Most people need to eat roughly 500 calories below their maintenance level to lose weight at a steady, sustainable pace. That typically lands somewhere between 1,200 and 1,800 calories per day for most adults, though your exact number depends on your size, age, sex, and how active you are. The real starting point isn’t a universal calorie target. It’s figuring out how many calories your body burns in a day, then subtracting from there.
Find Your Maintenance Calories First
Before you can set a deficit, you need to know your baseline: the number of calories your body uses just to get through a normal day. This is called your total daily energy expenditure, or TDEE. It accounts for everything from breathing and digestion to walking, exercising, and fidgeting.
The most widely used method for estimating this is 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) − 161. For men, it’s the same but you add 5 instead of subtracting 161. That gives you a resting number, which you then multiply by an activity factor:
- 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 a quick example: a 35-year-old woman who weighs 170 pounds (77 kg), stands 5’5″ (165 cm), and exercises a few times a week would have a resting rate of about 1,434 calories. Multiply that by 1.55 for moderate activity, and her maintenance calories come out to roughly 2,223 per day. Her deficit target would start around 1,723 calories.
How Big Your Deficit Should Be
A daily deficit of 500 calories is the most common recommendation because it produces roughly one pound of weight loss per week for most people. The CDC notes that losing 1 to 2 pounds per week is the pace most likely to lead to lasting results. A 500-calorie deficit sits at the lower, more manageable end of that range.
You may have heard the old rule that 3,500 calories equals one pound of fat, making a 500-calorie daily deficit equal to exactly one pound per week. That math is overly simple. When you lose weight, you lose a mix of fat, lean tissue, and water, not pure fat. Your body also adapts to eating less over time, so the rate of loss slows. The 500-calorie starting point is still useful as a guideline, but don’t expect perfectly linear results on the scale.
If you have more weight to lose, a deficit of 750 or even 1,000 calories per day can be appropriate, bringing you closer to two pounds of loss per week. But there’s a floor you shouldn’t go below. Diets under 800 calories a day are classified as very low calorie and carry real risks: up to 25% of people on these plans develop gallstones, and without medical supervision, they can cause a loss of more than 25% of lean body mass. For most people, staying above 1,200 calories (women) or 1,500 calories (men) provides enough nutrition to function well.
Why Your Deficit Stops Working Over Time
Your body doesn’t passively accept an energy shortage. Within the first week of cutting calories, your metabolism begins to slow in a process researchers call adaptive thermogenesis. One study measured this drop at an average of about 178 calories per day, meaning your body quietly burns less energy than the math would predict. This slowdown happens through changes in hormone signaling, including shifts in thyroid function and the hormones that regulate hunger and fat storage.
This is why people often hit a plateau after several weeks of steady progress. The deficit you started with has effectively shrunk because your body is now spending less energy. The practical fix is straightforward: reassess your calorie target every few weeks. As you lose weight, your maintenance calories drop (a smaller body burns fewer calories), and the metabolic adaptation chips away at your deficit further. Recalculating every 10 to 15 pounds lost keeps things on track.
Protecting Muscle While Losing Fat
The calories you eat matter, but so does what those calories are made of. Protein is the single most important factor in preserving muscle during a deficit. Guidelines for muscle maintenance during weight loss recommend roughly 0.7 to 1.0 grams of protein per pound of body weight per day. For a 170-pound person, that’s 119 to 170 grams of protein daily.
That’s a meaningful amount. It means protein needs to anchor most of your meals and snacks, not just show up once at dinner. Chicken, fish, eggs, Greek yogurt, legumes, and protein-rich grains like quinoa all contribute. Hitting this target matters because when your body is running on fewer calories than it needs, it will pull energy from both fat and muscle. Adequate protein, combined with some form of resistance exercise, signals your body to hold onto muscle and preferentially burn fat.
Signs Your Deficit Is Too Aggressive
Cutting calories is supposed to feel slightly uncomfortable, not miserable. There’s a clear line between a productive deficit and one that’s doing more harm than good. When your body interprets a large deficit as starvation, it slows your metabolism as a protective response, which ironically makes further weight loss harder.
Physical warning signs of an overly aggressive deficit include persistent fatigue and weakness, hair loss, constipation, feeling cold all the time, and difficulty concentrating. More serious consequences include electrolyte imbalances, abnormal heart rhythms, low blood sugar, and dehydration. If you’re losing more than two pounds per week consistently (outside of the first week or two, when water weight drops quickly), your deficit is likely too large.
Putting Your Numbers Together
Here’s the practical sequence: calculate your maintenance calories using the formula and activity multiplier above, then subtract 500 calories for a moderate deficit or up to 750 for a more aggressive but still safe approach. That’s your daily calorie target. Make sure at least 25 to 35% of those calories come from protein to preserve muscle. Weigh yourself weekly under consistent conditions (same time of day, same clothing) and look at the trend over two to three weeks rather than day-to-day fluctuations.
If the scale isn’t moving after three weeks, your actual maintenance calories are likely lower than the formula predicted, which is common. Drop your target by another 100 to 150 calories and reassess. If you’re losing faster than two pounds per week, add calories back. The goal is a pace you can sustain for months, not a sprint that burns out in weeks.