Belly fat is a common concern for many people. Excess abdominal fat not only causes clothing to feel tighter and look less flattering, but it’s also associated with serious health risks like heart disease, type 2 diabetes, and certain cancers. For these reasons, burning belly fat is often a top priority among those looking to reach better health and physique goals.
There are many strategies that aim to reduce belly fat, including diet, exercise, and lifestyle changes. One increasingly popular approach is intermittent fasting, which involves cycling between periods of fasting and eating. Proponents claim that intermittent fasting can target stubborn belly fat and promote fat loss.
This article reviews the research to determine whether intermittent fasting burns belly fat.
What is intermittent fasting?
Intermittent fasting is an eating pattern that cycles between periods of fasting and eating. Rather than restrict what you eat, it dictates when you should eat.
There are several forms of intermittent fasting, including:
- The 16/8 method: Fast for 16 hours per day and eat all meals within an 8-hour window.
- The 5:2 diet: Eat normally 5 days per week and limit calories to 500–600 on 2 days.
- Alternate-day fasting: Fast every other day, limiting intake to 500–600 calories on fasting days.
- The Warrior Diet: Eat small amounts of raw fruits and vegetables during the day and one huge meal at night.
- Time-restricted fasting: Eat all calories within a set window, usually 4–10 hours per day.
The most popular form of intermittent fasting is the 16/8 method, which involves skipping breakfast and restricting eating to an 8-hour window, such as 12–8 p.m. or 1–9 p.m.
How intermittent fasting affects belly fat
Intermittent fasting may help reduce belly fat in several ways:
Increases fat burning
Intermittent fasting transitions the body from burning sugar to fat as its primary fuel source. This increases fat burning, especially of belly fat stores. One study found that 16 hours of intermittent fasting for 12 weeks decreased body fat mass by 7–12 pounds (3.2–5.5 kg) and belly fat by 4–7% (1).
Reduces calorie intake
Intermittent fasting leads to an automatic reduction in calorie intake because it limits eating to certain hours of the day. One study noted that intermittent fasting resulted in up to 22% fewer calories eaten per day (2). Decreasing overall calorie intake creates a calorie deficit needed for fat and weight loss.
May prevent muscle loss
Some fat loss strategies spur muscle loss alongside fat loss, but research shows that intermittent fasting is muscle-sparing. This indicates that intermittent fasting preferentially targets fat cells — including belly fat — over muscle tissue (1).
Boosts metabolism
Studies demonstrate that intermittent fasting increases your resting metabolic rate (RMR). This refers to the number of calories your body burns at rest. One review found that intermittent fasting boosted RMR by 3–14%, compared to only 3–4% for other diets (3). A higher RMR burns more calories around the clock, enhancing fat loss.
May suppress hunger hormones
Intermittent fasting reduces levels of the hunger hormone ghrelin. It also increases levels of peptide YY, a hormone that contributes to appetite control (2, 4). These changes promote satiety and help you eat fewer calories.
Other benefits of intermittent fasting
Beyond belly fat reduction, intermittent fasting offers additional benefits:
- Easier weight management: Simpler than counting calories
- Increased insulin sensitivity: Helps regulate blood sugar
- Lower inflammation: Associated with health problems
- Improved heart health: Reduces heart disease risk factors
- Anti-aging effects: May extend lifespan
Effective intermittent fasting protocols
The most effective intermittent fasting protocols for fat loss involve daily fasting windows of 14–16 hours or fasting durations of at least 16 hours 2–4 times per week. Longer, less frequent fasts appear equally effective (1).
Popular plans fitting these criteria include:
- 16/8 method: Fast for 16 hours, eat for 8 hours daily
- Alternate-day fasting: Fast every other day
- 5:2 diet: Restrict calories to 500–600 two days weekly
Tips to maximize belly fat loss
Here are some tips to optimize intermittent fasting for fat loss:
Pair with a healthy diet
Eat minimally processed foods like fruits, veggies, lean protein, whole grains, and healthy fats during eating periods.
Stay hydrated
Drink water, unsweetened coffee, tea, and other zero-calorie beverages during fasts.
Exercise
Perform aerobic and strength training workouts to enhance fat burning.
Get enough sleep
Aim for 7–9 hours per night to support fat loss and prevent hunger hormones from rising.
Reduce stress
High stress raises cortisol, which encourages belly fat accumulation.
Downsides of intermittent fasting
Despite its benefits, intermittent fasting has some downsides to consider:
- Hunger: Difficult for some people, especially at first
- Headaches: Especially when first starting
- Dizziness: Due to low blood sugar
- Difficulty sleeping: Can disrupt circadian rhythm
- Social challenges: Restricted eating times
- Binge eating: Risk for some people
- Reduced athletic performance: Requires adaptation period
Intermittent fasting may also be unsuitable for some populations, including:
- Pregnant or breastfeeding women
- Children and teenagers
- Malnourished individuals
- Those with a history of eating disorders
- People with medical conditions like diabetes or gout
Conclusion
Research indicates that intermittent fasting can be an effective strategy to reduce belly fat. It does this by increasing fat burning, reducing calories, preserving muscle, boosting metabolism, and modifying hunger hormones.
The most successful plans incorporate daily 14–16 hour fasts or fasting for 24+ hours two to four times per week. For best results, pair intermittent fasting with a healthy diet and regular exercise.
However, intermittent fasting may not be right for everyone. Work with a healthcare professional, especially if you have an underlying medical condition or take medications.
With the proper precautions, intermittent fasting can be a sustainable, convenient way to drop belly fat and improve health.
Frequently Asked Questions
How long does it take to see results from intermittent fasting?
You can expect to see some weight loss results within the first week of intermittent fasting. However, noticeable fat loss takes longer, around 3-6 weeks. Maximum fat burning effects are seen after 12 or more weeks of consistent intermittent fasting.
Can you gain weight with intermittent fasting?
It’s possible to gain weight while intermittent fasting if you consume too many calories during eating periods. Be sure to eat healthy portions of nutritious foods.
Is intermittent fasting bad for you?
For most people, intermittent fasting is safe and may offer health benefits related to weight, insulin resistance, inflammation, heart health, and even anti-aging. However, some groups should avoid it, including pregnant women, adolescents, and those with medical conditions or a history of disordered eating.
Can intermittent fasting cause hair loss?
In some cases, intermittent fasting may contribute to temporary hair loss. This is related to changes in nutrition. Hair loss from intermittent fasting is rare and reversible by adjusting your diet or fasting protocol.
Can I drink coffee while intermittent fasting?
Yes, it’s fine to drink black coffee, tea, and other zero-calorie beverages during the fasting period. Avoid adding milk, cream, or caloric sweeteners.
The bottom line
Intermittent fasting transitions your body from burning sugar to fat as fuel. This boosts fat burning, especially of stubborn belly fat, and leads to impressive health benefits.
Research supports intermittent fasting as an efficient tool for decreasing belly fat, along with improving body composition, blood sugar, and other health metrics.
For best results, pair intermittent fasting with a balanced, nutritious diet and regular physical activity. With consistency, intermittent fasting can be a simple, effective way to get rid of belly fat.