At 19, I weighed 185 pounds and had tried everything: keto, juice cleanses, the cabbage soup diet (yes, really). Every time I lost weight, I gained it back — plus a few extra pounds for my trouble.

Then I discovered the science of energy balance. Not a fad. Not a shortcut. Just math that actually works. I lost 35 pounds in 8 months, kept it off through grad school, pregnancy, and a decade of life, and now I teach this to clients every day.

This guide is the calorie deficit explanation I wish someone had given me at 19.

How Many Calories to Lose Weight?

Calculate Your Daily Calories →

Use our free calorie calculator to instantly determine your daily calorie needs for weight loss, maintenance, or muscle gain. You can also check your TDEE (Total Daily Energy Expenditure) for more detailed insights.

A calorie deficit occurs when you consume fewer calories than your body burns. To lose 1 pound (0.45 kg) of body fat per week, you need a deficit of approximately 500 calories per day (3,500 calories per week). For example, if your body burns 2,200 calories daily, eating 1,700 calories creates a 500-calorie deficit, resulting in steady, sustainable weight loss.

Tip

Start with a moderate deficit of 300-500 calories per day. When I was losing weight, I made the mistake of cutting 1,200 calories at first. I was exhausted, cranky, and quit after 3 weeks. A 450-calorie deficit felt almost easy by comparison — and I actually stuck with it.

What is a Calorie Deficit?

A calorie deficit is the foundation of all weight loss. According to the National Institutes of Health, when you consume fewer calories than your body needs for daily functions and activities, it must use stored energy (primarily body fat) to make up the difference.

Your body burns calories through three main processes:

Basal Metabolic Rate (BMR): Calories burned at complete rest (60-70% of total)
Thermic Effect of Food (TEF): Calories burned digesting food (10% of total)
Physical Activity: Calories burned through movement and exercise (20-30% of total)

For a detailed explanation of how your body burns calories at rest, see our guide: Understanding Your BMR (Basal Metabolic Rate)

The combination of these three factors is your Total Daily Energy Expenditure (TDEE) - the total number of calories you burn in a day. To lose weight, you must consume fewer calories than your TDEE.

How to Calculate Your Calorie Deficit

Calculating the right calorie deficit involves two steps: finding your TDEE and subtracting an appropriate amount.

Step 1: Calculate Your TDEE

Your TDEE (Total Daily Energy Expenditure) represents all calories burned in a day. For a complete guide on calculating your TDEE, see: TDEE Calculator: How to Calculate Your Daily Calorie Burn

Quick TDEE Estimate:

Activity Level	Multiplier	Example (BMR 1,600)
Sedentary (desk job, little exercise)	BMR × 1.2	1,920 calories
Lightly Active (1-3 workouts/week)	BMR × 1.375	2,200 calories
Moderately Active (3-5 workouts/week)	BMR × 1.55	2,480 calories
Very Active (6-7 workouts/week)	BMR × 1.725	2,760 calories
Extremely Active (athlete)	BMR × 1.9	3,040 calories

Step 2: Choose Your Deficit Level

Once you know your TDEE, subtract calories to create your deficit:

Deficit Level	Daily Deficit	Weekly Loss	Best For
Small	250 calories	0.5 lb (0.23 kg)	Long-term sustainability, athletes
Moderate	500 calories	1 lb (0.45 kg)	Most people, balanced approach
Aggressive	750 calories	1.5 lb (0.68 kg)	Short-term, supervised programs
Extreme	1,000+ calories	2+ lb (0.9 kg)	Not recommended for most people

Example Calculation

Let's calculate the ideal deficit for Sarah, a 35-year-old woman:

Weight: 170 lbs (77 kg)
Height: 5'5" (165 cm)
Activity: Lightly active (works out 3x/week)
BMR: 1,480 calories
TDEE: 1,480 × 1.375 = 2,035 calories

For 1 lb/week weight loss:

Target calories: 2,035 - 500 = 1,535 calories/day

Important

Never go below 1,200 calories (women) or 1,500 calories (men) without medical supervision. Very low calorie diets can cause nutrient deficiencies, muscle loss, and metabolic slowdown.

How Much Weight Can You Lose?

Weight loss rate depends on your deficit size and starting point. Here's what realistic progress looks like:

Safe Weekly Weight Loss Rates:

1% of body weight per week is the maximum recommended for most people
A 200 lb person: up to 2 lbs/week
A 150 lb person: up to 1.5 lbs/week

Realistic Timeline:

Starting Weight	Goal	Weekly Loss	Time to Goal
200 lbs → 170 lbs	30 lbs	1-1.5 lbs	20-30 weeks
180 lbs → 160 lbs	20 lbs	1 lb	20 weeks
160 lbs → 145 lbs	15 lbs	0.5-1 lb	15-30 weeks

Info

The scale isn't everything. Water weight, muscle gain, hormonal fluctuations, and digestive contents can cause daily weight swings of 2-5 lbs. Focus on weekly averages and long-term trends.

Creating Your Deficit: Eat Less vs. Move More

You can create a calorie deficit through diet, exercise, or a combination of both.

Option 1: Diet Only

500-calorie deficit through eating less:

Skip the 300-calorie morning latte
Choose grilled chicken (200 cal) instead of fried (400 cal)
Use a smaller plate to reduce portions by 20%

Pros: Faster results, doesn't require gym time Cons: Can feel restrictive, may lose more muscle

Option 2: Exercise Only

500-calorie deficit through exercise:

60 minutes of brisk walking: 300 calories
30 minutes of running: 400 calories
45 minutes of cycling: 350 calories

Pros: Can eat more, builds muscle, improves fitness Cons: Time-consuming, easy to overeat, can increase hunger

Option 3: Combined Approach (Recommended)

500-calorie deficit through diet + exercise:

Eat 300 fewer calories
Burn 200 extra calories through exercise

Pros: Most sustainable, preserves muscle, flexible approach Cons: Requires tracking both food and activity

Tip

The 80/20 rule works well for most people. Get 80% of your deficit from diet and 20% from exercise. This makes weight loss more manageable without excessive food restriction or workout demands.

What to Eat in a Calorie Deficit

When calories are limited, food quality becomes crucial. Focus on foods that keep you full and satisfied.

High-Satiety Foods (Eat More)

Food Category	Examples	Why They Work
Lean Protein	Chicken, fish, eggs, Greek yogurt	Keeps you full longer, preserves muscle
Vegetables	Broccoli, spinach, peppers, zucchini	High volume, very low calories
Whole Grains	Oats, quinoa, brown rice	Fiber slows digestion
Legumes	Lentils, beans, chickpeas	Protein + fiber combination
Fruits	Berries, apples, oranges	Natural sweetness, fiber

For detailed guidance on protein intake during weight loss, see: Protein Intake Guide: How Much Protein Do You Really Need?

Low-Satiety Foods (Limit)

Food Category	Examples	Why to Limit
Liquid Calories	Sodas, juices, alcohol	No satiety, easy to overconsume
Ultra-Processed	Chips, cookies, fast food	Engineered to make you eat more
Refined Carbs	White bread, pastries	Spike blood sugar, then crash
High-Fat Snacks	Cheese, nuts (in excess)	Calorie-dense, easy to overeat

Sample Day at 1,500 Calories

Meal	Food	Calories
Breakfast	2 eggs, 1 slice whole wheat toast, 1 cup spinach	280
Snack	Greek yogurt (150g) with berries	150
Lunch	Grilled chicken salad with olive oil dressing	400
Snack	Apple with 1 tbsp almond butter	170
Dinner	Salmon (150g), roasted vegetables, quinoa (½ cup)	500
Total		1,500

For a complete guide on tracking your macronutrients, see: Macro Tracking Guide: Count Macros for Better Results

Common Mistakes and How to Avoid Them

Mistake 1: Deficit Too Large

Problem: Cutting too many calories leads to muscle loss, metabolic adaptation, extreme hunger, and eventual binging.

Solution: Start with a moderate 300-500 calorie deficit. If you're constantly hungry, tired, or losing more than 1% of body weight weekly, reduce your deficit.

Mistake 2: Not Counting Accurately

Problem: Studies show people underestimate calorie intake by 30-50%. That "500-calorie" meal might actually be 800 calories.

Solution: Use a food scale for at least 2 weeks to learn portion sizes. Track everything, including cooking oils, sauces, and beverages.

Mistake 3: Weekend Overeating

Problem: A 500-calorie daily deficit (Mon-Fri) can be wiped out by two days of overeating (Sat-Sun).

Weekly Example:

Monday-Friday: 1,500 cal × 5 = 7,500 calories
Saturday: 2,800 calories (party, drinks)
Sunday: 2,500 calories (brunch, comfort food)
Weekly total: 12,800 calories
Daily average: 1,829 calories (no deficit!)

Solution: Plan for flexibility. Save calories during the week for weekend events, or practice moderation rather than restriction.

Mistake 4: Ignoring Protein

Problem: Low protein intake during a deficit leads to muscle loss, slower metabolism, and increased hunger.

Solution: Aim for 0.7-1g of protein per pound of body weight. A 160 lb person needs 112-160g of protein daily.

Warning

Muscle loss slows your metabolism permanently. Protecting muscle mass during weight loss is crucial for long-term success. Prioritize protein and resistance training.

Mistake 5: Expecting Linear Progress

Problem: Weight loss isn't linear. Plateaus, fluctuations, and stalls are normal and don't mean your diet isn't working.

Solution: Focus on 4-week averages, not daily weigh-ins. If you've truly stalled for 3+ weeks, adjust calories down by 100-200 or increase activity slightly.

When to Adjust Your Deficit

Your calorie needs decrease as you lose weight. A 200 lb person burns more calories than a 160 lb person doing the same activities.

Signs You Need to Adjust

Weight loss has stalled for 3+ weeks (and you're tracking accurately)
You've lost 10+ lbs since starting
Your activity level has changed significantly

How to Recalculate

Recalculate your BMR with your new weight
Multiply by activity factor to get new TDEE
Subtract your deficit for new target calories

Example:

Starting: 180 lbs, TDEE 2,400, eating 1,900 (500 deficit)
After 20 lbs lost: 160 lbs, new TDEE ~2,200
New target: 1,700 calories for same 500-calorie deficit

For help determining your goal weight, see: Ideal Weight Guide: How to Find Your Target Weight

Maintaining Your Progress

Weight maintenance is where most diets fail. After reaching your goal, you must transition carefully.

Reverse Dieting

Instead of immediately returning to higher calories, add them back gradually:

Week 1-2: Add 100 calories
Week 3-4: Add another 100 calories
Continue until reaching maintenance TDEE

This approach helps prevent rapid weight regain and gives your metabolism time to adjust.

Long-Term Habits

Continue tracking (at least periodically) to stay aware
Keep protein high to maintain muscle
Stay active - exercise prevents weight regain
Weigh yourself weekly to catch small gains early
Have a plan for when weight creeps up

Success

Maintenance is a lifelong practice, not a destination. People who maintain weight loss successfully treat it as an ongoing process, not something they "finish."

Frequently Asked Questions

How long does it take to see results from a calorie deficit?

You may notice changes in 1-2 weeks, but visible results typically take 4-8 weeks. Water weight changes can mask fat loss initially, so take progress photos and measurements alongside weighing yourself.

Can you lose weight without counting calories?

Yes, but it's less precise. Strategies like portion control, mindful eating, and eliminating processed foods can create a natural deficit. However, counting calories is more reliable for consistent results.

Is 1,200 calories enough?

For most adults, 1,200 calories is the absolute minimum and often too low. Very low calorie diets should only be followed under medical supervision. Most women should aim for 1,400-1,600 minimum; men should aim for 1,600-1,800 minimum.

Why am I not losing weight in a calorie deficit?

Common reasons include: inaccurate calorie tracking, underestimating portions, not counting liquid calories, weekend overeating, or metabolic adaptation. Try tightening your tracking accuracy before cutting calories further.

Should I eat back exercise calories?

Generally, no. Exercise calorie estimates are often inflated by 20-50%. If you do eat back some calories, start with eating only half of what your tracker estimates you burned.

How do I know if my deficit is too aggressive?

Warning signs include: constant hunger, fatigue, irritability, poor sleep, hair loss, loss of menstrual cycle (women), decreased strength in the gym, and thinking about food constantly.

Conclusion

A calorie deficit is the foundation of weight loss, but the key is creating a sustainable deficit you can maintain. Start with a moderate 300-500 calorie deficit, prioritize protein to preserve muscle, and adjust as you progress.

Use our Calorie Calculator to determine your personalized daily calorie target. Combine this with our TDEE Calculator for a complete picture of your energy needs.

Remember: the best deficit is one you can stick to long-term. Consistency over months will always beat perfection over days.