Thursday, 7 March 2013

Diet Stuff (1): My Numbers

At the moment I weigh just over 90 kgs (198 lbs), down, thanks to a bout of food poisoning, from what had been a stable 92 kgs. That's not a viable long-term weight-loss regime, though it got me to 89.5 kgs, or just over 14 stone. (Being English, I still think in terms of Stones.) At university I was about 11 stone (69 kgs, 154 lbs). When I started weight-training, I was around 13 stone (82 kgs, 182 lbs). My new-scale BMI comes out at 26.8, but every doctor in the world takes one look at me and tells me to ignore it. I'm clearly not a Fat Bastard, I am clearly a Big Fit Man. To be BMI-friendly, I would need to be back at 82 kgs again. That's an 8 kgs (17 lbs) loss. My body-fat is around 23% - don't you dare say a word - and it always has been. On a really good day I can get down to 21%. Let's say I lost all those 8 kgs in fat. That would put my body fat around 15%. According to some calculator at my age, 15% is "lean" and 23% is "ideal". At 15% I would look like a freaking Greek God. Seriously. So how about losing more of the weight in body fat than muscle? When I very first started at the gym, and held on to a vicious 1,500 calorie / day diet, I got down to about 85 kgs and 20.5% body fat, but that was unsustainable.

According to this calculator I need 2,400 calories a day to "maintain" my weight. 1,500 would be "extreme" fat loss, and 1,900 would be "regular fat loss". 

Know what the difference between 1,500 and 1,900 calories is? Or between 1,900 and 2,400 calories? It's a 120g bar of chocolate, or six digestive biscuits, or a Pret smoked salmon sandwich, your five-a-day fruit choice, a Krispy Kreme donut... You get the picture. One slip and you've blown your diet for the day. My carrot/parsnip/beans/onion and tomato stew is about 300 calories (I use larger vegetables). A Pret Tuna sandwhich is 550 calories. Two eggs and ham for breakfast, with a small fruit smoothie, is about 500 calories.

The idea anyone can lose weight by cutting out a couple of biscuits a day is simply silly. Mainly because while they might be able to control their food intake, they can't decree the day-to-day calorie burn their body decides it's going to do. Your body does not burn a constant amount every day. You can't find a measure of the variation, so I'm allowed as a first approximation to assume a 10% coefficient of variation on a Normal distribution. In other words, to be 95% sure I am always eating less than my body is burning, I need to be eating 80% (two standard deviations) of 2,400, or 1,920 calories a day. I know you're going to point out that a 1,920 calorie day should be balanced by a 2,400 calorie day, but we both know it doesn't work like that. You're slower more days than you're quicker. The distribution isn't really Normal - it's skewed over to the slower side. So if I really want to cut down the weight at a speed that gets you results this side of next year, it's 1,500 calories a day for me. 

The standard calculation is that a kilo of fat is 7,700 calories (3,500 calories / lb x2.2 lbs / kg). With a "maintain" of 2,400 and an actual of 1,500, that's 1kg every nine days. That's 72 days, or eleven weeks. Isn't that do-able with a bit of will-power? Three months at 1,500 calories a day? Yeah. Sure. 

Damn good thing it doesn't work like that.

No comments:

Post a Comment