A lot of people abstain from food for the purpose of losing weight. If you’ve heard about intermittent fasting for weight loss, it’s a popular eating pattern where you fast for a certain number of hours or days in a week depending on what you can tolerate.
This article discusses how intermittent fasting works, how much weight can be lost in a week or month, tips to succeed on this plan, and some drawbacks to be aware of.
Intermittent fasting (IF) is a dietary pattern where you alternate between periods of food restriction and eating. Unlike forgetting to eat your meals, intermittent fasting is purposeful. People do it to intentionally restrict calories and put their bodies in a fat-burning mode.
Aside from weight loss, intermittent fasting has many therapeutic benefits, including decreased blood sugar levels, blood pressure, and triglycerides (*). There are different IF timing schedules that you can take advantage of, which we’ll be getting into in a while.
Here’s how intermittent fasting for weight loss works: By limiting the number of hours you eat, intermittent fasting naturally puts you in a calorie deficit. One of the ways to lose weight is to eat fewer calories than you burn.
If you’ve ever tracked calories in the past — and you should know that calories aren’t everything, especially when it comes to long-term weight loss — you understand that it takes effort and can increase psychological stress (*).
What’s great about intermittent fasting is that it reduces your calorie intake for the day without you needing to count anything. This makes it a better alternative to calorie-restricted diets.
Another way intermittent fasting works for weight loss is by depleting glycogen (the stored form of glucose) in your liver cells. When glycogen gets depleted, your body metabolizes fat for energy (*). This is why, if you’re already on the keto diet, incorporating a fast will help you maintain ketosis or reach it faster if you’ve had a carb-up day.
Intermittent fasting may also help you lose weight by suppressing your appetite. In one study, researchers found that participants who fasted for 18 hours a day had lower levels of ghrelin, the hunger hormone (*).
During a fast, your body usually enters a fat-burning state after 16-18 hours, which falls under the second stage of fasting.
As a powerful weight loss tool, fasting can be used to lose a few pounds in a month. When combined with a very low-carb diet and exercise, weight loss may even be greater within the same period.
How much weight can you lose in a week with intermittent fasting?
According to a review of human findings, intermittent fasting produces a 0.25 kg or 0.55 pounds of weight loss in a week (*).
This is considered a safe rate to lose weight. (Experts recommend losing 1-2 pounds per week and that going beyond this range is considered rapid weight loss.)
How much weight can you lose in a month with intermittent fasting?
Based on the review mentioned above, you can lose up to 1 kg or 2.2 pounds in a month. While this is considered a safe and healthy weight loss rate, note that you’ll be able to lose more when done together with a keto diet.
Ready to start fasting? You can choose from a variety of intermittent fasting methods. However, keep in mind that the best intermittent fasting for weight loss is the one you feel most comfortable with. Consider your schedule and level of experience.
Check out these popular fasting options:
- 16/8 fasting: This requires you to consume food within an 8-hour period and fast for the remaining 16 hours.
- Alternate-day fasting (ADF): You fast for one entire day and then eat the next day. For example, don’t eat anything on Monday, Wednesday, and Friday, and resume your meals on Tuesday, Thursday, and Saturday.
- One meal a day (OMAD): This advanced method involves fasting for 23 hours and eating your meal within a 1-hour window.
- The 5:2 diet: You eat normally for 5 days a week, while you restrict calories to 500-600 for the remaining 2 days. If you dislike the idea of calorie tracking, this approach may not be best for you.
Let’s discuss how to do intermittent fasting in a way that helps you get the best possible results. Follow these tips:
Get fat-adapted on keto.
Being fat-adapted, meaning that your body has successfully adjusted to burning fat for fuel, makes it easier for you to undergo a fast. In contrast, people who aren’t fat-adapted tend to experience intense cravings and tiredness while fasting.
To reach a fat-adapted state, limit your carbs to 50 grams a day and increase your dietary fat. Incorporating regular exercise will also help. You can expect to achieve this state in as little as four weeks after you’ve entered ketosis.
The idea is to avoid pairing up keto and intermittent fasting if you’ve never done either of them before. Start with the keto diet, then add fasting — or the other way around.
Try working out in a fasted state.
Yes, you can exercise during intermittent fasting. A study suggests that endurance training in a fasting state increases lipolysis or the process of fat breakdown (*). This results in increased weight loss.
If you wish to resume your usual exercise routine while intermittent fasting, you may want to stick to low-intensity workouts. Jogging, cycling, pilates, or cutting down on your sets and reps (if you lift weights) will help in decreasing your body fat further while allowing you to survive a fast.
Stay hydrated but avoid drinks that contain calories.
Properly hydrating yourself is one of the keys for a successful fast. This is especially true for those who exercise regularly and during warm and humid weather. Dehydration negatively affects your physical and mental performance (*).
Aside from water, other drinks that won’t break a fast include plain coffee, tea, and one teaspoon of apple cider vinegar mixed in water. In general, beverages that don’t contain any calories are fast-friendly.
Avoid overeating after fasting.
Overeating as soon as the fasting period ends is something that happens to a lot of people. Unfortunately, this can result in consuming too many calories and macronutrients in one sitting.
Carbohydrate-loaded meals will spike your blood sugar and insulin levels. On the other hand, too much protein and fat may cause some individuals to feel uncomfortably stuffed and experience diarrhea.
To avoid overeating, prepare your meal in advance so that when you enter your eating window, you won’t end up binging on whatever you find. Healthy foods to break a fast include bone broth, eggs, fish, avocados, and fermented foods.
Here are the most common mistakes that will prevent you from enjoying and reaping the benefits of intermittent fasting:
- Doing a longer fast right away (for example, OMAD) when you’ve never tried fasting before.
- Not eating enough during your eating window.
- Breaking your fast with unhealthy foods, such as white rice, pizza, desserts, and other foods containing refined carbs and sugar.
- Skimping on sleep, which increases your risk of gaining weight (*).
- Being impatient with weight loss. This causes some people to revert to unhealthy habits.
Intermittent fasting has positive effects, but like any eating plan, there are potential downsides if you’re not prepared or you do it incorrectly.
For example, someone who’s just getting started will likely feel fatigued, irritable, very hungry, and experience diarrhea — these symptoms are similar to the keto flu. Another drawback is the risk of nutrient deficiencies if you often fast for long periods and don’t eat enough within your eating window.
Although fasting promotes weight loss and health, don’t ignore a nutrient-dense diet and consider easing into a fast. Additionally, consult your doctor if you have a medical condition, are pregnant, or breastfeeding.
Here are common questions and answers on intermittent fasting and weight loss:
Is intermittent fasting good for losing belly fat?
Yes. Regardless of your approach — whether you do a 16:8 fast or ADF, fasting in and of itself will decrease your body fat. Combining fasting with other practices like exercise and a low-carb diet helps to increase your results.
Is it OK to intermittent fast everyday?
Some people are drawn to the idea of fasting daily to increase weight loss. It’s possible to do it. However, you need to be aware about potential risks, such as micronutrient losses and possibly a slowed metabolism. Consult a healthcare provider if you need more advice on how often to fast.
Does intermittent fasting work without exercise?
Yes, you can fast without exercising and still see improvements with weight loss — although keep in mind that exercise is extremely helpful for maintaining a healthy weight, among other benefits.
Overall, intermittent fasting is an effective tool for losing body fat on top of improving your health. It can be an alternative to weight loss plans that require calorie counting.
So, should you try it? Definitely, but remember to follow a healthy diet while you’re not fasting and avoid breaking your fast with high-carb and high-sugar foods. Last but not least, find an intermittent fasting method that you’re happy with and can stick to.
Yuan X et al. 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. 2022 March 24