What is a calorie deficit?
A deficit is the gap between your maintenance energy and what you actually eat. If you burn 2,200 Cal (9,200 kJ) and eat 1,700 Cal (7,100 kJ), you are in a deficit of about 500 Cal (2,100 kJ) a day.
A simple five-step plan
- Calculate maintenance. Use the calculator and pick an honest activity level.
- Subtract 10–20%. That is about 275–550 Cal (1,150–2,300 kJ) for most adults. Bigger cuts increase hunger, muscle loss and the chance of rebound.
- Track for 2–3 weeks. Use the kJ figures on Nutrition Information Panels or an app that supports kilojoules. Weigh food at least occasionally to calibrate portion sizes.
- Check the trend. Weigh daily or a few times a week and compare weekly averages, not single readings.
- Adjust slowly. Change intake by 100–200 Cal at a time.
Protect muscle while you lose fat
- Strength train 2–3 times a week.
- Aim for roughly 1.6 g of protein per kg bodyweight spread over the day.
- Keep the deficit moderate. Rapid loss costs proportionally more lean mass.
Eat well, not just less
The Australian Dietary Guidelines recommend plenty of vegetables, fruit, wholegrains, lean proteins and healthy fats while limiting discretionary foods like alcohol, sweet drinks and processed snacks. A deficit built on nutritious, filling foods is easier to maintain.
Plateaus
If your weight hasn't changed in 3–4 weeks, check tracking accuracy first, then trim 100–200 Cal or add daily steps. Planned breaks at maintenance for 1–2 weeks can help with adherence.
When a deficit isn't appropriate
Do not use a deficit if you are pregnant or breastfeeding, under 18, underweight, or have a history of disordered eating. If food or weight preoccupies you, contact your GP or the Butterfly Foundation National Helpline on 1800 33 4673. People with diabetes or other conditions should discuss any change in intake with their doctor first.