What Is a Calorie Deficit? How It Works for Weight Loss

Quick answer: What is a calorie deficit? It happens when you eat fewer calories than your body burns in a day. To cover the shortfall, your body turns to stored fat for energy, which is what causes weight loss. A daily deficit of about 500 calories leads to roughly 1 pound of fat loss per week for most people.

Key takeaways

• A calorie deficit means eating fewer calories than your body burns, and the shortfall comes mostly from stored fat.
• A daily deficit of 300 to 500 calories is the sustainable range for most people, about 0.5 to 1 lb per week.
• Diet does most of the work, but strength training protects muscle while fat comes off.
• Track for two honest weeks before deciding the deficit is not working, and recalculate every 4 to 6 weeks.
• Talk to a doctor first if you are pregnant, breastfeeding, underweight, have diabetes or an eating disorder history, or take daily medication.

What is a calorie deficit?

A calorie deficit simply means calories in are lower than calories out. Every day your body burns a certain number of calories to keep you alive, digest food, and fuel everything you do. When you eat less than that number, the gap is your calorie deficit, and your body fills it by breaking down stored energy, mostly body fat. You can skip the manual math with our free calorie deficit calculator.

Think of it like a bank account. Your daily calorie burn is your spending, and the food you eat is your income. Spend more than you earn and the difference comes out of savings. In this case, the savings account is your body fat.

The opposite is a calorie surplus (eating more than you burn, which leads to weight gain), and eating exactly what you burn is called eating at maintenance.

The scientific name for this balance is energy balance. When intake matches expenditure, you are in energy balance and weight stays steady. When intake falls below expenditure, you are in negative energy balance, which is the formal term for a calorie deficit. The reverse, eating more than you burn, is positive energy balance. Knowing the term helps because research papers and calculators use it instead of the everyday phrase.

How Many Calories Does Your Body Burn?

Your total daily burn has a name: TDEE (Total Daily Energy Expenditure). It has three parts:

Component	Share of daily burn	What it is
BMR (basal metabolic rate)	60 to 70%	Calories burned just staying alive: breathing, circulation, brain function
TEF (thermic effect of food)	About 8 to 15%	Calories burned digesting what you eat (protein costs the most to digest)
Activity	15 to 30%	Everything else: exercise, walking, fidgeting, housework

Your calorie deficit is measured against your TDEE. If your TDEE is 2,200 calories and you eat 1,700, your deficit is 500. You can calculate your TDEE here in under a minute.

A note on terms: you will also see resting energy expenditure, or REE, used where this article says BMR. The two are close but not identical. BMR is measured under strict conditions, shortly after waking and after at least 12 hours without food. REE is measured under looser conditions, a few hours after a meal, and usually runs slightly higher. In practice the two differ by no more than about 10 percent, and most calculators and articles use them interchangeably. The Mifflin-St Jeor equation in this guide estimates resting expenditure, whichever name you meet.

Ballpark Maintenance Calories by Age and Sex

If you do not want to calculate anything yet, the Dietary Guidelines for Americans 2020 to 2025 give rough maintenance ranges. Each range spans sedentary to active, so pick the low end if you sit most of the day and the high end if you are active.

Age	Women	Men
19 to 30	1,800 to 2,400 calories	2,400 to 3,000 calories
31 to 50	1,800 to 2,200 calories	2,200 to 3,000 calories
51 and older	1,600 to 2,200 calories	2,000 to 2,800 calories

These are population averages, not personal numbers. Your own maintenance depends on height, weight, and activity, so use the table to pick a starting point, then confirm it with the calculation above or the no-math method below. The ranges do not apply during pregnancy or breastfeeding.

Find Your Maintenance Without Formulas

Two methods work without any equation. The first is 10-day tracking: eat normally for 10 days, weigh and log everything with an app, and weigh yourself daily. If your weight stays steady, your average intake over those 10 days is close to your maintenance. If it drifts, adjust by the drift. The second is the NIH Body Weight Planner, a free tool from the National Institute of Diabetes and Digestive and Kidney Diseases that builds a personal plan from your weight, age, height, and activity, and shows both the calories to reach your goal and the calories to maintain it afterwards. It is designed for adults aged 18 and over. Either method beats guessing, and both give you a number you can subtract 300 to 500 from.

How a Calorie Deficit Causes Weight Loss

When food energy runs short, your body looks for backup fuel. The main backup is stored body fat, which is broken down and converted into usable energy. Keep the deficit going day after day and fat stores shrink, which shows up as weight loss on the scale.

A quick note on the famous 3,500-calorie rule: one pound of body fat stores roughly 3,500 calories, so a 500-calorie daily deficit should equal about a pound a week. Treat this as a useful estimate, not exact math. Water shifts, digestion, and metabolic changes mean real loss is rarely a perfect straight line.

One more thing a deficit cannot choose: where the fat comes off. Spot reduction is a myth. Your genetics decide the order, so patience matters more than any special trick.

How Big Should Your Calorie Deficit Be?

Bigger is not better. A small deficit is slow but easy to live with. A large deficit is fast but hard to sustain and easier to quit. Here is how the common sizes compare:

Daily deficit	Expected loss	Best for
250 calories	About 0.5 lb per week	Gentle approach, minimal hunger, easy to sustain for months
500 calories	About 1 lb per week	The sweet spot for most people: steady loss without misery
750 to 1,000 calories	1.5 to 2 lb per week	Aggressive; only with high protein, strength training, and ideally professional guidance

Most experts land on 300 to 500 calories per day as the healthy range for sustainable fat loss. As a safety floor, avoid dropping below 1,200 calories a day for women or 1,500 for men without medical supervision. Below that, nutrient deficiencies, muscle loss, and hormonal problems become real risks. This gradual pace matches the Mayo Clinic’s six strategies.

How to Calculate Your Calorie Deficit (Worked Example)

Here is the full calculation for a sample person, so you can see exactly how the numbers work. Then use our free calorie calculator to get your own numbers instantly.

Meet Sara: 35 years old, 165 cm tall, weighs 75 kg, lightly active (walks daily, desk job).

Step 1: Find BMR with the Mifflin-St Jeor equation. For women: (10 x weight in kg) + (6.25 x height in cm) – (5 x age) – 161.

(10 x 75) + (6.25 x 165) – (5 x 35) – 161 = 750 + 1,031 – 175 – 161 = 1,445 calories. That is what Sara burns at complete rest.

Step 2: Multiply by activity level to get TDEE. Lightly active uses a multiplier of 1.375.

1,445 x 1.375 = 1,987 calories. That is Sara’s maintenance level.

Step 3: Subtract the deficit. For about a pound a week, subtract 500.

1,987 – 500 = 1,487, rounded to about 1,490 calories per day. That is Sara’s weight-loss target.

Skip the hand math and calculate your own target here, or find your maintenance first with the TDEE calculator.

The Full Activity Multiplier Table

Sara’s example used only one multiplier. Here is the full table, so you can pick your own level and repeat her three steps with your numbers.

Activity level	Multiplier	What it means
Sedentary	1.2	Desk job, little exercise
Lightly active	1.375	Light exercise 1 to 3 days a week
Moderately active	1.55	Moderate exercise 3 to 5 days a week
Very active	1.725	Hard exercise 6 to 7 days a week
Extra active	1.9	Very hard exercise, or a physical job

Multiply your BMR by your row to get TDEE, then subtract your deficit. If you fall between two rows, pick the lower one first. It is better to start slightly conservative and adjust after two weeks of tracking.

A Second Worked Example: A Man

Meet Omar (illustrative, not a real person): 40 years old, 180 cm tall, weighs 85 kg, moderately active (trains 3 to 5 days a week).

Step 1: Find BMR with the Mifflin-St Jeor equation. For men: (10 x weight in kg) + (6.25 x height in cm) minus (5 x age) + 5.

(10 x 85) + (6.25 x 180) minus (5 x 40) + 5 = 850 + 1,125 minus 200 + 5 = 1,780 calories. That is what Omar burns at complete rest.

Step 2: Multiply by activity level to get TDEE. Moderately active uses a multiplier of 1.55.

1,780 x 1.55 = 2,759 calories. That is Omar’s maintenance level.

Step 3: Subtract the deficit. For about a pound a week, subtract 500.

2,759 minus 500 = 2,259, rounded to about 2,260 calories per day. That is Omar’s weight-loss target.

Validation research comparing the Mifflin-St Jeor equation against laboratory measurement found it lands within about 10 percent of the measured value for most healthy adults, which is why it is the default in most calculators. If your result and your real trend disagree after two honest weeks, trust the trend and adjust. Skip the hand math and use the calorie calculator to get your own numbers instantly.

The Other Formula: Harris-Benedict

If you meet an older calculator, it may use the Harris-Benedict equation instead. The revised 1984 version is: for men, 88.362 + (13.397 x weight in kg) + (4.799 x height in cm) minus (5.677 x age); for women, 447.593 + (9.247 x weight in kg) + (3.098 x height in cm) minus (4.330 x age). For Omar above, Harris-Benedict gives about 1,864 calories, roughly 84 higher than Mifflin-St Jeor. That pattern is typical: Harris-Benedict tends to read slightly high, and Mifflin-St Jeor is the more accurate default for most people. Either is a starting estimate, not a measurement.

Should Your Deficit Come From Diet, Exercise, or Both?

You can create a deficit two ways: eat less, move more, or combine both. In practice, diet does most of the heavy lifting. It is far easier to skip a 300-calorie snack than to burn 300 calories running, and most people overestimate how much their workouts burn.

That said, exercise earns its place for a different reason: it protects your muscle. In a deficit without resistance training, a meaningful share of lost weight can be muscle. Add two or three strength sessions a week plus daily walking and you keep the muscle while the fat goes.

One trap to avoid: eating back your exercise calories. Fitness trackers routinely overestimate calorie burn, sometimes by a lot. If your watch says you burned 400 calories and you eat 400 extra, your deficit may quietly disappear. Treat exercise as a bonus for health and muscle, not as calories you get to spend.

The Weekly Exercise Target

The Physical Activity Guidelines for Americans give a concrete weekly target for adults: 150 to 300 minutes of moderate intensity activity, such as brisk walking, or 75 to 150 minutes of vigorous activity, such as running, plus muscle strengthening activities for all major muscle groups on 2 or more days a week. For a deficit, that target does double duty: the aerobic minutes add to the deficit, and the strength days protect muscle. You do not need to hit it in week one. Start with daily walking plus two strength sessions, then build toward the minute target.

Should I Eat Back the Calories I Burn Exercising?

No. Fitness trackers overestimate calorie burn, so eating back those calories usually erases your deficit.

Treat exercise as a health and muscle bonus, and keep your food target fixed.

Can You Build Muscle in a Calorie Deficit?

Beginners and people with higher body fat often can, especially with high protein (1.6 to 2.2 g/kg) and strength training.

Advanced lifters usually need at least maintenance calories to grow.

Everyone can and should train to keep the muscle they have.

Do Keto, Fasting, and Weight-Loss Medicines Work Differently?

Short answer: no, they all work through the same deficit. Keto, paleo, vegan, and intermittent fasting diets lose weight when they make you eat fewer calories than you burn, not because of a special mechanism. That is why two very different diets can both work, and why none of them works when calories stay above maintenance.

The best test of fasting is the 2022 New England Journal of Medicine trial by Liu and colleagues: 139 adults with obesity followed the same calorie target for 12 months, half eating only between 8 am and 4 pm and half with no time limit. The fasting group lost 8.0 kg and the calorie-only group 6.3 kg, a difference that was not statistically significant. The eating window added nothing once calories were equal. Fasting is a scheduling tool that helps some people eat less, not a fat-burning shortcut.

GLP-1 medicines work through the deficit too, by reducing appetite so people eat less. They can be powerful, but they do not change the rules: an excessive deficit on them still risks muscle loss and nutrient gaps, and they work under medical supervision, not as a do-it-yourself shortcut. If you take one, your doctor should set the calorie floor, not an article.

The practical point is freeing: pick the eating pattern you can actually sustain, because the deficit underneath it is what does the work.

Can You Lose Weight Without a Calorie Deficit?

No. Every effective diet, including keto, fasting, and vegan diets, and every weight-loss medicine that works through appetite, works by creating a deficit.

The method varies, but the mechanism does not. If weight is falling and staying off, a deficit is present whether it was counted or not.

How Long Does It Take to See Results?

With a 500-calorie daily deficit, expect about a pound a week on average, but the timeline is not perfectly smooth. Here is what most people experience:

• Weeks 1 to 2: Fast early drop, mostly water weight as glycogen, the stored form of carbohydrate, depletes and releases its bound water. Do not mistake this pace for the long-term rate.
• Weeks 3 to 4: The scale slows to its real pace. Clothes start fitting a little looser.
• Weeks 5 to 8: Visible changes in the mirror and in photos. Other people may start noticing.
• Weeks 9 to 12: A real transformation if you stayed consistent. Time to recalculate your TDEE, because a lighter body burns fewer calories.

Weigh yourself no more than once a week, at the same time of day, and judge by the trend over weeks, not single weigh-ins. Daily fluctuations from water, salt, and digestion can easily hide a week of real fat loss.

How Long to Lose 5, 10, or 20 Pounds?

The 3,500 calorie rule gives a rough timeline. At 0.5 lb a week, each pound takes two weeks. At 1 lb a week, each pound takes one week. The table below is simple division, so treat it as a starting estimate: real loss slows as you get lighter, and the dynamic slowdown stretches every timeline.

Goal	At 0.5 lb per week	At 1 lb per week
5 lb	10 weeks	5 weeks
10 lb	20 weeks	10 weeks
20 lb	40 weeks	20 weeks

A 10 lb goal at 1 lb a week is 10 weeks on paper. In practice, expect it to take longer, because water shifts, tracking drift, and a falling TDEE slow the average. Use the table to pick a goal and a pace you can live with for months, then check your personal curve in the NIH Body Weight Planner or the maintenance calories guide.

How Long Does It Take to Lose 10 Pounds?

At 1 lb a week, about 10 weeks on paper; at 0.5 lb a week, about 20 weeks.

In practice, expect longer, because loss slows as you get lighter and water shifts hide progress. Visible changes usually show around weeks 4 to 8.

Judge by the trend over months, and recalculate your target every 4 to 6 weeks as your weight falls.

How Do You Know You Are Actually in a Deficit?

Knowing the signs saves you from guessing. A deficit that is working usually shows up as a steady downward trend in weekly weigh-ins over two to four weeks, not a daily drop. Clothes fitting looser and a falling waist measurement confirm it even when the scale stalls, because water can hide fat loss for a week at a time. Energy should stay mostly stable, and normal hunger before meals is expected.

What does not confirm a deficit is a single low weigh-in or a day of feeling hungry. A single reading is mostly water, and hunger alone cannot tell a 300 calorie deficit from a 1,000 calorie one. Judge by the trend, the waist, and steady energy together.

Two warnings complete the picture. Intense, constant hunger, fatigue, or rapid loss of more than 2 lb a week usually means the deficit is too large, not that it is working better. And if nothing moves for three to four honest weeks, the deficit probably is not there at all. Audit tracking before cutting deeper, using the checklist in this guide.

How Do I Know If I Am Eating in a Calorie Deficit?

Look for a steady downward trend in weekly weigh-ins over two to four weeks, looser clothes, and a falling waist measurement, with energy mostly stable and normal hunger before meals.

A single low weigh-in proves nothing, since water shifts dominate daily readings.

If nothing moves for three to four honest weeks, the deficit probably is not there: audit tracking, including oils, sauces, and weekends, before cutting deeper.

Does a Calorie Deficit Guarantee Weight Loss?

In principle, yes: sustained negative energy balance forces the body to use stored energy.

In practice, no single week is guaranteed, because water retention, tracking error, and a falling TDEE can hide fat loss for weeks.

A deficit guarantees the direction of travel over months, not a loss every week. If the trend is flat for a month of honest tracking, the deficit is smaller than calculated, not broken physics.

Why Am I in a Calorie Deficit But Not Losing Weight?

This is the most common frustration in weight loss, and it almost always comes down to one of these. Work through the checklist honestly:

• Tracking is off. Cooking oils, sauces, dressings, coffee creamer, and weekend meals are the usual suspects. Even small daily misses of 200 to 300 calories can erase a modest deficit.
• Weekends undo the week. Five clean days plus two untracked days often averages out to maintenance. The math only works if all seven days count.
• Water retention is masking fat loss. New exercise routines, salty meals, stress, poor sleep, and hormonal cycles all cause water retention that hides fat loss on the scale for weeks.
• You never recalculated. As you lose weight, your TDEE drops. A deficit calculated three months ago may be maintenance today. Recalculate every 4 to 6 weeks.
• Metabolic adaptation. Long deficits cause the body to burn slightly less (often around 100 calories a day). Real, but smaller than most people fear, and reversible.
• Sleep and stress. Short sleep raises hunger hormones and cravings. Chronic stress does the same through cortisol, plus water retention.
• Medical factors. Thyroid issues, PCOS, and some medications (including certain antidepressants and steroids) can slow or block fat loss. If everything above checks out, see a doctor.

Important: if the answer is “my deficit is not working,” the fix is usually not to cut deeper. Audit your tracking first. Sometimes the right move is a short diet break at maintenance, not a bigger cut.

Make Tracking Accurate: A Food Scale and an App

The stall checklist says to audit tracking, but here is how to do it properly. Weigh food with a kitchen scale for two weeks, and log everything in a calorie tracking app, including oils, sauces, drinks, and weekend meals. A scale beats eyeballing portions, which is where most 200 to 300 calorie daily errors come from. Two honest weeks of weighed tracking either confirms the deficit or finds the leak, and either answer is progress. After that, you can relax the weighing once you know what your portions actually look like.

Does a Calorie Deficit Slow Your Metabolism?

Partly true, mostly misunderstood. In a prolonged deficit, the body adapts by burning a little less energy, a process called adaptive thermogenesis. You fidget less, workouts feel harder, and your BMR dips slightly. For most dieters this amounts to roughly 100 calories a day, not a broken metabolism.

The popular idea of “starvation mode”, where the body supposedly stops losing fat entirely, is greatly overstated. True metabolic shutdown happens only in actual starvation. What feels like a broken metabolism is usually a mix of the checklist above: tracking drift, water retention, and a TDEE that quietly dropped as you got lighter.

The fix is straightforward: take diet breaks. Every 8 to 12 weeks, eat at maintenance for one to two weeks. This eases diet fatigue, restores energy, and makes the next deficit phase easier to sustain. It does not erase your progress.

One more adaptation deserves a name: NEAT, or non-exercise activity thermogenesis. That is the calories you burn through everything that is not formal exercise: walking to the kitchen, standing, fidgeting, doing housework. During a long deficit, NEAT quietly falls as the body conserves energy, which is one reason a deficit that worked in month one stalls in month three even when food and workouts have not changed. Daily steps are the simplest way to watch it: if your step count has slipped, restoring it often restores the deficit without cutting food further. For the walking side, see the steps guide.

Does a Calorie Deficit Damage Your Metabolism?

Not permanently. Long deficits cause a modest slowdown called adaptive thermogenesis (often around 100 calories a day), which reverses when you return to maintenance.

Regular diet breaks prevent most of it.

Signs Your Calorie Deficit Is Too Big

An aggressive deficit announces itself. Watch for these warning signs and take them seriously:

• Constant fatigue and poor concentration
• Hair thinning or hair loss
• Always feeling cold
• Extreme, intrusive hunger or binge episodes
• Irritability and low mood
• Missed or irregular periods
• Workouts getting weaker instead of stronger

If several of these show up, your deficit is too large. Raise your calories by 200 to 300 a day or take a full diet break at maintenance for two weeks, then resume with a smaller deficit.

A Warning on Very Low Calorie Diets

A very low calorie diet, or VLCD, means about 800 calories a day or less, usually as meal replacement formulas, for 12 to 16 weeks under a health care provider’s supervision. It is a medical treatment, not a bigger version of a normal deficit. The main serious risk is gallstones: studies found 10 to 25 percent of people on a VLCD developed gallstones, most without symptoms, though about a third of those had symptoms and some needed gallbladder surgery. VLCDs are not suitable during pregnancy or breastfeeding, for children or teens outside specialized programs, or for anyone without medical supervision. If a plan promises VLCD results without a doctor, walk away.

A very low calorie diet, or VLCD, provides about 800 calories a day or less, usually as meal replacement formulas, for 12 to 16 weeks under a health care provider’s supervision. It is a medical treatment, not a DIY plan.

The main serious risk is gallstones, found in 10 to 25 percent of people studied on VLCDs.

It is not suitable during pregnancy or breastfeeding, for children or teens outside specialized programs, or without medical supervision.

Who Should Talk to a Doctor First?

Most healthy adults can start a modest 300 to 500 calorie deficit safely. But talk to your doctor before starting if any of these apply to you:

• You are pregnant, breastfeeding, under 18, or underweight.
• You have type 2 diabetes, kidney problems, high or low blood pressure, thyroid problems, or a heart condition.
• You have a history of an eating disorder, or a troubled relationship with food.
• You take daily medication that affects weight, appetite, blood sugar, or blood pressure.
• You have been told to gain weight, or you have lost weight without trying.

This is not a full screening list, and it is not a substitute for medical advice. If anything on it applies, a short conversation with your doctor sets a safe calorie floor and checks for causes that diet alone cannot fix. The rest of this guide assumes a healthy adult. If that is not you, get personal advice first.

What to Eat in a Calorie Deficit

No foods are forbidden, but some make a deficit dramatically easier to live with:

• Protein first: aim for 1.6 to 2.2 grams per kilogram of body weight daily. It preserves muscle and is the most filling macronutrient.
• Fiber and volume: vegetables, fruits, legumes, and whole grains fill your stomach for few calories.
• Whole foods over liquid calories: sugary drinks and alcohol add calories without fullness. They are the easiest cuts to make.
• Plan your treats: a small daily dessert you enjoy beats a “perfect” week followed by a binge.

A sample day at 1,500 calories: Greek yogurt with berries for breakfast, grilled chicken salad for lunch, an apple and a protein shake as snacks, and salmon with roasted vegetables and rice for dinner. Filling, high in protein, and no suffering required.

Two cheap adherence tips round out the food section. First, drink water before meals and through the day: thirst is often mistaken for hunger, and a glass of water before eating helps some people eat less without trying. Second, consider a basic multivitamin while cutting, since a smaller food intake can leave gaps in vitamins and minerals. Neither replaces food or fixes a bad deficit, but both make a good one easier to hold. If you take medication or have a condition that affects nutrient needs, ask your doctor which supplement, if any, suits you.

Food Swaps That Create a Deficit Without Hunger

The easiest deficit is the one you do not feel. Swaps cut calories while keeping the meal familiar, and they are the practical side of the “what to eat” advice above.

Swap	Why it helps
Sugary drinks for water or unsweetened tea	Removes liquid calories that never fill you up
Sour cream for nonfat Greek yogurt	Similar texture, far more protein per calorie
Fatty cuts for lean meat or fish	Same portion, less fat per bite
Half the pasta or rice for nonstarchy vegetables	Same plate volume, fewer calories, more fiber
Cooking at home most nights	You control oils, sauces, and portions

The biggest single category to cut is ultra-processed foods: packaged snacks, ready meals, sugary cereals, and processed meats. In a tightly controlled 2019 trial by Hall and colleagues, 20 adults ate about 508 calories a day more on an ultra-processed menu than on an unprocessed menu matched for nutrients, and gained weight on the former while losing it on the latter. Ultra-processed foods are easy to overeat because they are soft, calorie dense, and engineered to be tempting. Swapping even part of them for whole foods often creates the whole deficit by itself.

Pick two or three swaps and hold them for two weeks before adding more. A deficit built on swaps lasts longer than one built on willpower alone.

After the Goal: Moving Back to Maintenance

Reaching your goal is not the end of the plan. It is the start of maintenance, and most regain happens here. Raise calories gradually over several weeks until weight stabilizes, rather than jumping straight back to your old intake, and keep protein high and strength training in place while you do it.

Expect a small initial rise on the scale, usually a few pounds, as glycogen stores refill and bring water with them. That is not fat regain. It is the reverse of the fast early drop at the start of the deficit. Judge maintenance by the trend over four weeks, not by the first week’s bounce.

Keep the habits that maintain weight: weigh weekly, keep a waist check monthly, and recalculate your maintenance at your new weight with the maintenance calories guide. If weight climbs steadily for a month, a short return to a small deficit corrects it before it becomes a full regain.

Sources

• U.S. Department of Health and Human Services. Physical Activity Guidelines for Americans: 150 to 300 minutes of moderate intensity or 75 to 150 minutes of vigorous activity per week, plus muscle strengthening on 2 or more days.
• U.S. Department of Agriculture and U.S. Department of Health and Human Services. Dietary Guidelines for Americans, 2020 to 2025: estimated calorie needs by age, sex, and activity level.
• Hall KD, Ayuketah A, Brychta R, et al. Ultra-processed diets cause excess calorie intake and weight gain: an inpatient randomized controlled trial of ad libitum food intake. Cell Metabolism, 2019. PubMed
• Liu D, Huang Y, Huang C, et al. Calorie restriction with or without time-restricted eating in weight loss. New England Journal of Medicine, 2022. DOI
• Frankenfield D, Roth-Yousey L, Compher C. Comparison of predictive equations for resting metabolic rate in healthy nonobese and obese adults: a systematic review. Journal of the American Dietetic Association, 2005. PubMed
• National Institute of Diabetes and Digestive and Kidney Diseases. NIH Body Weight Planner, a free tool for adults to plan calorie and activity targets.
• National Institute of Diabetes and Digestive and Kidney Diseases. Dieting and Gallstones: very low calorie diets of about 800 calories a day or less, used for 12 to 16 weeks under supervision, with gallstones in 10 to 25 percent of people studied.
• Risk of symptomatic gallstones and cholecystectomy after a very low calorie diet or low calorie diet in a commercial weight loss program: 1-year matched cohort study. PMC

This guide is general information, not medical advice. If you have diabetes, kidney problems, a hormone condition, take daily medication, are pregnant or breastfeeding, or have any condition that affects weight, talk to your doctor before changing your diet or exercise routine, and use this guide as background, not as a prescription.

Frequently Asked Questions

Calculate Your Numbers Now

Reading about deficits is step one. Step two is knowing your numbers. Use our free tools: the TDEE calculator finds your maintenance level, the calorie calculator sets your deficit target with a full macro split, and the BMI calculator tells you where you are starting from.