A calorie deficit means consuming fewer calories than your body burns in a day. To create one, you need two pieces of information: how many calories you currently burn and a plan to consistently stay below that number through eating less, moving more, or both. A deficit of 500 calories per day is the most common starting point, producing roughly one to two pounds of weight loss per week.
Estimate How Many Calories You Burn
Your body burns calories through three main channels: keeping you alive at rest (breathing, circulating blood, repairing cells), digesting food, and physical movement. The first category, your basal metabolic rate, accounts for the largest share. The most widely used formula for estimating it is the Mifflin-St Jeor equation, which uses your weight in kilograms, height in centimeters, age, and sex:
- Men: (10 × weight) + (6.25 × height) – (5 × age) + 5
- Women: (10 × weight) + (6.25 × height) – (5 × age) – 161
That result is just your resting burn. To get your total daily energy expenditure, you multiply it 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 activity, 1.725 for daily hard exercise, and 1.9 for very intense physical jobs or training. Most people with desk jobs who exercise a few times a week fall in the 1.375 to 1.55 range.
As an example, a 35-year-old woman who weighs 70 kg (154 lbs), is 165 cm (5’5″), and exercises lightly would have a resting rate of about 1,399 calories. Multiplied by 1.375, her estimated daily burn is roughly 1,924 calories. To lose about a pound a week, she’d aim to eat around 1,424 calories per day.
Set Your Deficit Size
The CDC notes that people who lose weight at a gradual pace of one to two pounds per week are more likely to keep it off than those who lose faster. You may have heard that cutting 3,500 calories produces one pound of fat loss. The Mayo Clinic points out this old rule isn’t accurate for everyone, because weight loss involves a mix of fat, lean tissue, and water, and your body’s calorie needs shift as you shrink. Still, a daily deficit of 500 calories is a practical starting target for most people.
There’s also a floor to respect. Harvard Health recommends women don’t go below 1,200 calories per day and men don’t go below 1,500 without medical supervision. Dropping too low deprives your body of essential nutrients and can trigger the exact metabolic slowdown you’re trying to avoid.
Why Your Body Fights Back
When you stay in a calorie deficit for weeks, your body doesn’t just passively lose weight. It actively resists. Your energy expenditure drops more than the lost weight alone would predict, a phenomenon researchers call adaptive thermogenesis. Hormones that regulate your metabolism, appetite, and fat storage (including thyroid hormones and leptin) shift in ways that conserve energy and increase hunger.
This is why weight loss often stalls after several weeks even if you haven’t changed anything. It’s not a willpower failure. It’s your metabolism recalibrating. The practical response is to periodically reassess your calorie target as you lose weight, since a smaller body burns fewer calories. Some people also benefit from scheduled “diet breaks,” eating at maintenance for a week or two before returning to a deficit, to partially reset these signals.
Move More (Especially Without “Exercising”)
Formal exercise gets most of the attention, but the calories you burn outside the gym through everyday movement often matter more. This category, called non-exercise activity thermogenesis, includes walking, fidgeting, standing, cooking, cleaning, and taking the stairs. According to Mayo Clinic research, NEAT can account for a difference of up to 2,000 calories per day between two people of the same size. An active job alone can burn 1,000 more calories daily than a sedentary one.
You don’t need to run marathons to widen your deficit. Small changes add up: walking after meals, standing while on phone calls, gardening in the evening instead of watching TV (the difference between those two activities can be roughly 570 calories). If you sit at a desk all day, even getting up every 30 minutes for a few minutes of movement shifts your daily burn meaningfully over time.
Structured exercise still helps, of course. Resistance training is particularly valuable during a deficit because it signals your muscles to stick around rather than get broken down for energy.
Eat to Stay Full on Fewer Calories
The biggest challenge of a calorie deficit isn’t math. It’s hunger. The foods you choose determine whether a 1,600-calorie day feels comfortable or miserable.
Research on energy density shows that people tend to eat a similar weight of food each day regardless of calorie content. This means you can eat the same physical volume of food while taking in fewer calories by choosing foods that are heavier but lower in energy: vegetables, fruits, soups, legumes, and lean proteins. A plate piled with roasted broccoli, chicken breast, and sweet potato looks and feels like a full meal but may contain half the calories of a smaller-looking plate of pasta with cream sauce.
Fiber plays a specific role here. High-fiber foods require more chewing, which triggers more saliva and digestive secretions that physically fill your stomach. The bulk of fiber in the stomach directly increases the feeling of fullness. Practically, this means choosing whole grains over refined ones, eating whole fruit instead of drinking juice, and building meals around vegetables.
Prioritize Protein
Protein does double duty during a calorie deficit. First, it protects muscle mass. When your body is short on energy, it pulls from both fat and muscle tissue. Eating enough protein dramatically reduces how much muscle you lose. Guidelines for muscle preservation during weight loss recommend roughly 0.7 to 1.0 grams of protein per pound of body weight per day. For a 160-pound person, that’s 112 to 160 grams daily.
Second, protein burns more calories during digestion than any other macronutrient. Your body uses 15 to 30 percent of the calories from protein just to process it, compared to 5 to 10 percent for carbohydrates and 0 to 3 percent for fats. So 200 calories of chicken breast costs your body significantly more energy to digest than 200 calories of butter. This thermic effect won’t transform your results on its own, but it tilts the math slightly in your favor every time you eat.
Track, Then Adjust
Most people underestimate how much they eat by 20 to 50 percent. Tracking food intake, even temporarily, closes this gap. You don’t need to weigh every morsel forever, but two to four weeks of honest logging with a food scale and an app teaches you what portions actually look like. Many people discover that cooking oils, nuts, dressings, and beverages account for hundreds of unnoticed calories.
Weigh yourself at the same time each day (morning, after using the bathroom) and look at weekly averages rather than daily numbers. Water retention, sodium intake, hormonal cycles, and bowel habits can swing the scale by several pounds in a single day. If your weekly average isn’t trending downward after two to three weeks, your deficit is smaller than you think. Either reduce your intake by another 100 to 200 calories or add more movement.
The reverse is also worth watching. If you’re losing more than two pounds per week consistently, you’re likely cutting too aggressively, which increases muscle loss and makes the metabolic slowdown worse. A moderate, sustainable deficit protects your muscle, keeps hunger manageable, and gives you room to cut further later if progress stalls.