn to ride the waves of hunger and discern between psychological hunger and physiological hunger. With increasing self-control, you can resist the impulse to indulge in emotional eating and make healthier choices that support your weight loss goals.
In sum, intermittent fasting is a novel way to make weight loss easier. By limiting your eating window, you create conditions that make it easier to consume fewer calories and sustain a caloric deficit.
But it takes more than “the right conditions” to lose weight with intermittent fasting, and even those that stick to their fasting schedule may not see any results.
To help explain why let’s cover the three most common reasons people struggle to lose weight with intermittent fasting.
Why Am I Not Losing Weight With Intermittent Fasting?
Reason #1: You’re a Premenopausal Woman
Women often see men lose weight with intermittent fasting and think it’ll work for them, too. And while fasting can absolutely be helpful for some women, it may not work for others. In fact, it may even be detrimental to their health.
What you can do: Learn more about what the research tells us, why fasting affects women differently than men, and how to determine if fasting is right for you by reading part 1 and part 2 of our series titled The Complete Guide to Fasting for Women.
Reason #2: You’re Overeating During Your Feeding Window
Many who struggle to lose weight with intermittent fasting are unknowingly undoing their caloric deficit by overeating during their eating window.
What you can do: break your fast mindfully, choose unprocessed, nutrient-dense foods that promote satiety, and control your portions.
Reason #3: You’re Not Moving Enough
Regular exercise and non-exercise activity like walking are critical to ensuring that the “calories out” side of the weight loss equation is accounted for. However, when you reduce your calorie intake, your body will respond by reducing your calorie burn or metabolic rate to maintain homeostasis.
What you can do: Keep your physical activity up. Prioritize regular exercise and create opportunities to get more non-exercise activity like walking.
Ki Points on Intermittent Fasting and Weight Loss
That covers what we currently know about intermittent fasting and weight loss.
Here are the Ki Points to remember:
- To lose weight, you must maintain a caloric deficit for a period of time. In other words, you must consume fewer calories than you burn.
- Unlike traditional diets, intermittent fasting doesn’t restrict what you eat. Instead, it promotes weight loss by controlling when you eat.
- In theory, by shortening your feeding window, you will find it easier to consume fewer calories.
- Intermittent fasting’s effectiveness is partly due to its simplicity, which can be adapted to various lifestyles and is relatively easy to sustain.
- Although intermittent fasting can be a powerful weight loss tool for some, it doesn’t work for everyone.
Still wondering if intermittent fasting is right for you? That’s ok. After all, there is no one-size-fits-all approach to weight loss and having discretion before jumping on any bandwagon is always a good idea.
However, if intermittent fasting appeals to you because of its simplicity, and you can visualize it fitting in with your lifestyle, then it might be worth a try.
For tips on how to get started, read this article and let us know how it goes.
Barnosky, Adrienne R et al. “Intermittent fasting vs daily calorie restriction for type 2 diabetes prevention: a review of human findings.” Translational research : the journal of laboratory and clinical medicine vol. 164,4 (2014): 302-11. doi:10.1016/j.trsl.2014.05.013
Tinsley, Grant M, and Paul M La Bounty. “Effects of intermittent fasting on body composition and clinical health markers in humans.” Nutrition reviews vol. 73,10 (2015): 661-74. doi:10.1093/nutrit/nuv041
Ganesan, Kavitha et al. “Intermittent Fasting: The Choice for a Healthier Lifestyle.” Cureus vol. 10,7 e2947. 9 Jul. 2018, doi:10.7759/cureus.2947
Mansell, P I et al. “Enhanced thermogenic response to epinephrine after 48-h starvation in humans.” The American journal of physiology vol. 258,1 Pt 2 (1990): R87-93. doi:10.1152/ajpregu.1990.258.1.R87
Zauner, C et al. “Resting energy expenditure in short-term starvation is increased as a result of an increase in serum norepinephrine.” The American journal of clinical nutrition vol. 71,6 (2000): 1511-5. doi:10.1093/ajcn/71.6.1511
Ho, K Y et al. “Fasting enhances growth hormone secretion and amplifies the complex rhythms of growth hormone secretion in man.” The Journal of clinical investigation vol. 81,4 (1988): 968-75. doi:10.1172/JCI113450
Heilbronn, Leonie K et al. “Alternate-day fasting in nonobese subjects: effects on body weight, body composition, and energy metabolism.” The American journal of clinical nutrition vol. 81,1 (2005): 69-73. doi:10.1093/ajcn/81.1.69
Rynders, Corey A et al. “Effectiveness of Intermittent Fasting and Time-Restricted Feeding Compared to Continuous Energy Restriction for Weight Loss.” Nutrients vol. 11,10 2442. 14 Oct. 2019, doi:10.3390/nu11102442
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