Going on a calorie deficit means consistently eating fewer calories than your body burns, forcing it to tap into stored energy (mostly fat) to make up the difference. The CDC recommends aiming for a pace of 1 to 2 pounds of weight loss per week, which generally requires a daily deficit of 300 to 700 calories below your maintenance level. Getting there involves three steps: figuring out how many calories you currently burn, deciding how large a deficit to create, and structuring your eating and activity to sustain it.
Estimate Your Maintenance Calories
Your body burns calories just keeping you alive: pumping blood, breathing, maintaining body temperature. This baseline burn is your basal metabolic rate, or BMR. The most widely used formula to estimate it is the Harris-Benedict equation, which factors in your weight, height, age, and sex. For men: BMR equals 88 plus (13.4 times your weight in kilograms) plus (4.8 times your height in centimeters) minus (5.7 times your age). For women: BMR equals 448 plus (9.2 times your weight in kilograms) plus (3.1 times your height in centimeters) minus (4.3 times your age).
BMR only covers what your body burns at complete rest. To get your total daily energy expenditure, you multiply BMR by an activity factor. A sedentary person (desk job, little exercise) multiplies by about 1.2. Someone who exercises moderately three to five days a week multiplies by roughly 1.55. Very active people use 1.7 or higher. The result is your estimated maintenance calories, the number where your weight stays roughly stable.
These formulas give you a starting point, not a precise number. Genetics, muscle mass, sleep quality, and hormones all influence your actual burn rate. Treat the calculation as a first estimate, then adjust based on what the scale and your energy levels tell you over two to three weeks.
Choose the Right Size Deficit
You’ve probably heard the old rule that cutting 500 calories a day produces one pound of weight loss per week, based on the idea that a pound of fat contains 3,500 calories. The Mayo Clinic notes this rule doesn’t hold equally for everyone. Your body adapts to a deficit over time, so weight loss slows even if your intake stays the same. A more realistic approach is to start with a moderate deficit of 300 to 500 calories per day, monitor your results for two to three weeks, and adjust from there.
There are important floors to respect. Harvard Health recommends women eat no fewer than 1,200 calories per day and men no fewer than 1,500, unless supervised by a healthcare professional. Dropping below those thresholds makes it very difficult to get adequate vitamins, minerals, and protein, and it increases the risk of gallstones, muscle loss, and hormonal disruption.
Why Your Body Fights Back
When you cut calories, your metabolism doesn’t just hum along at the same rate. Your body reduces its energy expenditure beyond what you’d expect from the weight you’ve lost. Research published in ScienceDirect found this adaptive response kicks in within the first week of dieting, averaging about 178 calories per day less burned than predicted. That means if two people have the same stats but one’s body adapts more aggressively, that person could lose roughly 2 kilograms (about 4.4 pounds) less over six weeks on the same diet.
This is one reason aggressive deficits often backfire. Larger calorie cuts trigger a stronger adaptive response, making it harder to sustain progress and easier to regain weight when you return to normal eating. A moderate deficit gives your metabolism less reason to slam the brakes.
Prioritize Protein
When you eat below maintenance, your body doesn’t exclusively burn fat. It also breaks down muscle for energy, especially if protein intake is low. The standard recommended dietary allowance for protein is 0.8 grams per kilogram of body weight per day, but research in Frontiers in Nutrition suggests that’s not enough to protect muscle mass. An intake of 1.0 to 1.2 grams per kilogram of body weight per day is more effective for preserving lean tissue and strength.
For a 170-pound (77 kg) person, that translates to roughly 77 to 92 grams of protein daily. Spreading it across three or four meals helps your body use it more efficiently than loading it all into one sitting. Protein also keeps you fuller for longer, which makes the deficit itself easier to stick with. Good sources include chicken, fish, eggs, Greek yogurt, beans, lentils, and tofu.
Use Exercise to Widen the Gap
You can create a deficit entirely through food, entirely through exercise, or through a combination of both. Most people find a mix works best because it means smaller dietary restrictions. A 300-calorie food reduction paired with a 200-calorie walk gets you to a 500-calorie deficit without feeling deprived at meals.
Resistance training deserves special attention during a deficit. The Cleveland Clinic points out that muscle tissue burns more calories than other body tissue even at rest, so building or maintaining muscle through strength training raises your daily calorie burn around the clock. Cardio is useful for burning calories during the session itself, but it doesn’t offer the same lasting metabolic benefit. A practical split is two to three strength sessions per week alongside whatever cardio you enjoy, whether that’s walking, cycling, or swimming.
Don’t overlook everyday movement either. The calories you burn through non-exercise activity (walking to the store, cleaning, fidgeting, taking stairs) can vary by several hundred calories a day between people. Parking farther away, standing during phone calls, and taking short walking breaks all add up without requiring gym time.
Track Without Obsessing
Food tracking is the most reliable way to know whether you’re actually in a deficit. Apps that scan barcodes or let you search a database make this relatively painless. You don’t need to weigh every grain of rice forever. Most people benefit from tracking carefully for two to four weeks to learn what portions actually look like, then transitioning to a more intuitive approach once they have a feel for it.
Weigh yourself at the same time each day (morning, after using the bathroom) and look at the weekly average rather than any single reading. Daily weight can swing 1 to 3 pounds based on water retention, sodium intake, and digestion. If your weekly average trends downward by 0.5 to 1 percent of your body weight, you’re on track. If it stalls for more than two weeks, reduce your daily intake by another 100 to 150 calories or add a bit more activity.
Common Mistakes That Stall Progress
- Underestimating liquid calories. Coffee drinks, juices, alcohol, and smoothies can add 200 to 600 calories a day without registering as a “meal.” Track these like any other food.
- Cutting too aggressively. A 1,000-calorie daily deficit sounds faster, but it accelerates metabolic adaptation, increases muscle loss, and usually leads to a hard rebound. Moderate and consistent beats extreme and short-lived.
- Ignoring sleep. Poor sleep raises hunger hormones and lowers the hormones that signal fullness. Even a well-designed deficit becomes harder to maintain on five or six hours of sleep per night.
- Weekend overconsumption. Five days at a 500-calorie deficit creates a 2,500-calorie gap. Two weekend days of eating 1,000 calories over maintenance erases most of it. Consistency across the full week matters more than perfection on weekdays alone.
- Skipping protein at breakfast. Starting the day with carbs alone (cereal, toast, juice) often leads to stronger hunger and larger portions later. A protein-rich first meal helps regulate appetite through the afternoon.
A Simple Starting Framework
Calculate your estimated maintenance calories using the BMR formula and an activity multiplier. Subtract 300 to 500 calories. Make sure the result stays above 1,200 (women) or 1,500 (men). Aim for at least 1.0 gram of protein per kilogram of body weight. Fill the rest of your calories with vegetables, whole grains, fruits, and healthy fats. Add two to three strength training sessions per week and stay as active as you can outside the gym.
Give any new plan at least three weeks before evaluating. Early weight loss in the first week is mostly water, not fat, and doesn’t reflect your true rate of progress. By week three or four, the trend line becomes meaningful. If you’re losing 1 to 2 pounds per week and your energy levels feel manageable, you’ve found a sustainable deficit.