To lose about one pound per week, you need to burn roughly 500 more calories per day than you eat. That’s the most widely recommended starting point, and it works through a simple principle: when your body consistently uses more energy than it takes in, it pulls from stored fat to make up the difference. This gap between what you consume and what you burn is called a calorie deficit, and you can create it by eating less, moving more, or both.
How a Calorie Deficit Actually Works
Your body burns calories around the clock, not just during exercise. The total energy you use in a day breaks down into three categories: your resting metabolism (the calories your organs, brain, and muscles need just to keep you alive), the energy spent digesting food (about 10% of your daily total), and physical activity. For most people, resting metabolism accounts for the largest share, which is why your body size, age, and muscle mass matter so much in this equation.
A 500-calorie daily deficit adds up to about 3,500 calories per week. You may have heard that 3,500 calories equals one pound of fat. That number is a rough estimate, not a law of physics. The Mayo Clinic notes that when you lose weight, you lose a mix of fat, lean tissue, and water, so the math doesn’t play out perfectly for everyone. Still, a 500-calorie deficit is a reliable benchmark for losing roughly one to two pounds per week, which the NIH considers a healthy pace.
The size of your deficit determines your speed. A 100-calorie daily gap will produce noticeably slower results than a 500-calorie gap. But bigger is not always better. Cutting too aggressively can backfire, as your body responds to severe restriction by slowing your metabolism and breaking down muscle along with fat.
Finding Your Personal Calorie Baseline
Before you can figure out how much to burn, you need to know how much your body already burns without any extra effort. This is your resting metabolic rate. The most reliable formula for estimating it, validated in a systematic review published in the Journal of the American Dietetic Association, is the Mifflin-St Jeor equation. It predicted resting metabolism within 10% of the actual measured value for more people (both at a healthy weight and with obesity) than any other commonly used formula.
Here’s the simplified version:
- Men: (10 × weight in kg) + (6.25 × height in cm) – (5 × age) + 5
- Women: (10 × weight in kg) + (6.25 × height in cm) – (5 × age) – 161
That gives you the calories your body burns at complete rest. To estimate your total daily burn, you multiply by an activity factor: 1.2 if you’re mostly sedentary, 1.375 for light activity a few days a week, 1.55 for moderate exercise three to five days, and 1.725 for heavy daily training. The result is a rough estimate of the total calories you burn each day. Subtract 500 from that number, and you have your daily calorie target for losing about a pound a week.
For example, a 40-year-old woman who weighs 170 pounds, stands 5’5″, and exercises lightly might burn around 1,750 calories per day. To create a 500-calorie deficit, she could aim for about 1,250 calories through food, burn an extra 500 through activity, or split the difference.
Why Cutting Calories Beats Burning Them Off
Diet and exercise are not equally efficient at creating a deficit. Reducing what you eat is far easier than trying to burn the same number of calories through movement. As one Mayo Clinic physician put it, you have to do huge amounts of physical activity to lose weight, but you can create a better energy deficit just by cutting down on calories. A 30-minute jog might burn 250 to 350 calories. Skipping a large muffin accomplishes the same thing.
That said, exercise becomes critical once the weight is off. The same Mayo Clinic guidance is clear: diet is probably more important for losing weight, but physical activity is more effective for keeping it off. So the ideal approach uses both, leaning more on food choices during active weight loss and more on movement during maintenance.
The Calories You Burn Without Trying
One of the most underappreciated pieces of your daily calorie burn is non-exercise activity: fidgeting, standing, walking to the kitchen, carrying groceries, taking the stairs. The difference in calories burned through these small movements can be dramatic. Between two people of similar size, daily non-exercise activity can vary by up to 2,000 calories depending on occupation and lifestyle. A construction worker and an office worker with identical body compositions live in completely different metabolic worlds.
Small adjustments add up. Simply increasing the time you spend standing and walking by about two and a half hours per day can boost your burn by roughly 350 calories. That alone could account for most of a 500-calorie deficit without setting foot in a gym. Parking farther away, taking calls while walking, or using a standing desk are low-effort ways to nudge this number higher.
Why Weight Loss Slows Over Time
Almost everyone who loses weight hits a plateau, and it’s not because of a lack of willpower. It’s biology. As you get smaller, your body needs fewer calories to function. You also lose some muscle along with fat during weight loss, and muscle burns more calories at rest than fat does. The result is a slower metabolism that requires fewer calories to maintain your new, lighter body.
This means the same 500-calorie deficit that worked at 200 pounds may only produce a 200-calorie deficit at 180 pounds. Your energy balance is a moving target. To keep losing, you either need to eat a little less, move a little more, or accept a slower rate of loss. Recalculating your calorie needs every 10 to 15 pounds lost helps you stay realistic about your timeline.
Minimum Calories You Shouldn’t Go Below
There is a floor. Harvard Health Publishing advises that women should not eat fewer than 1,200 calories per day and men should not go below 1,500 without medical supervision. Dropping below these thresholds risks nutrient deficiencies that can affect everything from your energy levels to your immune function and bone health. If your calorie math puts your daily intake below these numbers, the safer move is to close the gap with more physical activity rather than further food restriction.
Putting the Numbers Together
Here’s a practical framework for setting your own target:
- Estimate your total daily burn using the Mifflin-St Jeor equation and an activity multiplier.
- Subtract 500 calories to aim for about one pound of loss per week, or 250 for a more gradual half-pound pace.
- Split the deficit between eating less and moving more. Cutting 300 calories from food and burning 200 through exercise is more sustainable than doing either one alone.
- Recalculate every 10 to 15 pounds to account for your changing metabolism.
- Stay above the floor: 1,200 calories daily for women, 1,500 for men.
Weight loss is not a single math problem you solve once. It’s a series of adjustments as your body changes. The 500-calorie deficit is where most people should start, but the number that matters most is the one that lets you stay consistent week after week without feeling deprived enough to quit.