By the Medsmingle Team · Updated 11 November 2026
To lose weight, you need to take in fewer calories than your body burns. This is called a calorie deficit. Your calorie needs depend on your size, health, age and activity. A clinician or registered dietitian can help set an appropriate goal; gradual weight loss is generally more sustainable than a crash diet.
What is a calorie deficit?
Your body burns calories all day, both to keep you alive and to fuel movement. When you take in fewer calories than you burn, your body uses its stored energy to make up the difference, and you lose weight. You can create a deficit by eating less, moving more, or both.
How many calories do you burn?
It depends on your age, sex, size and how active you are. These US government estimates show roughly how many calories adults need each day to stay at the same weight:
| Age and activity | Women (calories a day) | Men (calories a day) |
|---|---|---|
| 19 to 60, not active | 1,600 to 2,000 | 2,200 to 2,600 |
| 19 to 60, active | 2,200 to 2,400 | 2,600 to 3,000 |
| 61 and over, not active | 1,600 | 2,000 |
| 61 and over, active | 2,000 | 2,400 to 2,600 |
For a personal estimate, try the NIH Body Weight Planner. It makes a calorie and activity plan to reach a goal weight by a set date, and to keep it off afterwards.
How big should your calorie deficit be?
There is no calorie target that is right for everyone. Choose a balanced eating plan and a manageable change in activity with your healthcare professional. Do not use a very low-calorie diet without medical supervision. Get individual advice if you are pregnant, breastfeeding, under 18, take diabetes medicines, or have a history of an eating disorder.
Why “3,500 calories = 1 pound” doesn’t hold up
You may have read that cutting 3,500 calories loses a pound, so a 500-calorie daily deficit loses exactly a pound a week. NIH researchers have shown this rule overestimates weight loss because it ignores how your body changes as you lose weight. As you get lighter, you burn fewer calories, so the same eating plan gives a smaller deficit and weight loss slows.
That’s normal, not failure. Re-check your calorie needs as your weight changes. If your weight has stopped moving for several weeks, read our guide to the weight-loss plateau.
How to cut calories without feeling starved
- Keep a food diary for a week or two. It shows where small changes would make the biggest difference. Count drinks, alcohol, cooking oils, toppings and sauces too.
- Check labels and portions. Weighing food, at least at first, makes your estimates more accurate.
- Build meals around protein, vegetables and fiber. They help you feel full on fewer calories; see how much protein for weight loss you need.
- Move more. Regular physical activity is one of the CDC’s steps for losing weight, and it burns extra calories. Walking is an easy place to start.
- Sleep and manage stress. The CDC includes enough sleep and stress management in its steps for losing weight.
What results to expect
Even a modest loss helps. According to US guidelines, losing 3% to 5% of your body weight brings real health benefits, and losing more than 5% can further improve blood pressure and cholesterol. For someone who weighs 200 pounds, 5% is 10 pounds.
If you have a lot of weight to lose, structured support helps. Guidelines recommend a comprehensive lifestyle program lasting at least 6 months. A doctor can also tell you whether other treatments might suit you.
Frequently asked questions
Is 1,200 calories a day right for everyone?
No. It can be too little for many people. Your needs and an appropriate deficit should be assessed individually.
Why have I stopped losing weight?
As you lose weight, your body burns fewer calories, so the deficit you started with shrinks. Re-check your numbers, and look at your activity, sleep and portion sizes.
Should I cut calories or exercise more?
Both help. The CDC recommends combining healthy eating with regular physical activity, rather than relying on one alone.
Sources
- Steps for Losing Weight, Centers for Disease Control and Prevention (CDC)
- 2013 AHA/ACC/TOS Guideline for the Management of Overweight and Obesity in Adults, American College of Cardiology
- Calorie counting, NHS Better Health
- Estimated Number of Calories Needed Based on Age, Sex, and Activity Level, MSD Manual (from the Dietary Guidelines for Americans, 2020–2025)
- About the Body Weight Planner, NIDDK
- Why is the 3500 kcal per pound weight loss rule wrong?, Hall KD and Chow CC, International Journal of Obesity (2013)
This article is for general information only and isn’t a substitute for advice from a doctor or pharmacist. Don’t start, stop or change a medicine without talking to a qualified healthcare professional.
