Mathematics of weight gain/loss

I’m aiming to lose14 lb (1 stone ) before 24 December 2011!! As I have always been one to apply science and math to things,  this represents my analysis of the situation.

Weight loss will take place if the Present Total Calorie Need (PTCN) is not met over some long period.

PTCN = Basal Metabolic Rate (BMR) + Activity Expenditure Requirement (AER)

Women: BMR = 655 + ( 4.35 x weight in pounds ) + ( 4.7 x height in inches ) – ( 4.7 x age in years )
Men: BMR = 66 + ( 6.23 x weight in pounds ) + ( 12.7 x height in inches ) – ( 6.8 x age in year )

PTCN is determined by Harris Benedict Formula (which caters for AER):

  1. Sedentary (little or no exercise) : Calories required = BMR x 1.2
  2. Lightly active (light exercise/sports 1-3 days/week) : Calories required = BMR x 1.375
  3. Moderately active (moderate exercise/sports 3-5 days/week) : Calories required = BMR x 1.55
  4. Very active (hard exercise/sports 6-7 days a week) : Calories required = BMR x 1.725
  5. Extra active (very hard exercise/sports & physical job or 2x training) : Calories required = BMR x 1.9

I’ll use a woman of say age 38, 135 1b, 5’ 6’’ with a sedentary lifestyle as an example (no it’s not you, just calm down – no need to pull the curtains!! LOL) –

BMR[f] = 665 + (4.35 x 135) + (4.7 x 66) –(4.7 x 38) = 1384 calories/day

Predicted PTCN for sedentary woman would be 1383 x 1.2 = 1661 (that’s not a lot!!)

1 lb of fat in any person represents 3500 calories. That is the deficit to be created over some time to lose 1 lb. It doesn’t matter if you avoid sweet things, eat pasta, eat healthy, jump on the spot – only the mathematics is what matters!

In essence there are three ways of creating the deficit – and these can work together.

  1. Reduce calorie intake – in practice ‘calorie’ starvation is not a good idea because the body compensates by reducing BMR as a protective mechanism. Most people will sensibly wish to create a 500 calorie per day deficit over several weeks, from dieting alone.
  2. Increase calorie expenditure  – this can be increased by exercise by about 500 calories per day.
  3. Increase BMR – this is not easy. However, increasing muscle mass by proper and sustained weight training can increase BMR over a long period of time.

Well all that is the math and the basic science. Now to apply it!! That’s the hardest part – isn’t it? LOL. I’m weighing myself every morning at around 07:30-ish – after taking care of excretion etc. Gotta get this standardised and consistent – innit. Winking smile

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