Eating at a calorie deficit means consuming fewer calories than your body burns each day, and it’s the fundamental requirement for losing weight. A deficit of roughly 500 calories per day translates to about one pound of fat loss per week. The process is straightforward in concept, but doing it sustainably takes some planning around how much to eat, what to eat, and how to track your progress without making yourself miserable.
Find Your Starting Number
Before you can eat below your maintenance calories, you need a reasonable estimate of what maintenance actually is. Your total daily energy expenditure has two main components: your resting metabolic rate (the calories your body burns just keeping you alive) and the calories burned through movement, from formal exercise to fidgeting and walking around your kitchen.
Several factors influence your resting metabolic rate that you can’t change: age, biological sex, height, and genetics. Men burn more at rest than women. Taller people burn more than shorter people at the same weight. Your metabolic rate naturally declines as you get older. But one major factor you can influence is your amount of lean muscle tissue. People with more muscle burn more calories at rest, which is one reason strength training matters during a deficit.
The simplest way to estimate your number is a calorie tracking app. These use prediction equations that factor in your age, sex, height, weight, and activity level to generate a starting target. No equation is perfectly accurate for every person, so treat it as a starting point you’ll adjust based on real results over two to three weeks. If you’re losing weight at the rate you expected, the estimate was close enough. If nothing’s changing, your actual expenditure is likely lower than the estimate.
Choose the Right Size Deficit
The CDC recommends a weight loss pace of one to two pounds per week as the range most likely to stick long term. For most people, that means a daily deficit of 500 to 1,000 calories below maintenance. A 500-calorie deficit is a good default starting point: it’s large enough to produce visible progress but small enough that you won’t feel like you’re starving.
Bigger deficits produce faster results on paper, but they come with real tradeoffs. Your body responds to large calorie cuts by reducing something called non-exercise activity thermogenesis, which is all the movement you do without thinking about it: pacing while on the phone, taking the stairs, shifting in your chair. Research published in the American Journal of Physiology found that during severe energy restriction (around 800 calories per day), drops in this unconscious movement accounted for 33% of the total decrease in daily energy expenditure in lean subjects and up to 51% in obese subjects who had lost 20% of their body weight. In other words, the harder you cut, the more your body quietly dials down its calorie burn to compensate.
Very low calorie intake also directly suppresses your resting metabolic rate. Your body becomes more “energy efficient” as a survival mechanism, which means the math that worked in week one stops working by week six. A moderate deficit avoids triggering this response as aggressively, keeping your progress more predictable over months.
Prioritize Protein
When you eat fewer calories than you burn, your body pulls energy from both fat stores and muscle tissue. The single most effective way to tip that ratio toward fat loss and away from muscle loss is eating enough protein. Research on athletes maintaining a calorie deficit found that 1.6 to 2.4 grams of protein per kilogram of body weight per day was the range needed to preserve lean mass. For a 170-pound person, that works out to roughly 125 to 185 grams of protein daily.
You don’t need to be an athlete for this to matter. Losing muscle during a deficit lowers your resting metabolic rate, which means you’ll burn fewer calories at rest going forward, making it harder to keep losing weight and easier to regain it. Protein also happens to be the most satiating macronutrient. Gram for gram, it keeps you feeling full longer than carbohydrates or fat, which makes the whole process of eating less feel considerably easier.
Practical sources include chicken breast, Greek yogurt, eggs, fish, cottage cheese, tofu, and legumes. Spreading your protein across three or four meals rather than loading it into one tends to be more effective for muscle retention and keeps hunger more stable throughout the day.
Eat More Food for Fewer Calories
One of the most common reasons people abandon a calorie deficit is hunger, and the fix isn’t willpower. It’s choosing foods that take up a lot of space in your stomach without packing many calories. This concept, sometimes called volumetric eating, is built around calorie density: the number of calories per gram of food.
Fat contains 9 calories per gram, while protein and carbohydrates each contain 4 calories per gram. But the real game-changer is water and fiber content. Foods with high water content have an extremely low calorie density, often under 0.6 calories per gram. The Cleveland Clinic identifies several categories that fit this profile:
- Fruits: bananas, apples, grapefruit, berries, melon
- Non-starchy vegetables: broccoli, carrots, beets, Brussels sprouts, spinach, zucchini
- Broth-based soups: nearly any variety
- Nonfat or low-fat dairy: nonfat yogurt, skim milk, or unsweetened milk alternatives
Building meals around these foods means your plate looks full and your stomach feels full, even though the calorie count is moderate. A practical approach: fill half your plate with vegetables, a quarter with a protein source, and a quarter with a starch or grain. This isn’t a rigid rule, but it naturally keeps meals in the 400 to 600 calorie range without requiring you to weigh every ingredient.
Track Accurately or Don’t Bother
Calorie tracking only works if it reflects what you’re actually eating. Most people significantly underestimate their intake when they eyeball portions. A tablespoon of olive oil is 120 calories, and the difference between a measured tablespoon and what you pour freely into a pan can easily be double or triple that.
A digital kitchen scale is the single most useful tool for accurate tracking. Weighing food in grams removes the guesswork that comes with volume measurements like cups and tablespoons, where packing density varies wildly. A “cup” of rice can differ by 50 or more calories depending on how tightly it’s packed. Image-based estimation methods, even those using technology, still carry calorie errors in the range of 6 to 12%, and human estimation without any tools is far worse.
You don’t need to weigh every meal forever. Most people eat a relatively small rotation of meals. Weigh and log your common meals for a few weeks until you can reliably eyeball your usual portions. After that, you can scale back to periodic check-ins when progress stalls or your routine changes.
Handle Plateaus and Adjustments
Weight loss is not linear. You will have weeks where the scale doesn’t move despite doing everything right, usually because of water retention from sodium, hormonal shifts, or simply having more food in your digestive tract. Judging progress over two to three week windows rather than day to day filters out this noise.
True plateaus, where your weight hasn’t budged in three or more weeks, usually mean your energy expenditure has decreased. This happens naturally as you lose weight: a smaller body burns fewer calories. It also happens because of the metabolic adaptation described earlier, where your body reduces unconscious movement and becomes more efficient. At this point, you have two options: reduce your calorie intake by another 100 to 200 calories per day, or increase your activity level. Adding a daily 20-minute walk is often enough to break a plateau without further cutting food.
What a Deficit Day Looks Like
Suppose your estimated maintenance is 2,200 calories and you’re targeting a 500-calorie deficit, putting your daily goal at 1,700 calories. A realistic day might look like this: a breakfast of eggs with vegetables and toast (around 400 calories), a lunch of grilled chicken over a large salad with olive oil dressing (around 500 calories), an afternoon snack of Greek yogurt with berries (around 150 calories), and a dinner of salmon with roasted broccoli and rice (around 550 calories). That leaves about 100 calories of margin for a small snack, cooking oils, or a splash of cream in your coffee.
Notice that none of those meals are tiny. The deficit comes from choosing foods that are filling relative to their calorie content and being deliberate about cooking fats and sauces, which is where untracked calories most often hide. You don’t need to eliminate any food group, skip meals, or avoid eating after a certain hour. The deficit itself is what drives fat loss, not the specific timing or food choices, though both can make the process feel easier or harder depending on your preferences.
Strength Training Protects Your Progress
A calorie deficit tells your body to pull energy from its reserves. Without a signal to keep muscle, your body will break down both fat and lean tissue. Resistance training, even two to three sessions per week, provides that signal. Combined with adequate protein, it shifts the ratio heavily toward fat loss while preserving the muscle that keeps your metabolism higher.
This matters beyond aesthetics. People who lose weight through diet alone lose a higher percentage of muscle, which lowers their resting metabolic rate more than necessary and sets them up for faster regain. People who include resistance training maintain more muscle, burn more calories at rest, and typically find it easier to maintain their new weight once they transition out of a deficit.