What it is, how to calculate it, and how to stay on track
Learn what a calorie deficit is, how to calculate yours, and how to track calories so you lose fat sustainably. Plus how big your deficit should be and how to use SpotWell to stay on target.
Track Calories with SpotWell →A calorie deficit means you eat fewer calories than your body burns over time. Your body then uses stored energy (mainly body fat) to make up the difference, so you lose weight. To lose fat, you need to be in a deficit; the size of that deficit affects how fast you lose and how sustainable it is.
First estimate how many calories you burn in a typical day (your TDEE—total daily energy expenditure). You can use a macro calculator or a TDEE formula based on your age, weight, height, and activity. Then subtract calories to create a deficit: a common target is 300–500 calories below TDEE for about 0.5–1 lb of fat loss per week. Larger deficits (e.g. 750–1000) can mean faster loss but are harder to sustain and can affect energy and muscle.
A moderate deficit of 300–500 calories per day is sustainable for most people and supports 0.5–1 lb of fat loss per week. Very aggressive deficits can lead to hunger, low energy, and muscle loss if protein and training aren’t prioritized. Start moderate, track your weight and how you feel, and adjust as needed. Use a calorie tracker or macro tracker to hit your target every day.
Tracking what you eat is the most reliable way to stay in a deficit. Weighing food and logging everything gives the best accuracy; for a simpler approach, use an app that lets you log quickly—for example, photo-based calorie tracking with SpotWell’s meal scanner so you can log meals in seconds and see calories and macros without manual search. The easier logging is, the more likely you’ll stay consistent and actually stay in your deficit.
While total calories drive fat loss, macros matter for hunger, energy, and preserving muscle. Keep protein high (e.g. 0.7–1 g per pound of body weight) when in a deficit; fill the rest with carbs and fats to your preference. Our macro calculator and what are macros guide can help you set targets. For more on losing fat while keeping muscle, see our how to lose weight without losing muscle and healthy fat loss guide.
| Deficit (per day) | Approx. fat loss per week | Sustainability | Best for |
|---|---|---|---|
| ~250 cal | ~0.25 lb | Very easy | Slow, minimal hunger |
| 300–500 cal | ~0.5–1 lb | Sustainable for most | Steady, maintainable loss |
| 500–750 cal | ~1–1.5 lb | Moderate; needs good nutrition | Faster loss with structure |
| 750–1000 cal | ~1.5–2 lb | Hard; risk of hunger and fatigue | Short-term only; consider guidance |
You’re in a deficit if you consistently eat fewer calories than you burn. Track your intake with a calorie or macro tracker and your weight over 2–4 weeks. If your weight is trending down (about 0.5–1 lb per week for a moderate deficit), you’re in a deficit.
A deficit of 300–500 calories per day below your TDEE is a good starting point for most people, leading to about 0.5–1 lb of fat loss per week. Use a macro or TDEE calculator to estimate your maintenance, then subtract 300–500 to set your target.
Some people lose weight by controlling portions, eating more whole foods, or using habits like intermittent fasting. For predictable results, tracking calories (or macros) is the most reliable. Apps like SpotWell make it fast with AI meal scanning so you don’t have to search for every food.
A moderate deficit with enough protein and resistance training usually preserves muscle. Very large deficits and low protein increase the risk of muscle loss. Aim for 0.7–1 g protein per pound of body weight and keep the deficit moderate (e.g. 300–500 cal below TDEE).
Use an app that lets you set a daily calorie (or macro) target and log meals easily. SpotWell’s AI meal scanner logs calories and macros from a photo so you can stay in your deficit without spending a lot of time on manual entry.
Download SpotWell today and start achieving your fitness and nutrition goals.