Most people need to eat 500 to 750 fewer calories per day than their body burns to lose weight at a steady, sustainable pace. That translates to roughly 1 to 2 pounds of weight loss per week, which the CDC identifies as the rate most likely to stick long term. But the exact number depends on your size, age, sex, and activity level, so the real starting point is figuring out how many calories your body burns in the first place.
Finding Your Maintenance Calories
Your body burns calories constantly, not just during exercise but to breathe, digest food, pump blood, and maintain body temperature. The total number of calories you burn in a day is often called your total daily energy expenditure, or TDEE. A calorie deficit means eating less than that number so your body pulls the remaining energy it needs from stored fat.
The most widely used method for estimating TDEE starts with a formula called the Mifflin-St Jeor equation, which calculates your resting metabolic rate based on weight, height, age, and sex. For women, the formula is (10 × weight in kg) + (6.25 × height in cm) − (5 × age in years) − 161. For men, it’s the same but you add 5 instead of subtracting 161. That gives you the calories your body would burn doing absolutely nothing all day.
From there, you multiply by an activity factor to account for how much you move:
- Sedentary (desk job, little exercise): multiply by 1.2
- Lightly active (light exercise 1–3 days/week): multiply by 1.375
- Moderately active (moderate exercise 3–5 days/week): multiply by 1.55
- Active (hard exercise 6–7 days/week): multiply by 1.725
- Very active (intense daily training or physical job): multiply by 1.9
As an example, a 35-year-old woman who weighs 170 pounds (77 kg), is 5’6″ (168 cm), and exercises a few times a week would have a resting metabolic rate of about 1,418 calories. Multiplied by 1.375 for light activity, her estimated TDEE is roughly 1,950 calories. To create a 500-calorie daily deficit, she’d aim for about 1,450 calories per day.
How Large Your Deficit Should Be
A deficit of 500 calories per day is the most common recommendation because it produces about one pound of fat loss per week. Bumping that up to 750 calories per day gets closer to 1.5 pounds per week. Going beyond that is possible, but the tradeoffs get steep: more muscle loss, more hunger, and a higher likelihood of quitting.
Another way to think about it is as a percentage of your maintenance calories. A deficit of 15 to 25 percent tends to work well for most people. Someone maintaining at 2,400 calories, for instance, would aim for 1,800 to 2,040 calories per day. Percentage-based targets are useful because they naturally scale. A smaller person eating 1,800 calories to maintain their weight shouldn’t cut the same 750 calories as someone maintaining at 3,000.
There are also hard floors to keep in mind. Harvard Health recommends that women not go below 1,200 calories per day and men not go below 1,500 per day without medical supervision. Eating below those levels makes it very difficult to get adequate vitamins, minerals, and protein, and it raises the risk of gallstones, muscle loss, and other complications.
Diet, Exercise, or Both
You can create a calorie deficit by eating less, moving more, or combining the two. In practice, diet does the heavy lifting. As Mayo Clinic researchers have put it, you’d have to do huge amounts of physical activity to match what you can achieve by simply cutting calories from food. A 30-minute jog might burn 250 to 350 calories, while skipping a large sweetened coffee or a handful of cookies saves a similar amount with no time investment at all.
That said, exercise plays a different role than most people expect. It’s less effective for creating the initial deficit but significantly more effective for keeping weight off afterward. The best approach for most people is to get the majority of the deficit from dietary changes and use exercise to preserve muscle, improve energy, and protect against regain. Even modest movement, like walking 20 to 30 minutes most days, adds up over weeks and months.
Why Your Deficit Shrinks Over Time
One of the most frustrating parts of a calorie deficit is that your body fights back. When you eat less than you burn, your metabolism doesn’t stay fixed. It slows down by more than you’d expect from the weight you’ve lost alone, a process researchers call adaptive thermogenesis. This can kick in within the first week of dieting. One study found that resting energy expenditure dropped by an average of 178 calories per day after just one week of calorie restriction, independent of any change in body size.
That means the deficit you calculated at the start quietly narrows as you go. Someone who started with a 500-calorie deficit may only be in a 300-calorie deficit a few weeks later, even if they haven’t changed what they eat. This is a major reason weight loss stalls. The fix isn’t to slash calories further, which just accelerates the metabolic slowdown. Instead, it helps to recalculate your TDEE every few weeks as your weight drops, incorporate resistance training to preserve the muscle tissue that keeps your metabolism higher, and accept that the rate of loss will naturally slow over time.
The same study found that people whose metabolisms adapted the most aggressively in the first week lost about 2 kg (roughly 4.4 pounds) less over six weeks compared to those with milder adaptation. Individual variation is real. Two people eating the same deficit won’t always get the same results, and that’s largely biology, not willpower.
Putting It Into Practice
Start by estimating your TDEE using the formula or an online calculator based on the Mifflin-St Jeor equation. Subtract 500 calories as your starting target. Track what you eat for one to two weeks, then check the scale. If you’re losing about a pound a week, you’ve found the right range. If nothing is moving, your TDEE estimate may have been too high, or you may be underestimating portions.
A food scale and a simple tracking app are more accurate than eyeballing, especially early on. Most people underestimate their calorie intake by 20 to 50 percent, which is enough to erase a moderate deficit entirely. You don’t need to track forever, but a few weeks of honest measurement can recalibrate your sense of portion sizes.
Keep protein intake relatively high, around 25 to 30 percent of your calories. Protein helps preserve muscle during a deficit, keeps you fuller for longer, and has a higher thermic effect, meaning your body burns more calories digesting it compared to carbs or fat. Prioritize whole foods that are naturally filling: vegetables, lean proteins, legumes, and whole grains tend to provide more volume and satiety per calorie than processed alternatives.
Finally, think in weeks and months rather than days. A single day over your target doesn’t erase a week of consistency. Weight fluctuates by 2 to 5 pounds daily based on water, sodium, and digestion alone. The trend over two to four weeks tells you whether your deficit is working. If the overall direction is downward, you’re on track.