Most women need to eat between 1,400 and 1,800 calories per day to lose weight at a steady, sustainable pace, though your specific number depends on your age, height, current weight, and how active you are. The general principle is straightforward: you need to eat fewer calories than your body burns. A deficit of about 500 calories per day leads to roughly one pound of weight loss per week, which the CDC identifies as the sweet spot for keeping weight off long-term (1 to 2 pounds per week).
How to Estimate Your Personal Number
Your body burns a baseline number of calories just to keep you alive: breathing, circulating blood, regulating temperature. This is your resting metabolic rate. The most widely used formula for estimating it in women is the Mifflin-St Jeor equation, which accounts for your weight, height, and age. But that baseline only tells you what your body burns at complete rest. To get the full picture, you multiply by an activity factor that reflects how much you move during the day.
Here’s what those activity multipliers look like in practice:
- Sedentary (desk job, little exercise): multiply by 1.25
- Moderately active (exercise 3 to 5 days a week): multiply by 1.75
- Very active (intense daily exercise or physical job): multiply by 2.2
The result is your total daily energy expenditure, or the number of calories you burn in a full day. To lose about one pound per week, subtract 500 from that number. To lose closer to two pounds per week, subtract 1,000, though this often drops calorie intake uncomfortably low and is harder to maintain.
What This Looks Like for Different Women
A 35-year-old woman who is 5’5″, weighs 170 pounds, and works a desk job burns roughly 1,750 calories per day. Subtracting 500 puts her weight loss target around 1,250 calories, which is on the low side and may feel restrictive. Adding three to four days of moderate exercise bumps her total burn closer to 2,100, making a 1,600-calorie diet both effective and more livable.
A 28-year-old woman who is 5’7″, weighs 200 pounds, and exercises regularly might burn around 2,400 calories per day. A 500-calorie deficit gives her a comfortable 1,900 calories to work with, enough to include satisfying meals without constant hunger. This is why activity level matters so much: it determines not just how fast you lose weight, but how pleasant the process feels.
Nutritional guidelines generally recommend that women not drop below 1,200 calories per day without medical supervision, because it becomes difficult to get adequate vitamins, minerals, and protein at that level.
Why Age Changes the Equation
Your metabolism slows gradually with age, partly because you lose muscle mass and partly because of hormonal shifts. The most dramatic change happens around menopause. During perimenopause and menopause, declining hormone levels can reduce your resting metabolic rate by 250 to 300 calories per day. That’s the equivalent of a full snack or small meal disappearing from your daily budget without any change in what you eat.
This means a calorie intake that maintained your weight at 40 can cause slow, steady weight gain by 52. Women in this stage often need to either eat less, move more, or ideally both to compensate. Strength training becomes especially valuable here because it helps preserve the muscle tissue that keeps your metabolism higher.
Your Body Fights Back Against Calorie Deficits
One of the most important things to understand about calorie restriction is that your body adapts to it. When you eat less for an extended period, your metabolism slows beyond what the loss of body weight alone would explain. Researchers call this metabolic adaptation, and it’s a real, measurable phenomenon.
A well-known NIH study followed contestants from The Biggest Loser over six years. At the end of the initial 30-week competition, their metabolisms had slowed by about 275 calories per day more than expected based on their new body size. Six years later, that gap had actually widened to nearly 500 calories per day, even among those who had regained significant weight. The participants who lost the most weight experienced the greatest metabolic slowing.
This doesn’t mean weight loss is futile. It means that aggressive, rapid calorie cutting tends to provoke a stronger metabolic pushback than gradual, moderate approaches. Losing one to two pounds per week, rather than five or six, gives your body less reason to slam the brakes on your metabolism. It also explains why the number you calculated at the start of your weight loss journey may need to be recalculated every 10 to 15 pounds lost.
Making a Calorie Deficit Feel Sustainable
The number of calories you eat matters, but so does what fills those calories. Protein is the most filling macronutrient per calorie, so anchoring meals around lean protein sources (chicken, fish, eggs, legumes, Greek yogurt) helps control hunger without eating more. Fiber-rich foods like vegetables, whole grains, and beans add bulk to meals, making your plate look and feel more substantial. While research on fiber and appetite is mixed (only about 39% of fiber interventions significantly reduced appetite ratings in a systematic review), the volume that high-fiber foods add to meals has practical benefits that go beyond any single nutrient.
Spreading your calories across three meals and one or two snacks, rather than saving everything for one large meal, helps keep blood sugar stable and prevents the kind of ravenous hunger that leads to overeating. Drinking water before meals also helps, since thirst is easily mistaken for hunger.
The most effective calorie target is one you can actually maintain for months, not one that produces the fastest results for two weeks before you abandon it. If your calculated deficit feels miserable, reduce it. A 300-calorie daily deficit still produces meaningful weight loss over time, roughly two and a half pounds per month, and you’re far more likely to stick with it.
When to Recalculate
Your calorie needs aren’t static. As you lose weight, your body requires fewer calories both because there’s less tissue to fuel and because of the metabolic adaptation described above. A good rule of thumb is to recalculate after every 10 to 15 pounds of weight loss, or whenever your progress stalls for more than two to three weeks despite consistent eating and exercise habits. At that point, you can either modestly reduce calories, increase physical activity, or both to restore the deficit your body has closed.
Plateaus are normal and expected. They don’t mean something is wrong. They mean your body has caught up to your current routine, and a small adjustment is needed to keep moving forward.