12 Reasons You’re Not Losing Weight While Doing Intermittent Fasting, According To An RD (2023)

There’s nothing more buzzy than intermittent fasting (IF) when it comes to current weight-loss trends. Tons of celebs tout it as their go-to eating approach to get or stay in shape—including Halle Berry, Jenna Jameson, Jennifer Garner, Stassi Schroeder, and Vanessa Hudgens, to name a few.

And the benefits of IF aren’t limited to weight loss. Research (albeit limited!) suggests intermittent fasting may help lower your cholesterol, improve your concentration, and even help you sleep better.

But if you are using IF for weight-loss purposes, know that it's actually pretty easy to do it incorrectly, and stall your weight loss as a result. You kinda have to nail your eating window to reap the health and weight-loss benefits, down to the timing and the foods you eat when you do break your fast.

So if you’ve been trying and trying to lose weight with IF and your body isn’t changing, keep reading for the biggest mistakes people make on IF diets that may impede weight loss, according to registered dietitians—and how to address each issue.

So how does IF work for weight loss, exactly?

“Intermittent fasting is about when you eat,” says Charlotte Martin, MS, RDN, CPT, owner of Shaped by Charlotte, LLC. “Depending on the IF approach, you’re either shortening the eating window each day, or engaging in about 24-hour fasts one or more times a week.” One of the most popular approaches is the 16:8 method, which is when you fast for an 16-hour window, like from 8 p.m. to 12 p.m. the next day.

The Ultimate Guide to Intermittent Fasting

12 Reasons You’re Not Losing Weight While Doing Intermittent Fasting, According To An RD (1)

The Ultimate Guide to Intermittent Fasting

Essentially, by restricting your food intake to a shortened time window, you naturally decrease your caloric intake and, in turn, can lose weight. (Remember, weight loss, at the most basic level, happens when you consume fewer calories than you expend each day.) "Not only are you taking in fewer calories, but you’re also slowing down your insulin pump, which may boost fat burn," explains Martin.

How long does it take to start losing weight when you're doing intermittent fasting?

There are a lot of factors that can contribute to how long it may take for the weight to start coming off. "Rate of weight loss will vary greatly from person to person depending on several factors, including: starting weight, the intermittent fasting approach used, the types of (and how much) food consumed during the eating windows, and more," says Martin.

If you end up reducing your overall caloric intake right away and you consistently eat fewer calories than you expend, then you should start losing weight immediately. "However, you likely won’t notice any weight loss results for at least a couple of weeks," notes Martin, adding that some weight loss in the beginning will "likely be water weight."

“Depending on the calorie amount you consume while intermittent fasting, you could experience an approximate one- to two- pound weight loss per week, which would mean it could take upwards of eight to 10 weeks to notice significant weight loss,” says Kristen Smith, MS, RD, spokesperson for Academy of Nutrition and Dietetics.

If you’re losing more than that? It could be a red flag. “If you notice yourself losing a noticeable amount of weight during the first few weeks of following an intermittent fasting plan, you should likely re-evaluate your calorie intake to ensure you are consuming adequate nutrition to meet your body’s needs,” says Smith.

So if I’m *not* losing weight with IF, what’s the problem?

There could be a few reasons. Here are 12 intermittent fasting mistakes that you might be making, and how to fix them.

1. You’re eating too much during your eating window.

As mentioned, in general, “Weight loss essentially boils down to calories in versus calories out,” reminds Martin. “If you end up consuming the same number of calories (or more) during your eating windows as before you started intermittent fasting, then you won’t lose weight.”

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In other words, if you just pack all of the calories you'd normally eat into your eating window, you're not really changing your diet at all.

How to fix it: Try a calorie-counting app. "Although I don’t typically recommend calorie counting, it may help to track your caloric intake for a few days using a calorie-tracking app," says Martin. "These apps will usually tell you the approximate daily calorie amount you need to be at in order to lose weight. Although these estimations are usually off, they can be used as a good starting point." The app can also reveal meals or specific foods that have more calories than you'd expect, and you can adjust your diet accordingly.

2. You are not consuming enough calories on non-fasting days.

“When you don’t consume an adequate amount of calories on non-fasting days, your body may conserve the energy you consume, rather than burning it,” says Smith.

How to fix it: Make a meal plan for yourself for non-fasting days. “Make a suitable meal plan for non-fasting periods that includes balanced meals consisting of at least 300 to 500 calories per meal.” This way, you take out the guesswork and can ensure that you don't skimp on cals for yourself.

3. You’re eating less-nutritious foods.

"Although the focus of intermittent fasting is on when you eat rather than what you eat, that doesn’t mean you can eat whatever you want during your eating windows and still lose weight," Martin points out. "If your diet consists of mostly calorically dense foods, like fast food, you probably won’t lose weight."

How to fix it: Focus on eating nutrient-dense foods. “Eating foods rich in lean protein, fiber-rich carbs, and healthy fats will help fill you up and naturally reduce your overall caloric intake," she says. Don’t worry: "You can still enjoy some of your less-healthy favorites, like pizza and ice cream, in moderation!” she adds.

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12 Reasons You’re Not Losing Weight While Doing Intermittent Fasting, According To An RD (2)

4. You’re not fasting long enough.

“If you decide on a time-restricted feeding approach and you only shorten your eating window by an hour or so a day, you likely won’t see much, if any, weight loss,” says Martin. You're just not changing enough from your normal eating routine, tbh.

How to fix it: “Most women find success with about a 10-hour eating window, meaning a 14-hour fast," says Martin. "You can always start with a longer eating window and work your way down if your usual eating window is much longer than this,” she suggests.

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5. You’re skipping meals during your eating window.

“Skipping meals and not eating enough during your eating windows can cause you to be extremely hungry during fasting periods, making it more likely that you’ll end up breaking your fasts,” says Martin. “Restricting yourself too much during one eating window can also lead you to bingeing and overeating during your next eating window, which can also increase overall calorie intake.”

How to fix it: "Make sure you’re eating until you're full and satisfied, but not overstuffed, during your eating windows," she says. Martin also suggests doing some meal prep on the weekends for the week ahead to ensure you don't skip meals when you get busy or thrown off your schedule.

6. You chose the wrong type of fasting plan.

"There are several types of intermittent fasting plans. Not all plans may fit your lifestyle or help boost your specific metabolic rate," says Smith. For instance, if you are training for an endurance challenge and picked a plan that prevents you from eating in the morning, when you need fuel for workouts, you may fall off the IF wagon in the process. (and also harm your body and performance).

How to fix it: “Consider choosing an intermittent fasting plan that best matches your lifestyle and can be maintained for the long-haul,” says Smith. You might want to consult a registered dietitian to help you make this decision and assess your lifestyle and dietary needs.

7. You aren’t sleeping enough.

“Few studies have looked at the direct correlation with weight loss and sleep while following an intermittent fasting plan, however in general,several studies have shown a connection between adequate sleep and positive weight loss outcomes,” says Smith.

How to fix it: You've heard it before, but, “Make an effort to sleep at least 7 hours per night,” says Smith. (Tough, but do your best!)

8. You’re working out a ton.

"Oftentimes people will start a new eating regimen, like a fasting diet, at the exact same time they decide to start a new exercise plan or boost the current exercise plan they’re on," says Martin. "Over-exercising or working out too intensively, especially while attempting to reduce food intake, can cause energy levels to drop and hunger levels to skyrocket." As a result, you may end up eating more calories during your eating windows than you’re burning, even with the intense exercise, she notes.

How to fix it: If practicing full-day fasts (like with the 5:2 method, for example), be sure to keep exercise light on fasting days. "In general, make sure your exercise regimen is challenging but still doable and enjoyable. If you notice you feel ravenous on the days you exercise, it may mean you’re pushing yourself too hard," says Martin.

9. You’re not hydrated enough.

Not drinking enough water during your fast may not only leave you dehydrated, but by not drinking enough, you’re also missing out on water's benefits when it comes to quelling hunger.

How to fix it: Drink up! And you can get fancy with your water. Intermittent fasting-approved drinks include: hot tea, black coffee, seltzer water, iced tea, tea or coffee with Stevia.

10. You’re not following your plan as instructed.

“Following an intermittent fasting plan can be difficult for some dieters as they aren’t used to going long periods of time without eating,” says Smith. So if you keep cheating your plan week to week or cutting corners, it probably isn't going to yield the weight-loss benefits you were hoping. So, you may want to reconsider whether IF is right for you and your lifestyle.

How to fix it: “Choose an intermittent fasting plan that best matches your lifestyle and can be followed for longer periods of time,” says Smith.

11. You don’t plan ahead.

“Planning ahead is an important aspect of maintaining any type of healthy intervention,” says Smith.

How to fix it: “Try to plan all your meals and snacks at least a day in advance. Having a plan of what you will prepare, including packing meals and snacks in advance, or scoping out restaurant menus to decide what you will order,” says Smith.

12. You feel guilty because you broke a fast.

IF takes practice and patience. "Most individuals who try IF, regardless of the approach they choose, will end up breaking a fast ahead of schedule at some point or another," says Martin. "If you’re serious about continuing IF, it’s important not to feel guilty, ashamed, or mad at yourself for doing so and to get back to a regularly scheduled program as soon as possible."

How to fix it: It’s important to give yourself some grace and to move on! "Remind yourself that IF takes some trial and error—it’s inevitable that your IF schedule won’t always go according to plan," says Martin.

12 Reasons You’re Not Losing Weight While Doing Intermittent Fasting, According To An RD (3)

Emily Shiffer

Emily Shiffer is a former digital web producer for Men’s Health and Prevention, and is currently a freelancer writer specializing in health, weight loss, and fitness. She is currently based in Pennsylvania and loves all things antiques, cilantro, and American history.

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