Troubleshoot Intermittent Fasting: 12 Reasons Why You’re Not Losing Weight (and how to fix them)

People talk about Intermittent fasting like it’s the holy grail in weight loss. It’s so easy they say. 

Just skip breakfast. Don’t eat after 8pm. Watch that body fat drop!

Well, this is not your experience. If you’re asking yourself “why am I not losing weight on intermittent fasting?” this post is for you. Let’s dive into 12 common reasons why you’re not losing weight with intermittent fasting (and how you can fix them). 

What Intermittent Fasting Is (and Isn’t)

Intermittent fasting (IF) is a time-restricted eating pattern. Not a diet plan. This means you change when you eat (not what you eat) to lose weight.  

IF works by causing a metabolic switch. When you eat, your body breaks down food into glucose (aka sugar). In a fasted state, you use up the glucose and then your body burns fat for energy. So this is what causes weight loss and other health benefits. 

Now, weight loss is (probably) the most popular reason people do IF. But the other benefits are linked to better metabolic health. Research has shown IF helps lower risk for heart diseases, insulin resistance (and type 2 diabetes), obesity, neurodegenerative disorders like Alzheimer’s, and even some cancers. 

But you came here to figure out why you’re not losing weight IF. So…

Why am I Not Losing Weight on Intermittent Fasting?

These are the 12 most common reasons your IF isn’t working:

  1. Your fasting window and eating window are wrong (for you)
  2. Your fasting window is too short. 
  3.  Too many calories during your eating window
  4. Not eating enough
  5. Not enough nutritious foods during your eating window
  6. You need more physical activity 
  7. You’re working out too much
  8. More strength training. Less cardio. 
  9. Sleep–you need more of it. 
  10. You’re not hydrated
  11. You have a health condition that makes it hard to lose weight (no matter what you do)
  12. Intermittent fasting just isn’t for you. 

Your fasting window and eating window are wrong (for you)

The nice thing about IF is that it’s flexible. You can fast whenever you want and eat whenever you want.  But since there are only so many hours in a day, people tend to do IF in similar patterns. 

The 3 most common ways to do IF are:

  • 16:8–You fast for 16 hours, then eat during an 8-hour window. People do this everyday. 
  • 5:2–You eat like normal for 5 days. But for 2 days (not back-to-back), you restrict your intake to 500-600 calories total. 
  • Eat-stop-eat– fast for 24-hours for 2 days week (not back-to-back) 

Other popular methods are:

  • The Alternate-day fasting: You fast every other day. 
  • The Warrior Diet: You eat one big meal a day but snack on small amounts of raw fruit/veg throughout the day. 
  • OMAD diet: Eat one meal a day. It’s usually a big meal because you need to meet your daily intake goals in just one meal. 

It’s important to choose a plan that works for you otherwise you won’t follow it (and get the weight loss you’re looking for). The fasting window needs to be long enough to work, but not so long it’s unbearable. 

People seem to think that the more hardcore you go, the better results you get. That’s not true. 

There is research that supports alternate-day fasting as the most effective for weight loss. But you can get the weight loss and metabolic benefits from any IF eating pattern. Because they do the same thing: put your body into a period of fasting. 

When I first tried IF, I chose the 16:8 schedule. I can’t imagine skipping a whole day of eating (and I don’t want to). 

I did what my friend did– I stopped eating at 8pm and broke my fast at noon. But I was way too hungry before noon to keep up with that schedule. So I had dinner earlier and added a late morning snack in to carry me through until lunch. That worked for me. And it fit into my 16:8 schedule. 

And if 16 hours feels too long, try fasting for 14 hours and eating during a 10 hour window. One study looked at the effects of time-restricted eating on body weight among participants with obesity. They found that after 8 weeks (and participants were also in a weight loss program), participants lost weight and improved their fasting blood glucose levels.

THE FIX: Try a different eating schedule. If you keep forcing a schedule that doesn’t work for you, you’ll likely end up snacking when you’re supposed to be fasting or overeating in your periods of eating. You can also gradually increase the amount of time you fast. Slow and steady wins the race is a cliche for a reason…

Another problem could be that your fasting window isn’t long enough. 

Your fasting window is too short.

Your body needs time to burn through that glucose. So you don’t have enough hours of fasting, your body won’t switch to burning fat. And that’s key to IF. 

The body can enter ketosis after 12 hours of fasting. Which means any late night snacking (or early morning–who am I to assume what you do at 2am) will stop you from entering ketosis because there will be enough glucose for your body to use. 

THE FIX: Make sure you’re fasting at least 12 hours straight. 

Too many calories during the eating window

One of the reasons IF helps with weight loss is because people tend to eat fewer calories. It makes sense when you think about it. 

Some people skip breakfast then eat a normal lunch at noon. The average breakfast cereal is around 250 calories. So if you just skip that morning bowl of cereal, you’re creating a caloric deficit (with helps with weight loss)

Also, you can only eat so much during your eating window. Your lunch and dinner might have a slightly higher number of calories than usual, but most people don’t have drastically bigger portion sizes. 

Now, if you’re coming out of your periods of fasting with a hunger like no other, chances are you want to eat anything you can get your hands on. And you might end up binging. If this happens a lot, you could be eat too many extra calories to see any weight loss. You might even see weight gain. 

Alcohol is another thing that could be adding extra calories without you noticing. 

THE FIX: Track your intake for about a week to get the numbers. Also keep track of how often you break your fast. 

You could be struggling to lose weight if you’re not eating enough calories too. 

Not eating enough during the eating window

Under eating is not your friend in weight loss. People say your calories in should be less than your calories out to create a calorie deficit. But you can only cut so many calories (in a healthy way) before you’re buying a one way ticket to malnutrition. Another thing we ain’t got time for. 

In the short term you might see some weight loss if you’re under eating. But it’s not sustainable weight loss. Plus your body will break down muscle mass if it’s not getting enough calories to support you. 

ACTION: Figure out how many calories you need to maintain your current body weight. Here’s the Mifflin- ST. Jeor equation if you love doing math. 

Men: [10 x weight (kg) + 6.25 x height (cm)] – [5 x age (y) ] +5

Women: [10 x weight (kg) + 6.25 x height (cm)] – [5 x age (y)] – 161

Multiply by activity level (1.2-1.9)

Activity level 

Activity factor 

Sedentary – little to no exercise 

1.2 

Lightly active (1-3 days/week)

1.375

Moderately active (3-5 days/week)

1.550 

Very active (hard exercise 6-7 days/week)

1.725 

Extra active (exercise + physical job)

1.9

OMG Ame why is there math?? Anyone that tells there is no math in nutrition different clearly doesn’t understand that nutrition is part of SCIENCE. Where math happens.

(But you can also use an online calorie calculator). 

Let’s say my maintenance calories are 1800 calories. Now subtract 250-500.

1800-250= 1550kcal

1800-500=1300kcal

That’s roughly want your caloric intake should be for a day. It’s up to you how much you want to cut. I’ve only ever cut my calories by 500 a day when I was trying to lose weight for a boxing match. 1300kcal a day is not fun let me tell you. 

But again it’s up to you how much you want to cut. Don’t cut by more than 500 calories a day though. 

The FIX: Try calorie counting for a week or two to see what your intake looks like. I’ve used myfitnesspal and Cronometer. 

Don’t worry if it doesn’t match what you think it should be. Collect the data first and THEN make changes. And while you’re looking at how many calories you eat, take a look at what foods you’re eating too. 

Not enough nutritious foods during your eating window

There’s this myth that you can eat whatever you while when intermittent fasting. Even though IF is not a diet, your food choices still matter. 

So, the quality of your diet could be one reason you’re not losing weight on IF. 

THE FIX: Aim for a balanced meal where you have your 3 macronutrients (carbs, protein and fats). And enough variety to get your micronutrients in. It’s helps if you know how to read a food label so you know what’s in your meals. 

Take a look at the DASH diet, Mediterranean diet, pescatarian diet or plant-based diets if you need ideas on what to eat. These diets will definitely help if you don’t have enough protein or fiber in your diet (which can make it hard for you to lose weight on IF). 

Not enough protein and fiber in your diet

Protein, we love it. Because protein preserves your muscle mass (which helps give you that toned look) and supports tons of bodily and cellular processes. It also helps you feel full for longer. Without enough protein, you might eat more than you planned. Or more often because you’re feeling hungry. 

Fiber is also important in weight loss. It takes longer for your body to digest fiber so you feel fuller for longer. This helps with controlling your appetite. 

THE FIX: Make sure you have enough lean protein (fish, chicken, lean cuts of meats, and plant-based proteins) and soluble fiber in your day of eating. You want enough protein to fit the size of your palm, and it’s hard to go wrong with half a plate-full of vegetables. 

Food and food habits aren’t the only things that affect your weight loss. 

Experiencing sleep deprivation

Sleep deprivation can have a significant impact on your weight loss goals when practicing intermittent fasting. When you don’t get enough sleep, it can disrupt your body’s natural processes, including metabolism and hormone regulation.

This can lead to increased cravings for unhealthy foods and decreased willpower to make healthy choices during your eating window. Additionally, lack of sleep can contribute to higher stress levels, which can further hinder weight loss progress.

Prioritizing adequate sleep is essential for optimizing the benefits of intermittent fasting and achieving successful weight loss results.

In order to achieve optimal results with intermittent fasting, it’s crucial to address any issues related to sleep deprivation. Making sleep a priority by establishing a consistent bedtime routine and creating a restful environment are important steps in ensuring quality sleep.

You’re not Hydrated

Water is the elixir of life. When you’re not hydrated enough, your body will tell you. But if you reach for drinks with calories in them like juices, teas/coffees with milk and sugar, or sodas, those calories count. 

Also, sometimes you get hunger instead of thirst signals, and you snack or eat more at a meal. This also increases your total calories for the day and might be why you’re not losing weight. 

The FIX: Drink enough water.

How much is enough water per day?

8 glasses a day is a common answer when people ask how much water to drink. Ultimately it depends on your level of activity, your weight, and your age. 

In my nutrition classes, we calculated fluid needs using body weight in kilos and age. This was for like hospital patients, but the math still works. 

To get your body weight in kilos, take your weight (in pounds) and divide by 2.2. For example, my weight is 132lbs/2.2 = 60kg. I’m 60kg. 

Then if you’re under 55, 35ml per kilo is the recommended amount of fluid. I’m 32 so I would use 35 mL. 

60kg x 35ml = 2100ml. If you live in the US, you want to get this into ounces. After living abroad for 10 years, I love mililiters. I love the metric system. But, here I am again. In the US.

And in the US, there are about 29.6 ml in one ounce. So let’s do more math (yay). 

2100ml/29.6ml = 71 ounces in a day. I need roughly 9 cups of fluids per day. If I’m very active in a day, like I’m hiking all day in the sun, I’ll drink more. But this gives me a guide on how much my body needs.  

Additionally, dehydration can slow down your metabolism and make it harder for your body to burn calories efficiently. To stay well-hydrated during intermittent fasting, be sure to drink enough water throughout the day.

More strength training. Less cardio. 

You can do cardio until you’re blue in the face (please don’t)…and not lose any fat.

Cardio is great for weight loss. As in a number.

But when people say they want to lose weight, they mean lose fat. Because if your body weight is 140lbs but you’ve toned AF, I’m gonna guess you don’t care about dropping weight (unless you need to cut weight for something like boxing, wrestling or a bodybuilding competition). 

Resistance training helps with fat loss. Plus it helps reduce your risk for osteoporosis. Ain’t nobody got time for osteoporosis when we’re old. So if you’re not strength training at least 2 times a week, start there. 

If you’re already at 2x a week, try going up to 4 days. Give it some time because you’re building muscle. But take a picture of you now and then another one after 2-3 months of strength training. I bet you’ll notice a difference. 

You have a health condition that makes it super hard to lose weight (no matter what you do). 

People assume that if we have a lot of body fat, it’s because we need to eat better and exercise more. These same people (probably) never heard of PCOS, PCOD, depression or cushing’s syndrome. 

It’s not just diet and lifestyle– our genes and mental healthy play a role too in fat/weight loss. 

Now. Do we live in a society that still thinks thin = healthy? Yes. And that sucks. What sucks more is people do judge you based on how you look. I hope that changes some day. But I also want to be real with you and acknowledge that I know that happens. 

I don’t have any of these conditions, so take this with a grain of salt– Focus on what you can control. Focus on building those healthy habits for better health, not just weight loss. 

Intermittent Fasting might not be right for you (and that’s ok)

Studies show the benefits of intermittent fasting. But you can get the same results from calorie-restricted diets and an active lifestyle. So if IF isn’t working out for you, that’s ok. it’s not the only way. 

Takeaway

The bottom line is that there’s are many reasons why you might not lose weight on intermittent fasting. This list is a good place to start thinking about your food and lifestyle habits though. And figure out what is or isn’t working. 

You might also want to work with a registered dietitian who can help you figure out the best way to reach your weight loss goals (and support you along the way).