How many calories to eat while intermittent fasting 16:8?

October 15, 2025 •

4 min read

Recent studies suggest that time-restricted eating, like the 16:8 method, can lead to a natural reduction in daily calorie intake. However, the crucial question remains: how many calories to eat while intermittent fasting 16:8 to achieve your specific health goals, such as weight loss or maintenance, without compromising nutrition.

Quick Summary

The ideal calorie intake during 16:8 intermittent fasting depends on individual factors like age, gender, and activity level. Calorie counting is not mandatory but can help create a deficit for weight loss, emphasizing nutrient-dense foods within the 8-hour eating window. Avoid over-restricting calories to prevent nutrient deficiencies and metabolic slowdown.

Key Points

Calculate Personalized Needs: There is no universal number of calories to eat; calculate your personal Basal Metabolic Rate (BMR) and Total Daily Energy Expenditure (TDEE) to determine your baseline needs.
Adjust for Your Goals: For weight loss, aim for a moderate calorie deficit of 500–750 calories below your TDEE during your 8-hour window. For maintenance, consume calories equal to your TDEE.
Focus on Nutrient-Dense Foods: The quality of food matters significantly. Prioritize lean proteins, healthy fats, whole grains, and a variety of fruits and vegetables to ensure satiety and adequate nutrition.
Avoid Overeating or Extreme Restriction: Overcompensating with junk food during the eating window negates benefits, while overly restricting calories can harm metabolism and lead to nutrient deficiencies.
Prioritize Hydration: Drinking plenty of calorie-free fluids like water, black coffee, and herbal tea is vital for curbing hunger and staying hydrated, especially during the 16-hour fast.
Listen to Your Body: Pay attention to hunger and fatigue cues. The plan should be sustainable, not miserable. Adjusting your eating window or calorie intake is okay if needed.

Understanding the 16:8 Method

Intermittent fasting (IF), specifically the 16:8 method, is a pattern of eating that cycles between a period of fasting and a period of eating. In this case, you consume all your daily food within an 8-hour window and fast for the remaining 16 hours. Unlike traditional diets that focus heavily on what you eat, the 16:8 method primarily emphasizes when you eat. For many, this structured eating schedule naturally leads to a moderate reduction in overall calorie intake, which can support weight loss. However, simply restricting the eating window isn't a guarantee of success if the quality and quantity of food consumed during that time are not managed effectively.

The Calculation: Determining Your Calorie Needs

The number of calories you should consume during your 16:8 eating window is not a one-size-fits-all number. It is highly personalized and depends on several factors, including your age, gender, weight, height, and activity level. A good starting point is to calculate your daily energy expenditure using a two-step process:

Calculate your Basal Metabolic Rate (BMR): This is the number of calories your body needs to perform basic, life-sustaining functions at rest. The Mifflin-St. Jeor equation is a widely used formula:
- Men: $(10 × ext{weight in kg}) + (6.25 × ext{height in cm}) - (5 × ext{age in years}) + 5$
- Women: $(10 × ext{weight in kg}) + (6.25 × ext{height in cm}) - (5 × ext{age in years}) - 161$
Determine your Total Daily Energy Expenditure (TDEE): This accounts for your daily activity level. Multiply your BMR by an activity factor:
- Sedentary: BMR × 1.2 (little or no exercise)
- Lightly Active: BMR × 1.375 (light exercise 1–3 days/week)
- Moderately Active: BMR × 1.55 (moderate exercise 3–5 days/week)
- Very Active: BMR × 1.725 (hard exercise 6–7 days/week)
- Extra Active: BMR × 1.9 (very hard exercise, physical job)

Calorie Targets for Different Goals

Your TDEE is the number of calories you need to consume to maintain your current weight. Your specific calorie target during your 16:8 eating window will depend on your goal:

Weight Loss: To lose weight, you must create a calorie deficit. A moderate deficit of 500–750 calories per day is generally safe and effective for losing 1–1.5 pounds per week. For example, if your TDEE is 2,000 calories, you would aim for 1,250–1,500 calories within your 8-hour window.
Weight Maintenance: If your goal is to maintain your current weight, you should aim to consume your TDEE within the eating window.
Muscle Gain: For those looking to build muscle, a calorie surplus is required. However, achieving a significant surplus within an 8-hour window can be challenging and may lead to digestive issues for some. It is crucial to prioritize protein intake in this case.

The Importance of Nutrient-Dense Foods

Regardless of your calorie goal, the quality of the food you eat is paramount. Simply restricting the eating window and then consuming processed, high-sugar, or high-fat foods can negate the health benefits of fasting. Focusing on nutrient-dense, whole foods is essential for maintaining energy, satiety, and overall health.

Food Categories for a 16:8 Diet:

Lean Proteins: Chicken, fish, tofu, legumes, and eggs are crucial for muscle maintenance and satiety.
Healthy Fats: Sources like avocados, olive oil, nuts, and seeds support heart health and can help you feel full longer.
Whole Grains: Quinoa, oats, brown rice, and whole-grain bread provide fiber and sustained energy.
Fruits and Vegetables: A wide variety of colorful produce provides essential vitamins, minerals, and fiber.

Comparison of 16:8 Goals and Caloric Needs


Goal	Target Calorie Consumption	Meal Composition Focus	Considerations
Weight Loss	TDEE minus 500–750 calories	High protein, high fiber, healthy fats to promote satiety and reduce overall intake	Avoid extremes; consuming less than 1,200 calories can slow metabolism.
Weight Maintenance	Consume calories equal to TDEE	Balanced meals with whole foods to support energy and health without overeating	Consistent, nutrient-rich meals within the window prevent fluctuations.
Muscle Gain	TDEE plus a surplus (may be difficult to achieve within 8 hours)	High protein intake, timed around workouts for recovery and muscle protein synthesis	May not be optimal for rapid muscle mass gain due to restricted feeding window.

Common Pitfalls and How to Avoid Them

While the 16:8 method is generally safe and sustainable for most healthy adults, it's not without potential pitfalls. Being mindful of these can increase your chances of long-term success:

Overeating during the eating window: The most common mistake is overcompensating for the fasting period by binge-eating high-calorie, processed foods, which can lead to weight gain instead of loss.
Not eating enough: Severely restricting calories below your body's needs can lead to a slowed metabolism, nutrient deficiencies, and muscle mass loss. For most women, intake should not drop below 1,200 calories.
Forgetting hydration: Staying hydrated is critical, especially during the fasting window. Calorie-free beverages like water, black coffee, and unsweetened tea are key.
Ignoring your body's signals: Listen to your body. Intense hunger, dizziness, or fatigue are signs to reassess your plan.

Conclusion

Determining how many calories to eat while intermittent fasting 16:8 is a personalized process that requires calculating your baseline energy needs and adjusting based on your goals. For weight loss, a moderate calorie deficit is key, while maintenance requires matching your TDEE. Regardless of your objective, focusing on nutrient-dense whole foods and staying hydrated is essential for success. Always listen to your body and consult a healthcare provider, especially if you have underlying health conditions. By combining the timing aspect of 16:8 with smart nutritional choices, you can effectively manage your diet and work towards your health goals in a sustainable way.

For more detailed nutritional advice, consulting a registered dietitian is highly recommended to tailor a plan to your unique needs.

Frequently Asked Questions

The 16:8 method involves fasting for 16 continuous hours and consuming all your food and calorie-containing beverages during a specific 8-hour window each day.

While calorie counting isn't explicitly required, managing your intake is necessary to achieve weight loss. The 16:8 method itself can lead to a natural calorie reduction, but consciously creating a deficit is needed for more targeted results.

First, calculate your TDEE (Total Daily Energy Expenditure) based on your BMR and activity level. Then, for a moderate weight loss, subtract 500–750 calories from your TDEE to determine your target intake within the 8-hour window.

Focus on nutrient-dense, whole foods such as lean proteins, healthy fats, whole grains, and plenty of fruits and vegetables. These foods provide sustained energy and help keep you full.

Consuming anything with calories will technically break your fast. Stick to calorie-free beverages like water, black coffee, and plain herbal tea during your fasting period.

Gaining significant muscle mass can be challenging on 16:8 fasting because it's difficult to achieve a large calorie surplus within the 8-hour window. It is important to prioritize adequate protein intake if this is your goal.

Initial side effects can include hunger, fatigue, and headaches as your body adjusts. Overeating or undereating during the eating window can also lead to digestive issues or nutrient deficiencies.