Even though we hear all these weight-loss success stories from people who have tried intermittent fasting, you may have gained weight. So now you’re probably understandably upset and wondering, “Why am I not losing weight on 16:8 fasting”? 

You may be putting on weight while fasting for two reasons.

Table Of Contents

1. You’re Eating Too Much!

Do you gain weight before you lose it? Extending your fasting window is problematic and causes people to feel starving. That said, when you break your fast, you may be eating very calorically dense meals that cause you to be in a caloric surplus day after day. 

Try logging your food and determining approximately how many calories you are consuming and compare that to how many calories you need to ensure you are not overeating.

Another strategy is to prepare a meal to break your fast. This way, you are more likely to have some control over the dinner when you are the hungriest and, therefore, have control over your caloric intake.

Lastly, make sure you are eating enough protein and fiber. Both help keeps you full and can affect your hunger throughout the day.

2. I Keep Gaining Weight Even Though I Don’t Eat Much – You Aren’t Eating Enough!  

While this might seem counterintuitive, you can actually gain weight when you don’t eat enough. This means that some individuals will gain weight while fasting. This is because your body can sense when you are in a caloric deficit and will make physiological changes that decrease your caloric output (how many calories you burn daily). 

This means that your overall metabolism slows down

To determine if this is what you are doing, try logging your food and comparing that against the calories you need. If you are in a deficit daily, especially in extreme debt, try increasing your calories. This may mean you have to decrease your fasting window to do this. 

Some individuals will experience intermittent fasting weight gain, likely due to them not eating enough, their metabolism decreasing, and then eating the way they did before they started fasting. This puts them in an extreme caloric surplus and will contribute to weight gain. 

Intermittent fasting can be helpful, too, but if it isn’t working for you, you may need to stop.

Can Intermittent Fasting Cause Weight Gain?

You may be aware that fasting is a dietary practice that involves alternating between periods of eating and fasting. This method of eating has become very popular recently due to its potential benefits in promoting weight loss and improving metabolic health.

That being said, you’ve brought up an interesting point. Can intermittent fasting cause weight gain? 

The short answer: it can, but only sometimes, and it depends on various factors. Let’s explore this a bit further.

Calorie Intake During Eating Windows

Firstly, one of the reasons why intermittent fasting might lead to weight gain has to do with what and how much you eat during your “feeding” window. Some people, thinking that they’ve “earned” the ability to eat freely during their eating window, might consume more calories than they would under normal circumstances. Overeating, even within an intermittent fasting schedule, can lead to weight gain.

Quality of Food

Secondly, the quality of food matters. You must consume nutrients if your eating window is filled with high-calorie, processed foods. Over time, weight gain may result from this. Nutrient-dense foods help keep you feeling satiated, which can help manage your overall caloric intake.

Changes in Metabolism

Some research also suggests intermittent fasting leads to metabolic adaptations promoting weight gain. While these effects are relatively minor and temporary, they could contribute to weight gain if combined with overeating or poor food choices.

Exercise and Physical Activity

If a person significantly reduces their activity level while doing intermittent fasting (perhaps due to feeling tired or weak during fasting periods), this could lead to weight gain. Maintaining a balanced approach to exercise while fasting intermittent fasting is necessary.

So weight gain largely depends on how you implement this dietary strategy and how it interacts with the rest of your lifestyle.

Gaining Weight on 16:8 Intermittent Fasting: 3 Common Purposes 

​​A popular approach to fasting is the 16/8 intermittent plan, where individuals eat for 8 hours – then fast for the remaining 16 h. It has been lauded for its potential benefits in weight management and metabolic health. 

There’re indeed scenarios where it could lead to weight gain. Here are three common reasons:

1. Overeating during the feeding window: One of the principal reasons individuals might gain weight during 16:8 intermittent fasting is overeating during the feeding window. Some people may believe they can eat as much as they want in the 8-hour window, and if you devour more calories than your body requires, you can still put on weight. 

2. Eating poor-quality foods: The quality of your food plays a significant role in your overall health and weight management. If most of your intake during the eating window comes from processed, high-sugar, high-fat foods, it could lead to weight gain.

3. Reduced physical activity: Some people may experience fatigue or reduced energy levels during fasting hours, resulting in decreased physical activity. Moving less and burning fewer calories could contribute to weight gain, even if your dietary habits have changed. To counteract this, try scheduling workouts during your eating window when you’ll have more energy.

2 Weeks of Intermittent Fasting No Weight Loss? – Reasons Why Your Fasting Plan May Not Be Working 

You’re not alone in wondering about this – many people expect to see results relatively quickly when they adopt a new dietary strategy, such as intermittent fasting. If you’ve been practicing intermittent fasting for two weeks and haven’t seen any weight loss, there could be several reasons for this. 

As we already mentioned, the food you eat during your eating windows matters as much, if not more, when you eat. Foods high in added sugars, unhealthy fats, and empty calories can stall weight loss, even if you’re practicing intermittent fasting.

  • 2 weeks is a relatively short amount of time for weight loss. Aiming for a weight loss rate of about 1-2 pounds per week is recommended for sustainable, healthy weight loss

This means you might wait to see the main scale changes.

Certain medical conditions, like hypothyroidism or PCOS, can affect your metabolism and make it more problematic to lose weight. It might be worth speaking to a healthcare provider if you’re struggling with weight loss despite your best efforts.

Also, read – How to Lose Weight With PCOS

Understanding Intermittent Fasting Water Retention 

Before diving into intermittent fasting, let’s briefly touch on what water retention means. 

Water retention, or edema, occurs when excess fluids build up inside the body. This can lead to feelings of bloating or puffiness and changes on the scale.

When you start an intermittent fasting regimen, you may initially see a rapid drop in weight. This is often primarily due to loss of water weight rather than fat loss. Here’s why: When you fast, your body turns to glycogen (stored carbohydrates) for energy. As glycogen is used, your body releases the water it holds onto to store these carbohydrates.

However, once you break your fast and begin eating again, your body replenishes these glycogen stores and the associated water. This can sometimes result in what appears to be a quick weight gain, but it’s essential to understand that this is mainly water weight, not fat.

Changes in hormones such as cortisol, the stress hormone, can also affect water retention. If intermittent fasting is causing you significant stress, this may increase cortisol levels, leading to water retention.

Lastly, remember that the numbers on the scale don’t always reflect fat loss or gain. Fluctuations due to water weight are entirely normal and to be expected, especially with dietary strategies like intermittent fasting. 

Also, read – Psychology of Eating: How Food Affects Mood

What to Do When You’re Not Losing Weight Intermittent Fasting 20/4 – Troubleshooting Tips

The 20/4 fasting schedule, often referred to as the Warrior Diet, is quite rigorous, and not seeing the results you expected can be disheartening. 

But don’t worry! There’re several troubleshooting strategies we can explore to help get your progress back on track.

  • Examine Your Caloric Intake: Weight loss ultimately leads to a calorie deficit. You won’t see weight loss if you eat more calories than you burn, even within your 4-hour eating window.
  • Check Your Food Quality: Prioritize nutrient-dense foods like fruits, vegetables, lean proteins, and whole grains. Avoid foods high in added sugars and unhealthy fats.
  • Ensure Adequate Sleep: Poor sleep can disrupt your body’s hunger hormones and potentially lead to overeating. Make sure you’re getting enough quality sleep.
  • Keep Active: Regular physical activity can help create a calorie deficit and benefit health. It’s advisable to include some physical activity in your daily schedule.
  • Limit Processed Foods: Even within your eating window, consuming too many processed foods can hinder your weight loss efforts. They often contain hidden sugars and unhealthy fats.
  • Mind Your Eating Speed: Eating too quickly can lead to overeating before your body recognizes it’s complete. It’s good to take your time and savor your meals.
  • Track Your Intake: Keeping a food diary can help identify potential issues and give you a clearer picture of your calorie and nutrient intake.
  • Reduce Stress: High-stress levels can lead to overeating or poor food choices. Consider incorporating stress-management techniques like yoga, meditation, or deep breathing.
  • Don’t Over-Restrict: Overly restricting your food intake during your eating window can lead to overeating later and slow your metabolism. Ensure that you consume sufficient food to provide energy for your body.
  • Watch Your Alcohol Intake: Alcohol can contribute a significant amount of empty calories and stimulate appetite, leading to overeating.
  • Consider Other Health Factors: If you’re struggling with weight loss, other underlying health issues, such as hormonal imbalances or metabolic conditions, could be at play. 

How to Keep Weight off After Fasting: Nutritional Supplements Might Help You 

Adding certain nutritional supplements to your routine can help, but remember, they should be used as a part of a well-rounded, healthy lifestyle, not as a stand-in for a balanced diet or regular physical activity. 

Let’s explore some supplements that could assist you:

Protein Supplements

Protein is essential for preserving muscle mass, especially during weight loss. Including a protein supplement, like a whey protein shake, could help meet your protein needs, keep you satiated, and reduce the likelihood of weight regain.

Fiber Supplements

Dietary fiber can help keep you feeling total, deter overeating and help with weight maintenance. Psyllium husk or inulin are joint fiber supplements.

Omega-3 Fatty Acids

Omega-3s, found in fish oil supplements, can support overall health and help regulate appetite and body weight, though more research is needed.


Probiotics, particularly Lactobacillus and Bifidobacterium groups strains, may help regulate body weight and fat mass. However, their effects seem modest, and more research is required.

Vitamin D and Calcium

Some research suggests that these nutrients when taken together, help maintain weight loss by decreasing appetite or fat storage.

Green Tea Extract

Green tea extract is high in catechins, particularly EGCG, which may help enhance metabolism and fat burning. It may help with weight maintenance, although more research is needed.

Keep up the excellent work, and remember: maintaining a weight loss is a long-term devotion, not a momentary fix!

Final Thoughts

All in all, fasting can be a wonderful way to jumpstart a more nutritious lifestyle and even bring about weight loss. However, it’s influential to be aware of the common pitfalls contributing to gaining weight while fasting, such as overeating on your scheduled eating windows or not getting enough physical activity. Paying attention to your hunger and energy levels, finding healthy food choices that fit your schedule, and ensuring you’re getting good physical activity are vital components of intermittent fasting success. 

It’s best to confer with a medical professional when making notable dietary changes and tracking progress. 

These methods will help you take advantage of this diet’s many benefits while avoiding potential pitfalls. With a bit of dedication and decisiveness, you may experience balanced and sustainable success with intermittent fasting.

Asked by: Olga J.

Clinical Project Manager and Writer

With a Ph.D. in nutritional biology, Dr. Richardson is an expert in the field of nutrition, particularly intermittent fasting. Her dissertation project was an intermittent fasting study in athletes, which is where she gained substantial knowledge on the topic. She has contributed to a number of peer-reviewed articles spanning a wide array of topics and works as a freelance writer trying to make scientific knowledge accessible to the public.

Intermittent fasting 101Intermittent fasting mistakes