Most adults don’t need to aim to “burn” a specific number of kJ with exercise alone each day; instead, the goal is to balance total kilojoules eaten and total kilojoules used (basal metabolism + movement) so your weight goes in the direction you want.

Key idea: total kJ in vs out

  • The average adult needs around 8,700 kJ per day to maintain weight, but this can be higher or lower depending on age, sex, body size, and activity level.
  • Weight loss happens when total kJ burned in a day is higher than total kJ eaten, creating a sustainable deficit (usually a few hundred kcal / ~1,000–2,000 kJ per day for many people, though this is very individual and should ideally be guided by a professional).

So how many kJ should you burn?

Instead of “how many kJ should I burn a day?”, a more useful question is:

What’s my total daily energy use, and how big a deficit is safe?

  • Many guidelines estimate total daily needs in the ballpark of roughly 145–200 kJ per kg of body weight per day for adults at various activity levels, which works out to about 9,000–12,000+ kJ per day for many people.
  • Public health guidance often uses ~8,700 kJ as a typical maintenance number for an “average” adult, but emphasizes that your personal requirement can differ a lot.

Practical way to think about it

  • Step 1: Estimate your daily needs with an online “daily energy requirements” or “kilojoules calculator” that asks for your age, sex, height, weight, and activity level.
  • Step 2:
    • If you want to maintain weight, roughly match your total daily kJ intake to that estimate.
* If you want to **lose** weight, reduce intake and/or increase movement so that your total kJ eaten is a bit _below_ that estimate, while still eating enough to feel reasonably well and nourish your body.

What about exercise specifically?

  • Exercise is only one part of your daily burn; most of your kJ use comes from your body just running itself (your basal metabolic rate), plus general movement.
  • For many people, a realistic target is to move enough that you add a few hundred extra kcal of activity per day (roughly 800–1,500 kJ), through walking, workouts, or active hobbies, while adjusting food so that the total equation works for your goal.

Important health notes

  • Extremely low intake or trying to “burn off” huge amounts of kJ every day can be unsafe and hard to sustain; medical and nutrition guidelines recommend individualized plans rather than one blanket number for everyone.
  • If you have medical conditions, take medications, or have a history of disordered eating, it is especially important to talk with a doctor or dietitian before setting aggressive burn or deficit targets.

If you share your age, sex, height, weight, and how active you are, a more tailored explanation of your likely daily kJ needs and a sensible burn/deficit range can be outlined for you.