A daily calorie deficit of 500 calories is the most widely recommended starting point for steady weight loss, translating to roughly half a pound to one pound lost per week. But the right deficit for you depends on your current weight, activity level, and how much muscle you want to keep. Going too aggressive backfires more often than most people expect.
The 500-Calorie Starting Point
The classic rule of thumb is simple: cut about 500 calories per day from what your body actually burns, and you’ll lose somewhere between half a pound and a pound per week. This guideline comes from the older estimate that 3,500 calories equals roughly one pound of fat. In practice, weight loss isn’t quite that linear because your body adjusts along the way, but 500 calories per day remains a reliable and well-tested target for most people.
Some people do better with a smaller deficit of 250 to 300 calories, especially if they’re already relatively lean or have a history of losing and regaining weight. Others with more weight to lose can safely start closer to 750 calories below maintenance. The key is that your deficit is a percentage of what you personally burn each day, not a fixed number that works for everyone. A 500-calorie deficit is a much bigger deal for someone who burns 1,800 calories a day than for someone who burns 3,000.
Why Bigger Deficits Cost You Muscle
Cutting calories more aggressively doesn’t just speed up fat loss. It accelerates muscle loss, which is the opposite of what you want. A study comparing crash dieters eating 500 calories per day to moderate dieters eating 1,250 calories per day found that both groups lost the same amount of weight (about 19 pounds), but the crash dieters lost nearly three times as much muscle mass. That lost muscle lowers your metabolic rate, makes you look less toned, and sets the stage for regaining weight later.
This is why most guidelines set a floor: women should generally not go below 1,200 calories per day, and men should stay above 1,500 calories per day. Dropping below those thresholds puts you at risk for nutrient deficiencies and the cascade of symptoms that follow, including constant fatigue, poor concentration, weakened immunity, slow wound healing, feeling cold all the time, and low mood.
Your Body Fights Back
When you sustain a calorie deficit over weeks and months, your body doesn’t just passively burn through its reserves. It actively slows down to conserve energy, a process called metabolic adaptation. Research measuring this effect found that people in a sustained deficit burned 80 to 120 fewer calories per day than expected based on their weight loss alone. That gap isn’t accounted for by the weight they lost. It’s their body actively dialing down the thermostat.
This slowdown happens through several channels at once. Your thyroid hormones decrease, reducing your baseline metabolic rate. Leptin, the hormone that signals fullness, drops, making you hungrier. Your body temperature dips slightly. You also tend to move less throughout the day without realizing it, fidgeting less, taking fewer steps, and being less energetic during non-exercise activity. The larger your deficit, the harder your body pushes back.
How to Calculate Your Deficit
To figure out how many calories to eat, you first need to estimate your total daily energy expenditure (TDEE), which is everything your body burns in a day including exercise and basic functions like breathing and digestion. Online TDEE calculators use your age, weight, height, and activity level to generate an estimate. From there, you subtract your chosen deficit (typically 500 calories) to get your daily intake target.
Here’s the catch: these calculators aren’t very precise. Research on common estimation equations found typical errors of 150 to 400 calories per day, depending on the equation and the person. Even in the best-case scenarios, at least 20% of people get estimates that are off by more than 10%. Wearable fitness trackers aren’t much better for estimating calories burned, with errors ranging from about 13% to 30% depending on the device and activity. More than half the time, calculator-based calorie targets have errors exceeding 250 calories per day.
This doesn’t mean calculators are useless. It means you should treat your initial number as a starting estimate, not gospel. Use a calculator to set a target, follow it consistently for two to three weeks, and then adjust based on what actually happens on the scale. If you’re losing faster than a pound per week, you can eat a bit more. If you’re not losing at all, your estimate was probably too high.
Protecting Muscle While Losing Fat
The composition of the weight you lose matters as much as the number on the scale. Losing mostly fat while keeping your muscle requires two things beyond a moderate deficit: enough protein and some form of resistance training.
Current 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 170-pound person, that’s 119 to 170 grams of protein daily. This is significantly higher than what most people eat by default, so it usually requires deliberate planning. Spreading protein intake across meals rather than loading it into one or two sittings helps your body use it more efficiently for muscle repair.
Resistance training signals your body to hold onto muscle even when calories are low. Without it, your body has less reason to maintain metabolically expensive muscle tissue during a deficit, and it will break it down more readily for energy.
When Weight Loss Stalls
Plateaus are normal and expected. As you lose weight, your smaller body burns fewer calories at rest and during activity. The deficit that worked at 200 pounds won’t produce the same results at 180 pounds because your maintenance calories have dropped. When progress stalls for more than two to three weeks (and you’re confident you’re tracking accurately), you have two options: reduce your daily intake slightly or increase your physical activity. If you cut calories further, make sure you don’t dip below the 1,200/1,500 minimum floors.
One approach that helps manage both plateaus and the psychological grind of dieting is periodic diet breaks. Rather than dieting continuously for months, you lose about 1% of your body weight, then spend roughly a week eating at your new maintenance level before resuming the deficit. This pattern of intermittent restriction gives your hormones and hunger signals a partial reset, and research from the University of Sydney suggests it may help your body accept a lower baseline weight more readily than continuous dieting.
Choosing Your Target
For most people, a deficit between 300 and 500 calories per day hits the sweet spot: fast enough to see real progress on the scale, slow enough to preserve muscle and avoid the worst of metabolic adaptation. If you have a significant amount of weight to lose (50+ pounds), you can typically sustain a larger deficit early on because your body has more reserves to draw from. As you get leaner, a smaller deficit becomes more important to protect against muscle loss and hormonal disruption.
- Small deficit (250 to 300 calories): Best if you’re already fairly lean, prioritize muscle retention, or have struggled with adherence on stricter plans. Expect to lose about half a pound per week.
- Moderate deficit (400 to 500 calories): The standard recommendation for most people. Produces roughly half a pound to one pound of loss per week with manageable hunger.
- Aggressive deficit (600 to 750 calories): Reasonable for people with substantial weight to lose, but only sustainable for limited periods. Increases hunger, fatigue, and muscle loss risk the longer it’s maintained.
Whatever number you choose, consistency matters more than precision. A 400-calorie deficit you can sustain for four months will always outperform a 1,000-calorie deficit you abandon after three weeks.