First, we need to establish your BMR (basal metabolic rate), this will give us a rough idea of what you expend throughout the day to just keep that body ticking over at rest (not factoring in ANY daily activity or exercise, basically just sitting in isolation all day ).
One of the most accurate equations for this is the “Harris Benedict” as it takes into account, height, age, gender, and weight.
HARRIS BENEDICT EQUATION:
66+ (13.7 x BW in KG) + (5 x Height in CM)
– (6.8 x Age)
655+(9.6 x BW in KG)+(1.8x Height in CM)
– (4.7 x Age)
E.G. A 31YO FEMALE WHO WEIGHS 67KG AND IS 163CM TALL:
655+(9.6x67kg=643) + (1.8x163cm=293)
BMR = 1445 Calories per day
We now need to multiply this number by our physical activity level (PAL) to give us our MAINTENANCE calories (the amount we need to eat to remain the same weight/support the exercise and activity we do).
CHOOSE YOUR PAL:
Sedentary (little or no exercise) = x 1.2
Lightly active (training/sports 2-3 days a week) = x 1.3-1.4
Moderately active (training/sports 4-5 days a week) = x 1.5-1.6
Very active (training/sports 6-7 days a week) = x 1.7-1.8
Extremely Active (twice per day, extra heavy workouts) = x 1.9
E.G. 1445X1.5= 2168 MAINTENANCE CALORIES PER DAY
For weight loss we need to be in a calorie deficit (consuming fewer calories than you burn daily) So now you need to create your deficit.
How quickly you lose weight depends on how big that deficit is but for health and adherence usually a 20% deficit brings the best results (in our opinion):
2168 X 0.20 (20%)= 434 CALORIE DEFICIT
WEIGHT LOSS CALORIES =1734 CALORIES/DAY (2168-434)
Remember this is only a starting point and we can get more meticulous, taking into account ALL the non-exercise activity (walking to the shops, hoovering the house) you do. But for most just getting started tracking and understanding calories is enough.