How Many Calories Should I Eat If I Am Intermittent Fasting?

December 19, 2025 •

2 min read

According to one study, daily intermittent fasting that restricts eating to a specific window can naturally help people consume about 250 fewer calories a day. So, how many calories should I eat if I am intermittent fasting to align with my specific health goals?

Quick Summary

Calorie needs during intermittent fasting depend on individual goals like weight loss, maintenance, or muscle gain. Calculating your energy needs and focusing on nutrient-dense meals within your eating window is key.

Key Points

Personalized Approach: Your ideal calorie intake for intermittent fasting depends on your unique body metrics, activity level, and goals, not a universal number.
Calculate Your Needs: Use formulas like Mifflin-St Jeor to determine your Basal Metabolic Rate (BMR) and then apply an activity multiplier to find your Total Daily Energy Expenditure (TDEE).
Achieve Your Goal: Create a calorie deficit for weight loss, eat at your TDEE for maintenance, or consume a surplus for muscle gain within your eating window.
Focus on Quality: Prioritize nutrient-dense whole foods like lean proteins, healthy fats, and fiber-rich carbs during your eating periods to ensure adequate nutrition and satiety.
Avoid Overcompensation: The most common mistake is overeating during the eating window. Mindful eating is essential to prevent this and ensure you maintain a calorie deficit if weight loss is the goal.
Stay Hydrated: Drink plenty of water and other zero-calorie beverages during fasting periods to manage hunger, avoid headaches, and maintain hydration.

Your Personal Calorie Needs on Intermittent Fasting

There is no one-size-fits-all answer to the question of how many calories you should eat while intermittent fasting. Your ideal daily calorie target depends on various factors, including your age, gender, weight, height, activity level, and specific goals. While intermittent fasting (IF) naturally helps regulate calorie intake by shortening the eating window, you still need to be mindful of your total consumption to achieve your desired outcome. The principles of energy balance—consuming fewer calories than you burn for weight loss, or more for weight gain—still apply.

How to Calculate Your Calorie Target

The first step to determining your calorie needs is to find your Total Daily Energy Expenditure (TDEE). This is an estimate of the total number of calories you burn in a day, based on your Basal Metabolic Rate (BMR) and activity level. Your BMR is the energy your body needs at rest. The Mifflin-St Jeor formula is commonly used for BMR:

For Men: BMR = (10 x weight in kg) + (6.25 x height in cm) - (5 x age in years) + 5
For Women: BMR = (10 x weight in kg) + (6.25 x height in cm) - (5 x age in years) - 161

Multiply your BMR by an activity factor (ranging from 1.2 for sedentary to 1.9 for extra active) to get your TDEE.

Calorie Goals Based on Your Objective

Adjust your calorie intake from your TDEE based on your goal:

Weight Loss: Consume 500-750 fewer calories than your TDEE for a loss of 1-1.5 pounds per week.
Weight Maintenance: Eat at your TDEE.
Muscle Gain: Consume 250-500 calories more than your TDEE, focusing on protein.

The Importance of Nutrient-Dense Foods

Filling your eating window with nutrient-dense, whole foods is crucial for satiety and preventing deficiencies. Focus on lean proteins, healthy fats, and fiber-rich carbohydrates.

Comparison of Common Intermittent Fasting Methods and Calories


Feature	16:8 Method	5:2 Method	Alternate-Day Fasting (ADF)
Schedule	16 hours of fasting, 8-hour eating window daily	5 days of normal eating, 2 non-consecutive days of calorie restriction	Alternating between 'fast' days and 'normal' eating days
Calorie Guidelines	Eat all daily calories within the 8-hour window; adjust for goals.	Women: ~500 calories on fast days. Men: ~600 calories on fast days.	Eat freely on 'normal' days. Consume ~500 calories or less on 'fast' days.
Flexibility	Highly flexible.	Can choose any two non-consecutive days.	Less flexible due to the every-other-day pattern.
Primary Mechanism	Limits the time for eating, often leading to a natural calorie deficit.	Reduces weekly total calorie intake.	Reduces overall weekly calorie intake more significantly.

Common Pitfalls and How to Avoid Them

Overeating during the eating window is a common mistake. Listen to your body and focus on healthy foods. Initial fatigue is possible but often temporary. Staying hydrated is also important.

Conclusion

Achieving specific goals with intermittent fasting requires attention to calorie intake within the eating window. Calculate your individual needs, prioritize nutritious foods, and maintain consistency. Consult a healthcare professional before significant dietary changes. For more information on dietary needs, see resources like the National Institutes of Health (NIH).

Frequently Asked Questions

Yes, many people can lose weight without meticulous calorie counting. Intermittent fasting naturally leads to a reduced calorie intake by shortening the eating window. However, if weight loss stalls, tracking your calorie intake might become necessary to ensure you are in a deficit.

A sustainable and safe calorie deficit for weight loss while intermittent fasting is typically 500-750 calories below your calculated TDEE. This generally leads to a weight loss of 1-1.5 pounds per week, which helps preserve muscle mass.

On the two fasting days of a 5:2 diet, it is typically recommended that women consume around 500 calories and men consume around 600 calories. On the other five days, you eat normally.

If you consistently overeat during your eating window, you may negate the calorie deficit created by fasting and could experience weight gain. This is a common mistake that can hinder your progress.

To get the most benefit from IF, focus on nutrient-dense, whole foods. These include lean proteins, healthy fats, and fiber-rich carbohydrates from fruits, vegetables, and whole grains.

In time-restricted eating (like 16:8), all your calories are consumed within a single daily window. With alternate-day fasting (ADF), calories are restricted on fasting days (often to 500 or less) but eaten normally on non-fasting days, resulting in a larger deficit on average.

Some research suggests that intermittent fasting may temporarily boost metabolic rate due to increased norepinephrine levels, especially after 12 hours of fasting as the body shifts to burning fat. This is part of the 'metabolic switching' process.