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Should You Try Intermittent Fasting for Weight Loss?

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The Potential of Intermittent Fasting for Weight Loss: Is It Right for You?

Intermittent fasting (IF) has gained popularity in recent years as a weight loss technique. It involves restricting food intake for a certain period, followed by a designated eating period. Some people opt for a "16/8" schedule, which means fasting for 16 hours and eating within an 8-hour window. Others choose a 24-hour fast once or twice a week. While IF can be effective for weight loss, it's not suitable for everyone. It's essential to understand the benefits and potential dangers of IF before integrating it into your life. In this article, we will delve into the science behind IF, its various methods, possible side effects, and the people it's best suited for. Ultimately, we will help you determine whether intermittent fasting is the right approach for you to achieve your weight loss goals.

What is Intermittent Fasting?

Intermittent fasting is not a new concept. It dates back to prehistoric times when our ancestors would go through feast or famine periods. However, in recent years, it has become an increasingly popular approach to weight loss and overall health. Intermittent fasting involves alternating between periods of fasting and eating.

Explanation of the Various Types of Intermittent Fasting

There are several different approaches to intermittent fasting, and the most common ones include:

  • 16/8 Method: This method involves fasting for 16 hours a day and eating within an 8-hour window. For example, eating between 12 PM and 8 PM and fasting from 8 PM to 12 PM the following day.
  • 5:2 Diet: This method involves consuming approximately 500-600 calories two non-consecutive days a week and following a regular diet for the other five days.
  • Alternate-Day Fasting: This method involves alternating between fasting and regular eating days. On fasting days, calorie intake is restricted to 500-600 calories.
  • Whole-Day Fasting: This method involves fasting for a full 24-hours, once or twice a week.

Benefits of Intermittent Fasting

Intermittent fasting has gained recognition, mainly due to its potential weight loss benefits; however, the benefits of intermittent fasting go beyond just that.

  • Weight Loss: Intermitting fasting leads to calorie restriction, which can result in weight loss.
  • Improved Metabolism: It has been suggested that intermittent fasting can improve hormonal levels, reduce inflammation, and improve cellular repair, which contributes to an overall improved metabolism.
  • Reduced Risk of Chronic Diseases: Studies have indicated that intermittent fasting could potentially reduce the risk of chronic diseases such as heart disease, type 2 diabetes, cancer, Alzheimer’s disease, etc.
  • Improved Brain Function: According to studies, intermittent fasting can potentially increase the growth of new nerve cells, which can contribute to improved brain function.
  • Increased Longevity: Studies have indicated that intermittent fasting could potentially increase longevity by improving metabolic health.

Risks and Potential Dangers of Intermittent Fasting

Despite the potential benefits, intermittent fasting does come with risks and potential dangers.

  • Difficulties with Adherence: Intermittent fasting can be difficult to adhere to consistently due to the hunger and changes in eating patterns it can cause.
  • Increased Hunger: Fasting can trigger the release of hunger hormones, which can contribute to cravings and overeating during eating windows.
  • Dehydration: During the fasting period, water intake may be low, increasing the risk of dehydration.
  • Low blood sugar: Intermittent fasting could cause significant fluctuations in blood sugar levels, leading to dizziness, fatigue, and headaches.
  • Overindulgence during the feeding period: It's easy to undo the calorie deficit and weight loss following a fast by overindulging during the eating window.

It's essential to note that intermittent fasting is not recommended for everyone. It's important to consult a healthcare provider before adopting an intermittent fasting regimen, especially if there are any pre-existing medical conditions.

How does Intermittent Fasting Promote Weight Loss?

Intermittent fasting promotes weight loss through several physiological mechanisms. Here's how:

Physiologic Explanation

When we fast, our body turns to stored sugar (glycogen) for energy. Once the stored sugar gets depleted, the body begins using fat as fuel. This process induces ketosis, resulting in the production of ketones, which can lead to weight loss. Additionally, intermittent fasting can reduce insulin levels, promote greater satiety, and improve metabolic rate, leading to fewer calories consumed and burned over time.

Scientific Evidence Supporting IF for Weight Loss

Studies have shown that intermittent fasting can promote weight loss by up to 8% over 3-24 weeks, with a significant reduction in body fat. The following are a few examples of scientific research supporting the effectiveness of intermittent fasting for weight loss:

  • A 2014 systematic review found that intermittent fasting induced superior weight loss than other diets. The review included 12 studies, involving 565 participants.
  • A randomized controlled study in 2016 with 60 obese people found that intermittent fasting led to a significant weight loss of 8.2 pounds compared to traditional calorie-controlled diets, which only led to a 5.7-pound loss.
  • A 2020 study with 84 patients showed that an intermittent fasting approach, specifically the 16/8 method, resulted in a significant reduction of body weight, body fat, and waist circumference, compared to a control group that did not fast.

Comparison to Other Diets and Weight Loss Methods

Intermittent fasting has been compared to traditional calorie restriction and other diets, such as the keto and low-carb diets commonly adopted by those looking to lose weight. Some advantages of intermittent fasting include:

  • Reduced Hunger: Intermittent fasting leads to hunger fluctuations and hormonal changes that trigger greater satiety, which reduces feelings of hunger and hankering for food.
  • Ease of Adherence: Intermittent fasting is easier to follow than many other diets, which require constant calorie counting and portion control.
  • Less Muscle Loss: Unlike traditional calorie restriction and low-carb diets, to name a few, intermittent fasting results in less muscle loss.
  • Extended Metabolic Benefits: Intermittent fasting enhances metabolic health by improving insulin sensitivity, inflammation, and other metabolic markers. Additionally, it has been linked to an extended lifespan in some animal studies.

In summary, intermittent fasting is a promising weight loss strategy backed by scientific evidence. However, intermittent fasting is not right for everyone, and people with some medical conditions should check with their healthcare providers before trying it. Nonetheless, intermittent fasting is worth considering for individuals seeking significant, sustainable, and healthy weight loss.

Possible Side Effects of Intermittent Fasting

When starting intermittent fasting, it's common to experience certain side effects due to metabolic and hormonal changes that occur during fasting periods. However, these side effects usually lessen over time as the body adapts to the new eating schedule.


Headache is a common symptom experienced by people practicing intermittent fasting. It's primarily caused by temporary hormonal changes, dehydration, and caffeine withdrawal. Here are some tips to alleviate headache symptoms during the fasting period:

  • Stay hydrated by drinking plenty of water and electrolyte-rich fluids like coconut water or bone broth.
  • Reduce caffeine intake gradually before starting intermittent fasting to minimize withdrawal symptoms.
  • Do gentle stretches or yoga to relieve muscle tension that may contribute to a headache.

Low Blood Sugar

Intermittent fasting can also cause low blood sugar or hypoglycemia, particularly among those with diabetes or hypoglycemia history. Here are things to do if you experience low blood sugar symptoms:

  • Drink unsweetened fruit juice or eat glucose tablets to raise your blood sugar level.
  • Avoid consuming too much sugar or carbohydrate-rich foods that can cause a rapid increase in blood sugar followed by a crash.
  • Consult your physician to adjust your medications and fasting protocol accordingly.


Dehydration is a common side effect of intermittent fasting, particularly during extended fasting periods. Here are some tips to keep you hydrated while fasting:

  • Stay hydrated by drinking plenty of water and electrolyte-rich fluids like coconut water or bone broth.
  • Reduce excessive caffeine and alcohol intake that can cause dehydration symptoms.
  • Avoid engaging in strenuous physical activity especially in hot or humid environments during the fasting period.


Lightheadedness or dizziness after starting intermittent fasting is often due to a drop in blood pressure. To reduce the likelihood of lightheadedness during fasting, follow these tips:

  • Sit or lie down until the lightheadedness subsides.
  • Drink fluids rich in electrolytes, such as bone broth.
  • Avoid standing up suddenly from a lying or sitting position

Gastrointestinal Distress

Intermittent fasting can also lead to gastrointestinal distress, such as constipation, bloating, and acid reflux. To prevent these symptoms, you can:

  • Ensure you are consuming enough fiber-rich foods during your eating window.
  • Avoid overeating during non-fasting periods, which can cause bloating and acid reflux.
  • Avoid consuming spicy or fatty foods, which can aggravate digestive symptoms.

Intermittent fasting can have incredible benefits for weight loss, metabolism, and overall health, but these positive outcomes have to be weighed against the possible side effects of intermittent fasting. Be mindful of your body's signals and make adjustments to your fasting routine as necessary if discomfort arises. If you have any underlying health conditions, it's best to consult a healthcare provider before commencing an intermittent fasting regimen.

Who Should Consider Intermittent Fasting

Intermittent fasting can be a useful tool for weight loss and improving overall health. However, it's not suitable for everybody. Here are some factors to consider when deciding if intermittent fasting is right for you.

Suitability for Individuals with Lifestyle Constraints

Intermittent fasting can be a great option for those with busy schedules, as it simplifies meal planning and saves time. The flexibility of the schedule means it can be adjusted to fit individual needs. However, people who work night shifts may find it difficult to stick to a regular fasting routine because of their irregular eating and sleeping patterns.

Contraindications for Individuals with Specific Medical Conditions

Intermittent fasting may be contraindicated for individuals with certain medical conditions, such as diabetes, poor kidney function, a history of eating disorders, and pregnancy. People with diabetes need to be aware of their blood sugar levels and adjust their medication accordingly during periods of fasting. Those with poor kidney function should avoid high-protein diets, as they can strain the kidneys. Pregnant women should not fast, as they require adequate nutrition for fetal development.

Age-Specific Considerations

Older adults may need to adjust their fasting periods to accommodate their nutritional needs, as their nutrient absorption tends to decrease with age. Adolescents and teenagers need enough calories to support their physical growth and development, so intermittent fasting is not recommended. Children with certain medical conditions or poor growth also need a consistent and nutritious diet, so parental guidance is essential.

Intermittent fasting is not a one-size-fits-all solution. Before starting an intermittent fasting regime, it's essential to consider your lifestyle, medical condition, and nutritional needs. Consult with a medical professional to determine if intermittent fasting is appropriate and safe for you.

Tips and Strategies for Effective Intermittent Fasting

Intermittent fasting (IF) can be an effective approach to weight loss, but it's essential to implement it correctly to achieve the desired results while minimizing the risk of adverse effects. Here are some tips and strategies to make the most of your IF experience.

Choose an Appropriate Fasting Schedule

There are several fasting schedules to choose from, such as alternate-day fasting, time-restricted feeding, and whole-day fasting. The key is to find a plan that suits your lifestyle, preferences, and nutritional needs. For example, time-restricted feeding may be an excellent option for those who prefer daily fasting intervals, while whole-day fasting may be better for those who can tolerate more extended periods of fasting.

Adjust the Fasting Routine According to the Individual's Needs

Intermittent fasting is flexible and can be adapted to various lifestyles and goals. You can modify your fasting schedule based on your work shifts, personal commitments, and social events. It's crucial to listen to your body and adjust the fasting routine accordingly. For example, if you feel excessively fatigued, you may need to shorten your fasting period or adjust the frequency.

Maintain a Balanced and Healthy Diet During the Feeding Period

Intermittent fasting is not an excuse to indulge in unhealthy foods during the feeding period. The feeding period is crucial for supplying your body with the necessary nutrients to function correctly. It's essential to consume a well-balanced and healthy diet consisting of whole foods, lean protein, complex carbohydrates, healthy fat, and fiber. Stay hydrated by drinking plenty of water and avoid sugary and processed foods that can trigger hunger and disrupt your fasting routine.

Manage Hunger and Cravings Effectively

Hunger and food cravings can be challenging during intermittent fasting, but there are strategies you can use to manage them effectively. For instance, you can distract yourself with hobbies, physical activity, or social interactions. You can also drink water, unsweetened tea or coffee, or a low-calorie beverage to suppress hunger. Snacking during the feeding period is appropriate, as long as it's within your caloric limit and consisting of healthy food choices.

Intermittent fasting can be a successful weight-loss strategy, but it needs to be done right. Choose the right fasting schedule, customize it to your needs, maintain a healthy diet, and manage hunger and cravings effectively to achieve optimal results.


Intermittent fasting has gained popularity as a potential weight loss strategy. It offers many benefits, such as improving metabolic health, reducing the risk of chronic diseases, and promoting cellular repair. However, intermittent fasting is not suitable for everyone and can cause some side effects.

Overview of the Benefits and Drawbacks of Intermittent Fasting

Benefits of Intermittent Fasting:

  • May promote weight loss and reduce body fat
  • Reduces insulin resistance and lowers blood sugar levels
  • Improves metabolic health by reducing oxidative stress and inflammation
  • May reduce the risk of chronic diseases such as heart disease, type 2 diabetes, and cancer
  • May improve brain function and enhance longevity

Drawbacks of Intermittent Fasting:

  • May cause side effects such as headache, lightheadedness, and irritability
  • Requires self-control, discipline, and commitment to the fasting routine
  • Not suitable for everyone, especially pregnant women, people with a history of eating disorders, and those with specific medical conditions

Guidance on the Optimum Approach towards IF

Here are some tips for the optimum approach towards intermittent fasting:

  • Consult with a healthcare provider before starting intermittent fasting, especially if you have any medical conditions or take medications
  • Choose a fasting routine that suits your lifestyle, preferences, and nutritional needs
  • Customize the fasting routine according to your needs and adjust it as necessary
  • Adopt a healthy and balanced diet during the feeding period that supplies your body with the necessary nutrients
  • Practice moderation, and avoid overeating or binge eating during the feeding period
  • Manage hunger and cravings effectively with strategies such as distraction, hydration, and snacking on healthy foods

Final Thoughts on the Efficacy of Intermittent Fasting for Weight Loss

Intermittent fasting can be an effective approach to weight loss, but it's not a magic bullet. It requires self-discipline, commitment, and lifestyle modifications. The success of intermittent fasting depends on various factors such as individual characteristics, fasting routine, dietary choices, and adherence to the plan.

It's essential to consult with a healthcare provider before starting intermittent fasting, especially if you have any medical conditions or take medications. Intermittent fasting may not be suitable for everyone and can cause some side effects and risks.

Overall, intermittent fasting offers potential benefits for weight loss and metabolic health. Still, it's essential to implement it correctly and safely to avoid adverse effects and achieve sustainable results.

William H. McDaniel, MD

Dr. Robert H. Shmerling is the former clinical chief of the division of rheumatology at Beth Israel Deaconess Medical Center (BIDMC), and is a current member of the corresponding faculty in medicine at Harvard Medical School.

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