Basal Metabolic Rate (BMR)
It stands to reason that if you want to lose weight one of the first things you need to know is how many kcal you should consume each day. What’s the max you can eat without putting on weight and how much less than that should you eat to start losing weight?
Now all the guidelines say that the average woman should eat about 2000 kcal per day. They also reckon that to lose weight you should reduce your calorie intake by 300-500 kcal per day. One pound of fat equals 3500 kcal so by reducing your daily kcal intake by 500 kcal per day you should lose one pound per week. But what if you’re not an average woman? If you’ve ever done Weight Watchers you’ll know that the heavier you are the more you get to eat and still lose weight. As you lose weight you need to decrease how much you eat to maintain the weight loss. This is because most of the energy you consume is spent simply keeping your body alive - the bigger your body the more food it needs just to maintain itself.
The key is to work out your Basal Metabolic Rate (BMR) - this is your daily energy requirement. For women you work it out thus:
BMR = 655 + (9.6 x weight in kg) + (1.8 x height in cm) - (4.7 x age in years)
For me this works out as
BMR = 655 + (9.6 x 86.6 kg) + (1.8 x 163 cm) - (4.7 x 32) = 655 + 831 + 293 - 150 = 1629
You then have to multiply this figure by the activity factor (for women) that applies to you: inactive (desk job, little or no exercise) 1.4; light (some light daily exercise) 1.5; moderate (regular exercise) 1.64; heavy (manual job or athlete) 1.82.
I’m lazy therefore I get:
1629 x 1.4 = 2280 kcal per day.
Therefore to maintain my current weight I need to eat 2280 kcal per day. But in order to lose between 0.5lb and 1lb of weight each week I would need to reduce this to between 1800-2000 kcal per day. Furthermore as I lost weight I would need to repeat the above calculations with my new weight and adjust my diet accordingly as my BMR decreased with my shrinking body size. Of course to aid weight loss I could also increase my activity levels. Hmm, can’t see that happening, at least not until I’m thin enough to dare to walk into a gym.
Now I just need to know what I’m supposed to eat to achieve this.