They say the last two kilograms are the hardest to lose, but we’ve found a loophole.
Calculate your baseline
Basal metabolic rate (BMR) is the number of calories you’d burn per day if you were to lie in bed 24/7. It’s based on various factors including your height, age and body composition (a higher muscle to fat ratio will burn more calories even at rest). To calculate your BMR, plug your deets into this equation (known as the Harris-Benedict equation):
BMR = 655 + (9.6 x weight in kg) + (1.8 x height in cm) – (4.7 x age in years)
e.g. a 30-year-old female measuring 167 cm tall and weighing 54.5 kg would compute 655 + 523 + 302 – 141 to get a maintenance level daily calorie need of 1,339, or 5,624 kJ, per day (multiply calories by 4.2 to convert to kJ lingo).
If your numbers come in low, don’t panic. In addition to what you burn to maintain basic bodily functions, you need to add your other energy usage. What you want to work out how many kJs you’re burning on average per day, and how many kJs you need to cut to lose your target kilos, is your total daily energy expenditure (TDEE), which comprises BMR (65 per cent), physical activity and thermic effect of food.
To calculate your TDEE, multiply your BMR by your activity level according to these numbers.
Sedentary = BMR x 1.2 (little or no exercise, desk job)
Lightly active = BMR x 1.375 (light exercise / sports 1–3 days/week)
Moderately active = BMR x 1.55 (moderate exercise / sports 6–7 days/week)
Very active = BMR x 1.725 (hard exercise every day, or exercising 2 times/day)
Extra active = BMR x 1.9 (hard exercise 2 or more times per day, or training for marathon, or triathlon, etc.)
e.g. If your BMR is 1,339 calories, or 5,624 kJ, and you’re lightly active, your activity factor is 1.375, making your TDEE 1.375 x 1,339 or 5,624, or 1,841 calories/7,733 kJ. In theory consuming 7,733 kJ each day (or 54,129 kJ a week – there’s no penalty for zig-zagging to accommodate a dinner party) will maintain your current weight.
Based on the 0.5 kg a week deemed optimal, you’ll need a cumulative deficit of 14,700 kJ a week (there are 14,700 kJ in half a kilo of body fat). A weekly deficit of 7,350 kJ will translate to loss of 0.25 kg per week. Aim to eat approximately the same amount of kJs each day, but don’t get obsessive. If you want to go out for parma (around twice the kJs in a Lean Cuisine dinner), shoot for 1,000 kJ less than your loss needs the following day and you’ll come out square.
You can’t out-train a bad diet because it’s so much easier to consume calories than burn them. (A flavoured milk packs in more than an hour’s workout burn in a few gulps.) Yet exercise can give you an extra food allowance. By burning 400 calories in spin class, you can still eat 7,080 kJ and lose your half a kilo a week.