Intermittent fasting but not losing weight? 7 reasons why

Key Points

• Not everyone loses weight on intermittent fasting, even if you're following all the rules perfectly
• Your body's unique needs, medications, and lifestyle all affect how well fasting works for weight loss
• Simple changes like choosing nutrient-rich foods, balancing your plate, and managing stress levels can help improve your weight loss results
• If fasting feels too restrictive, there are other proven ways to reach weight loss goals

Feeling stuck with intermittent fasting? You've followed the schedule religiously, yet the numbers on your scale haven't changed. While social media showcases dramatic weight loss transformations from fasting, your journey might look different—and science helps explain why.

Research shows that intermittent fasting can support weight management, but its effectiveness varies significantly between individuals. 

Like any weight loss approach, fasting works through fundamental principles of metabolism and energy balance. Understanding these principles—and common pitfalls—can help you determine whether your fasting strategy needs adjustment.

What is intermittent fasting? How does it affect weight loss?

Intermittent fasting is an eating pattern that cycles between periods of eating and fasting—it’s not about what you eat but when you choose to eat. At its core, this approach works by naturally reducing your overall caloric intake while optimizing your body’s fat-burning potential.

Research demonstrates that intermittent fasting may not only support weight loss but may also offer broader health benefits. It may help lower cholesterol levels, reduce inflammation, and lower the risk of developing conditions like type 2 diabetes.

Intermittent fasting may sound simple—just don’t eat for a while, right? But the reality is that timing isn’t everything. Your body’s response to fasting depends on various factors, from the foods you choose to your overall lifestyle habits.

“While research supports intermittent fasting for short-term weight loss, maintaining the rigid diet can be challenging in the long term,” explains registered dietitian Rita Faycurry, RD. “Focusing on sustainable, consistent eating patterns throughout the day—rather than restricting eating windows—may lead to better long-term weight management for most people."

Understanding intermittent fasting can help set realistic expectations for how long it takes to lose weight, considering factors like starting weight and health habits.

Reasons why you’re not losing weight on intermittent fasting

1. The diet may not be right for you (and that’s alright)

Setting rigid meal times can affect your relationship with food. While some people prefer fasting windows, many others find themselves preoccupied with thoughts of the next meal. This type of constant “food thoughts” can lead to more anxiety and stress around eating.

Plus, battling food cravings for hours can lead to consuming more calories than usual or binge eating when it’s time to eat again. This pattern offsets the benefits of fasting. The cycle of restriction and then overeating or binge eating can be exhausting, interfere with weight loss, and impact your emotional well-being.

For many, this approach may not lead to sustainable weight loss.

 💡Expert tip

"If intermittent fasting feels too restrictive or isn't sustainable for you, that's perfectly okay," says Faycurry, RD. "There are many other approaches to healthy eating that don't involve strict time windows. A registered dietitian can help you find a more balanced eating pattern that fits your lifestyle, fight food cravings, and reach your weight loss goals."

Your calorie intake is higher than you think

Many people assume that restricting their eating window automatically leads to eating less. However, without conscious attention to portion sizes, it may be surprisingly easy to consume too many calories during the shortened time period.

To manage your weight, you will need to eat fewer calories than you burn., One way to do this is to opt for whole, minimally processed foods even during intermittent fasting eating windows.

Also, studies show that food tracking leads to greater weight loss success. Maintaining a detailed food log helps you understand your eating patterns, identify portion sizes accurately, and spot emotional triggers that lead to overeating.

💡Expert tip

"To lose weight, you still need to consume fewer calories than your body uses," explains Faycurry, RD. "The timing of your meals does matter, but calories still count. To start with, you could track your food intake in a journal. It can help you understand how much food you’re eating at a time. These notes can also help you discuss your weight loss plateau with a dietitian.”

Please note: If tracking your food triggers anxiety or concerns about disordered eating, please skip this step. Consider meeting with a registered dietitian who specializes in eating disorders to help you achieve your health goals while helping you avoid triggers.

3. What you eat matters

The types of foods you eat during your eating window matter as much as the timing. Following a healthy diet and avoiding ultraprocessed foods, added sugars, and refined carbohydrates can prevent spikes in your blood sugar levels and reduce the likelihood of your body storing fat—even if you’re following your fasting schedule perfectly.

This metabolic response may cancel out the potential benefits of fasting, regardless of how strict your eating windows are. Choosing the right foods can benefit weight loss by creating a calorie deficit and supporting overall metabolic health.

💡Expert tip

"What you eat is just as crucial as when you eat," explains Faycurry, RD. "The key to lasting success isn't just about meal timing. It's about choosing nutrient-rich whole foods, lean protein, non-starchy vegetables, and healthy fats over packaged and ultraprocessed options. Plus, portions matter. Even the best fasting schedule won't deliver results without focusing on food quality."

4. Add the right physical activity to the mix

While fasting helps create a framework for weight loss, exercise also plays a key role in your success.

Regular physical activity boosts your metabolism, builds muscle mass, and enhances your body’s ability to burn fat. Research suggests that exercising during your fasting window might even amplify these benefits.

💡Expert tip

"Exercise is a great complement to nutrition for overall health,” Faycurry, RD. "Together, the sum is greater than the parts: physical activity and diet help you achieve healthy weight loss. Combine moderate cardio with strength training to help you boost your metabolism and support your weight loss journey.”

5. Your hormones may be affected (particularly if you’re female)

Some studies claim that intermittent fasting may affect women differently than men, especially during their reproductive years. However, these claims may be based on animal studies. More human studies are needed to learn if extended fasting could disrupt estrogen and progesterone levels and affect menstrual cycles.

💡Expert tip

Faycurry, RD, says, "Women may need to approach intermittent fasting for weight loss with extra care. While fasting may help with weight loss, some suggest it may affect hormonal balance and reproductive health. There’s not enough research in humans to know for sure.”

Please note: Always consult your healthcare provider before starting intermittent fasting, especially if you menstruate or have existing hormonal conditions.

6. Lifestyle adjustments may be needed

Chronic stress elevates cortisol levels, which can increase cravings for foods rich in sugars and fats. This can make fat loss more challenging and increase weight gain, particularly belly fat.

Poor sleep can also disrupt hunger hormones by increasing your appetite. Plus, when you’re awake, your body automatically prepares for a higher activity level than when you’re asleep. This may make it harder to stick to your fasting schedule and make mindful food choices, ultimately hindering your weight loss progress.

💡Expert tip

"Managing stress and sleep is essential for weight loss and overall health," says Faycurry, RD. "High cortisol from chronic stress can derail even the best-laid eating plans. Daily stress-relief practices like a 15-minute meditation, gentle yoga, or even listening to your favorite calming music can help.”

Additionally, aim for a consistent bedtime routine for better sleep, and limit screen time and alcohol before bed. Try to target 7-8 hours of quality rest.

7. Underlying health conditions

Sometimes, when we make big changes to our lives, like a new diet or exercise plan, we may blame them for more than they actually impact. For example, you may have started an intermittent fasting plan when you noticed some weight gain. But maybe your diet wasn’t the main source of weight gain in the first place.

Underlying medical conditions like insulin resistance, PCOS, thyroid hormones, or other metabolic imbalances may be the real reason you’re not losing weight. Additionally, newly developed food sensitivities, allergies, or poor gut health may be at play, causing bloating, water retention, and weight gain.

For people in menopause, hormonal changes often lead to an increase in belly fat, making weight loss efforts harder. This can complicate managing weight with intermittent fasting, as hormonal shifts and metabolic changes may affect the expected results.

💡Expert tip

"Medical conditions, and even some medications, can significantly impact your weight loss results," says Faycurry, RD. "If you're struggling to lose weight on intermittent fasting, work with your healthcare provider to learn if there are underlying factors to consider. A registered dietitian can also help you customize your nutrition plan to align with your medical needs and realistic weight loss goals.”

How to break through a weight loss plateau

1. Keep what works; lose the rest

If intermittent fasting hasn't delivered the results you hoped for, you've still gained valuable insights about your eating patterns. Perhaps you've discovered you prefer the simplicity of fewer meals in your busy schedule, or you appreciate how fasting can help regulate blood sugar levels when done correctly.

The key is taking what works—like simplified meal planning, less decision fatigue, and longer breaks between meals—and adapting these elements to fit your lifestyle.

This might mean creating an eating pattern that helps you eat healthy when you’re busy and tired, without the rigid rules of traditional fasting.

2. Consider an alternative eating plan

If intermittent fasting plans don’t align with your lifestyle, you have several proven alternatives for managing your weight and blood sugar levels.

The Mediterranean diet, for example, focuses on whole foods, healthy fats like olive oil, and plenty of fresh vegetables. It also allows you to enjoy regular, balanced meals throughout the day.

Similarly, the heart-healthy DASH diet offers a variety of options and emphasizes whole fruits, vegetables, and lean proteins while helping you maintain steady energy levels.

The Blue Zone diet, inspired by regions known for longevity, offers a simpler approach centered on plant-based foods, beans, and whole grains. It emphasizes eating only until you’re 80% full. This “diet” also promotes a healthier lifestyle, including a focus on community, finding purpose, and living mindfully.

No matter what nutrition plan you prefer, the key is finding a natural and enjoyable plan. And if it’s overwhelming to plan meals on a new diet, consider working with a registered dietitian. They can help you plan your meals based on budget, food preferences, and health goals.

3. Get a personalized nutrition plan

Everyone's body, schedule, and relationship with food is different. So, cookie-cutter diets often fall short. A personalized nutrition plan created by a registered dietitian can help you find what truly works best for you.

A dietitian nutritionist will examine your daily life, what foods you actually enjoy, and learn about challenges like budgets, familial eating patterns, and your history with weight loss. They can also help you deal with food cravings and any nutritional deficiencies you may have.

This way, you get a custom eating plan that feels right for you—no more forcing yourself into rigid meal plans that clash with your life.

Final thoughts

Your journey with intermittent fasting is unique, and what works for others might not work for you. Remember that weight loss isn't just about the number on the scale.

Focus on building sustainable habits, listening to your body's signals, and celebrating non-scale victories along the way. With patience, consistency, and the right support from professionals like dietitians, you can overcome these obstacles and find an approach that works best for you.

Find out if fasting is right for you. Find your personal dietitian, covered by insurance.

Frequently Asked Questions (FAQs)

What are the types of intermittent fasting?

Different intermittent fasting schedules offer varying levels of flexibility and intensity. Here are the most popular approaches:

• 12:12 fasting: The gentlest approach, perfect for beginners. You eat within a 12-hour window (like 8 am to 8 pm) and fast for the remaining 12 hours. While weight loss may be slower, it's often easier to maintain over time since much of the fasting occurs when you’re sleeping.
• 14:10 fasting: A moderate step up from 12:12 with a 14-hour fasting window. For example, if you finish dinner at 8 pm, you'll have your first meal at 10 am the next day.
• 16:8 fasting: The most popular weight loss window is a 16-hour fast with an 8-hour eating window. The idea is that the body may burn more fat faster with a longer fasting window. However, it is also difficult to sustain in the long term.
• 5:2 fasting: This type of fasting is incredibly difficult to sustain and is considered an extreme diet. It recommends eating normally five days a week and then significantly reducing your calorie intake (500 for women, 600 for men) on two non-consecutive days.

“Most dietitians do not recommend the 5:2 type of fasting because it could lead to severe hunger on fasting days, nutritional deficiencies, fatigue, headaches, and the potential to overeat on non-fasting days,” says Faycurry, RD. “It could also lead to an unhealthy relationship with food.”

Can medications affect my weight loss results on fasting?

If you're on prescription medications—especially for blood pressure, heart conditions, or diabetes—fasting might not be your best option. Many of these drugs need to be taken with food or right after meals to be effective.

Fasting makes you skip meals, and if you’re taking insulin, your blood sugar could drop to dangerously low levels (hypoglycemia) without adjustments to your dosage by a healthcare provider.

Additionally, certain antidepressants and antipsychotic drugs like Mirtazapine, Lexapro, Zoloft, and Olanzapine may increase your food cravings and weight gain, making it extra challenging to achieve your weight loss goals and stick to your fasting window.

It’s best to talk to your doctor or a registered dietitian before you begin any type of fasting.

Is it normal to feel hungry during fasting windows?

Some hunger pangs during your fasting hours may be normal, especially when you first start. Your body has gotten used to eating at certain times, so adjusting to your new schedule takes a few weeks. But feeling dizzy, exhausted, or unable to focus isn't normal—these are your body's way of saying something needs to change.

Faycurry, RD notes, “If intense hunger hits during your fasting hours, try adding more filling foods to your meals—like lean proteins and fiber-rich vegetables. Start slowly with fiber to let your stomach adjust. But here's the important part: if you feel unwell after starting your fasting routine, stop fasting immediately and check in with your doctor.”

If you’re still struggling after adjusting your meals, it might be time to reconsider your fasting schedule or explore more balanced approaches to healthy eating.

Not losing weight by fasting? Find out why. Talk to a weight loss dietitian, covered by insurance.

The views expressed by authors and contributors of such content are not endorsed or approved by Fay and are intended for informational purposes only. The content is reviewed by Fay only to confirm educational value and audience interest. You are encouraged to discuss any questions that you may have about your health with a healthcare provider.