Eating in a calorie deficit means consuming fewer calories than your body burns each day, and it’s the only reliable way to lose body fat. A deficit of 500 to 750 calories per day is the range recommended by most obesity guidelines, which typically produces about one to one and a half pounds of weight loss per week. The mechanics are straightforward, but doing it consistently without feeling miserable or losing muscle takes some strategy.
Finding Your Calorie Target
Before you can eat below your needs, you need a reasonable estimate of what your body actually burns. The most widely used method starts with your basal metabolic rate, the calories your body uses just to keep you alive at rest. The Mifflin-St Jeor equation is the standard formula:
- For women: (10 × weight in kg) + (6.25 × height in cm) − (5 × age) − 161
- For men: (10 × weight in kg) + (6.25 × height in cm) − (5 × age) + 5
That gives you resting calories. You then multiply by an activity factor: 1.2 if you’re mostly sedentary, 1.375 if you’re lightly active, 1.55 for moderate activity, and up to 1.9 if you’re very active. The result is your total daily energy expenditure, or TDEE. Subtract 500 to 750 from that number and you have your daily calorie target.
For example, a moderately active 35-year-old woman who weighs 75 kg (about 165 pounds) and stands 165 cm (5’5″) would have a TDEE around 2,200 calories. A 500-calorie deficit puts her target at roughly 1,700 per day. That’s a realistic, sustainable number. Most women shouldn’t go below 1,200 calories and most men shouldn’t drop below 1,500 without medical supervision, because dipping under those floors increases the risk of nutrient deficiencies, fatigue, and muscle loss.
What to Actually Put on Your Plate
A calorie deficit doesn’t dictate what you eat, but your food choices determine whether you feel satisfied or constantly hungry. The most useful concept here is energy density: how many calories a food packs into a given volume. Foods with high water and fiber content let you eat large, filling portions without blowing your calorie budget.
The contrast can be dramatic. A cup of grapes has about 104 calories. A cup of raisins, which is the same fruit with the water removed, has 480. Half a grapefruit is 90% water and comes in at just 64 calories. Air-popped popcorn delivers a full cup for about 30 calories. Building meals around vegetables like broccoli, zucchini, tomatoes, carrots, and salad greens gives you physical volume in your stomach for very few calories.
A practical plate in a calorie deficit looks something like this: fill half with vegetables or salad, a quarter with a protein source, and a quarter with a starchy carb or whole grain. This isn’t a rigid rule, but it naturally keeps energy density low while covering your nutritional bases. You can still eat foods you enjoy, including higher-calorie ones. The key is that the bulk of your meals comes from foods that fill space in your stomach without filling your calorie budget.
Prioritize Protein
Protein is the single most important nutrient when you’re eating below maintenance. It protects your muscle mass, keeps you fuller for longer, and has a higher thermic effect than carbs or fat, meaning your body burns more calories just digesting it. Without enough protein, a significant portion of the weight you lose will come from muscle rather than fat.
Research on athletes maintaining a calorie deficit suggests a range of 1.6 to 2.4 grams of protein per kilogram of body weight per day. Resistance-trained individuals may need even more, up to 2.7 grams per kilogram. For a 75 kg person, that translates to roughly 120 to 180 grams of protein daily. Even if you’re not an athlete, aiming for the lower end of that range (around 1.6 g/kg) is a solid target for preserving muscle.
In practical terms, this means including a protein source at every meal. Chicken breast, fish, Greek yogurt, eggs, cottage cheese, lentils, and tofu are all relatively high in protein for their calorie cost. If you find it hard to hit your target through food alone, a protein shake can close the gap without adding much volume to your day.
Eat More Fiber
Fiber slows digestion, which means food sits in your stomach longer and you stay satisfied between meals. High-fiber foods also tend to require more chewing, which itself signals fullness to your brain. A study published in the Annals of Internal Medicine found that people who simply aimed to eat 30 grams of fiber per day lost weight and improved blood pressure and insulin sensitivity, even without following any other dietary rules.
Thirty grams is a good daily target. Most people fall well short of it. You can get there by eating vegetables at every meal, choosing whole grains over refined ones, snacking on fruit, and including beans or lentils a few times per week. A cup of cooked lentils alone provides about 15 grams.
Why Tracking Matters (and Where It Goes Wrong)
Most people who believe they’re eating in a deficit but aren’t losing weight are simply eating more than they think. A well-known study at a metabolic research unit found that people who described themselves as “diet resistant” underreported their actual food intake by an average of 47% and overestimated their physical activity by 51%. Their metabolisms were completely normal. The gap was entirely in perception.
This doesn’t mean you need to weigh every gram of food forever, but it does mean that eyeballing portions is unreliable, especially early on. Using a food scale and a tracking app for even a few weeks can recalibrate your sense of what portions actually contain. Pay attention to cooking oils, sauces, nuts, and liquid calories. These are the most common sources of untracked calories because they’re calorie-dense and easy to underestimate.
Once you develop an intuitive sense of portion sizes and calorie costs for the foods you regularly eat, you can step back from meticulous tracking and rely on habits and general awareness instead.
Your Body Will Push Back
After you’ve been in a deficit for a while, your body adapts in ways that make continued weight loss harder. Maintaining a 10% or greater reduction in body weight triggers roughly a 20 to 25% drop in daily energy expenditure. About 10 to 15% of that drop can’t be explained by the fact that you weigh less. It’s your body actively conserving energy.
Several things happen at once. Your thyroid produces less of its active hormone, which slows your metabolism. Your nervous system dials down its activity, reducing the calories you burn through fidgeting, posture maintenance, and other unconscious movements. Your muscles become more efficient, burning fewer calories to do the same work. And leptin, a hormone released by fat cells, drops as you lose fat. Lower leptin signals your brain that energy stores are depleted, which ramps up hunger and reduces your motivation to move.
This is not a sign that something is broken. It’s a predictable biological response to sustained weight loss. But it means the deficit that worked in month one may no longer produce results in month four. You have a few options when this happens: slightly reduce your calorie intake, increase your activity level, or take a planned diet break where you eat at maintenance for one to two weeks before resuming. Diet breaks can help normalize some of these hormonal signals and make the deficit more tolerable when you return to it.
Practical Habits That Make It Sustainable
The deficit itself is simple math. The hard part is living in it day after day without it taking over your life. A few strategies make this dramatically easier.
Cook more meals at home. Restaurant food is notoriously difficult to estimate because of hidden oils, butter, and large portions. You don’t need to avoid eating out entirely, but the more meals you prepare yourself, the more control and accuracy you have. Batch cooking on weekends can save time during the week and reduce the temptation to order takeout when you’re tired.
Front-load your protein and fiber. If your first meal of the day is high in both, you’ll typically feel less hungry through the afternoon and make better choices at dinner. Eggs with vegetables, Greek yogurt with fruit, or a bean-heavy scramble all work well for this.
Don’t drink your calories unless it’s a protein shake serving a specific purpose. Juice, soda, sweetened coffee drinks, and alcohol add calories without filling you up at all. Swapping these for water, sparkling water, or black coffee can free up a surprising number of calories for actual food.
Finally, expect imperfect days. A single meal over your target doesn’t erase a week of progress. Weight loss happens over weeks and months, not hours. The people who succeed long-term are the ones who return to their plan after a slip rather than abandoning it entirely.