Your calorie deficit is the gap between the calories your body burns each day and the calories you eat. For most people, a deficit of about 500 calories per day produces roughly one pound of weight loss per week, while a 1,000-calorie daily deficit can push that closer to two pounds. The exact number depends on your size, age, sex, and activity level.
How to Calculate Your Maintenance Calories
Before you can figure out your deficit, you need a starting point: the number of calories your body burns in a typical day. This is often called your maintenance level or total daily energy expenditure (TDEE). It has two main components: the calories your body burns just to keep you alive (breathing, digesting, pumping blood) and the calories you burn through movement and exercise.
The most widely recommended formula for estimating that baseline burn is the Mifflin-St Jeor equation. It uses your weight in kilograms, height in centimeters, and age in years:
- Women: (10 × weight) + (6.25 × height) – (5 × age) – 161
- Men: (10 × weight) + (6.25 × height) – (5 × age) + 5
This gives you your basal metabolic rate, the calories you’d burn lying in bed all day. To get your actual daily burn, you multiply by an activity factor: 1.2 if you’re mostly sedentary, 1.375 for light exercise a few days a week, 1.55 for moderate exercise most days, and 1.725 if you’re very active. A 35-year-old woman who weighs 170 pounds (77 kg), stands 5’5″ (165 cm), and exercises lightly would have a basal rate of around 1,390 calories and a maintenance level of roughly 1,910 calories per day. Her 500-calorie deficit target would be about 1,410 calories daily.
How Big Should Your Deficit Be
A 500-calorie daily deficit is the most common recommendation because it’s large enough to produce visible results but small enough to sustain for months. A 1,000-calorie deficit is considered the upper end of what’s safe without medical supervision, and it’s significantly harder to stick with long-term.
There are hard floors you shouldn’t drop below. Women should not eat fewer than 1,200 calories per day and men should not go below 1,500 calories per day without personalized guidance from a doctor or dietitian. If subtracting 500 or 1,000 calories from your maintenance number puts you under those thresholds, your deficit needs to be smaller, or you need to add exercise to widen the gap from the other side.
For people with more weight to lose, a larger deficit is generally tolerable because the body has more stored energy to draw from. If you’re already lean, a smaller, more conservative deficit (250 to 500 calories) helps you avoid losing muscle along with fat.
Why the “3,500 Calories Per Pound” Rule Is Imperfect
You’ll see the old guideline everywhere: cut 3,500 calories and lose one pound of fat. The Mayo Clinic notes that while roughly 3,500 calories of energy does equal about one pound of fat, the neat math of “500 fewer calories per day equals one pound per week” doesn’t hold true for everyone. Your body isn’t a simple calculator. As you lose weight, you burn fewer calories at rest, and your body actively resists the deficit through a process called metabolic adaptation.
Research on this adaptation is striking. In one study published in The American Journal of Clinical Nutrition, men placed on a 50% calorie restriction saw their resting energy expenditure drop by about 266 calories per day, and nearly half of that drop (108 calories per day) was the body deliberately slowing its engine beyond what the weight loss alone would explain. This slowdown kicked in within just three days of starting the restriction and was linked to drops in insulin secretion and shifts in fluid balance.
What this means in practice: a 500-calorie deficit that works perfectly in week one will produce slightly less fat loss by week six, and noticeably less by month three. This is normal and not a reason to slash calories further. It’s the main reason weight loss slows over time even when you’re doing everything right.
Protecting Muscle During a Deficit
When you eat fewer calories than you burn, your body pulls energy from both fat stores and muscle tissue. Losing muscle slows your metabolism further and makes it harder to keep weight off later. Two strategies minimize this.
First, eat enough protein. Research on athletes cutting weight suggests 1.6 to 2.4 grams of protein per kilogram of body weight per day during a calorie deficit. For a 170-pound person, that’s roughly 123 to 185 grams of protein daily. Going above 2.4 grams per kilogram doesn’t appear to offer additional muscle-sparing benefits. You don’t need to be an athlete for this to apply. Anyone in a calorie deficit benefits from keeping protein high relative to their other food choices.
Second, do some form of resistance training. Lifting weights, bodyweight exercises, or resistance bands all signal your body to preserve muscle. Without that signal, your body has less reason to keep metabolically expensive muscle tissue when energy is scarce. Even two to three sessions per week makes a measurable difference.
Setting Realistic Expectations
The first week or two of a calorie deficit often produces a dramatic drop on the scale, sometimes three to five pounds. Most of that is water and stored carbohydrate, not fat. After that initial flush, expect roughly 0.5 to 1 pound per week with a 500-calorie deficit, or up to 2 pounds per week with a 1,000-calorie deficit. Some weeks the scale won’t budge at all, especially if you’re retaining water from a salty meal, a hard workout, or hormonal fluctuations.
Weight loss isn’t linear. A more reliable way to track progress is to weigh yourself daily, then compare weekly averages. If your average is trending downward over two to three weeks, your deficit is working regardless of what any single morning weigh-in shows.
Adjusting Your Deficit Over Time
The deficit that works at 200 pounds won’t produce the same results at 170 pounds because a smaller body burns fewer calories. Every 10 to 15 pounds of weight loss, it’s worth recalculating your maintenance number and resetting your target intake. If you started at a 500-calorie deficit and hit a genuine plateau (not just a week of stalling, but three to four weeks of no change in your weekly averages), you have two options: reduce your intake by another 100 to 200 calories, or add more physical activity to increase the burn side of the equation.
Adding movement is often the better choice late in a diet because your calorie intake may already be close to those safety minimums. A 30-minute brisk walk burns roughly 150 to 200 calories for most people, which can restore a meaningful deficit without cutting more food. The combination of a moderate calorie reduction and regular activity is consistently more sustainable than deep calorie restriction alone.