Since the weather was pretty crappy today, and I'm not going to get in a bike ride, I thought I'd let the engineer in me take over and run some numbers regarding getting back into shape.
So, here's the fundamental logic behind my routine. The human body burns some number of calories every day, just by keeping itself alive, and it burns additional calories through any additional physical activities - walking around, exercising, etc. If you want to lose weight, you must maintain what's called a caloric deficit - in other words you must consume fewer calories than you burn.
So the first thing I did was calculate an estimate of how many calories a day I need, called my Resting Metabolic Rate. Note: resting metabolic rate is what most people mean when they reference basil metabolic rate. BMR is the energy required by the body to keep itself alive, period. RMR is the energy used by the body at a state of slacking off. What's the difference? Well, for one, RMR accounts for energy used digesting food, where BMR requires your digestive system to be "shut down" (after a 12 hour fast, it has nothing to do). RMR provides a more accurate estimate of your caloric requirements sitting at your desk job all day long.
Unfortunately, though, there are several commonly used ways of calculating RMR. Many only take into account your body weight - and these are the most inaccurate. More accurate estimates use your body weight, height and age. These are the equations commonly used in online calculators. While fairly accurate, neither take into account your body-fat-percentage. If you are very muscular, the equations will under-estimate your caloric requirements, and if you are over-weight, the equations will over-estimate your caloric needs (because muscle burns more calories than fat to maintain itself)
A better equation takes into account your Body Fat Percentage. Estimating your Body Fat Percentage, is yet another task, though, for which there are several methods. One of the simplest is the "Height and Circumference method":
BFP = ((4.15 * waist in inches) - (0.082 * weight in pounds) - s) / weight
Where s is 76.76 for women, and 98.42 for men.
Once you know your BFP, you can calulate your RMR using the equation:
P = 370 + ( 21.6 * weight in kg * (1-BFP) )
I won't run through my personal numbers here (for the sake of saving space). My RMR came out to 1,828 kcal using a BFP of 25%. That tells me I need to eat 1,828 calories a day in order to maintain my current weight. Note, also, that my RMR obviously does not take into account my daily bike rides. My 75 minute ride with an average speed of 12-13 MPH burns about 960 calories (I looked it up). So, on a day when I bike, I need to consume 2,788 calories to maintain weight.
So my basic calorie requirements are 1,828 calories on non-work-out days, and 2,788 calories on work-out-days. To lose weight, through, I need to introduce the calorie deficit, for which I have two options:
- Consume fewer calories
- Increase my physical activity to burn more calories
Of course, I am doing both. It seems to be common sense among exercise forums and other sources on the internet that maintaining a defecit of 500 calories a day is safe, effective, and will cause you to lose 1 pound per week (there are 3500 calories in a pound of fat. So after a week of 500 calorie daily deficit, you've burned 3500 stored calories, and lost 1 pound). Unfortunately, I have NEVER eaten 2,788 calories a day (not in real food, anyway). So for me, even eating 2,288 calories a day (which represents a 500 calorie deficit) would be quite daunting.
I have introduced breakfast into my routine, and snack on fruits and veggies throughout the day, and follow it up with a healthy dinner (something along the lines of salad and grilled meet, chicken, or fish). Over the past week, I have only been taking in maybe 750 calories a day - which is clearly too low. I will try to increase that to somewhere between 1,200 and 1,500 calories a day to promote higher metabolism.
Then, on days when I do not work out, I will have a minimum deficit of 328 calories, and on days when I do, a minimum deficit of 1,288 calories. In an average week then, say I bike 5 days, I would have a weekly deficit of 7,096 calories and have lost 2.02 pounds that week.
Final note -- you should concern yourself with two additional points:
- WHERE exactly your body gets calories to make up for the deficit in your diet, and
- Where the calories you do eat come from.
Your body will grab additional calories by burning fat and muscle tissue. So it's important to throw in some light-to-moderate weight training or callisthenics into your routine as well. This will help maintain and protect muscle mass, and force your body to get the necessary calories from fat tissue instead. Not to mention, it'll further increase the number of calories burned too, accelerating the whole process, and help tone and shape while you lose fat. Also, keep a watchful eye not only on the fat content of the food you eat, but on the "calories from fat." The USDA recommends that no more than 30% of your calories should come from fat, and I'd recommend less than that if you're trying to burn fat off.
So there you have it - my analytical mind pushing me to eat right and bike more through simple arithmetic and introductory thermodynamics. I knew that course would be good for something.