Want to gain or lose weight? It's all about Net Calories!
I originally wrote this for a fitness forum, then posted it to calories.io. I may replace calories.io with an app someday, so I'll archive this article here on my blog.
Your "Net Calories" is one of the most (if not THE most) important statistics for weight change (up or down).
Net Calories is the caloric value of the food you consumed in a day, minus your BMR x 1.2, minus calories burned in exercise. So if you eat 1500 calories, and your BMR is 1500, and you burned 300 calories in exercise, your net calories for the day are -600, a deficit of 600 calories. If you maintain this for a week, your deficit for the week will be 4200 calories, which equates to 1.2 lbs of fat loss.
Understanding Net Calories
To figure everything out, start by calculating your Basal Metabolic Rate (BMR). This is the number of calories you burn just being ALIVE. If you were lying in bed all day, and didn't even have food in your system (meaning your digestive system was not even running), you'd burn this many calories. So, how do we estimate your BMR?
- Men: BMR = 66 + (6.23 x weight in pounds) + (12.7 x height in inches) - (6.8 x age in years)
- Women: BMR = 655 + (4.35 x weight in pounds) + (4.7 x height in inches) - (4.7 x age in years)
Do it yourself for the practice, or use an online calculator. If you do use an online calculator, make sure it doesn't ask you how active you are, because that is not a BMR calculator (it's probably a TDEE calculator, which we'll get into next).
Suppose your BMR is 1500 (it'll be higher if you weigh more, since your body spends more energy so that it can maintain a larger system). If you're short and thin, it'll be lower. Anyway, if your BMR is 1500 calories, it means doing absolutely nothing, you burn 1500 calories in the day! Good deal. Something for nothing!
But we usually don't do absolutely NOTHING. Even if you sit on the couch all day playing video games or reading, maybe getting up a few times to use the bathroom or pay the pizza man, you burn more calories than your BMR. How many more? Well, if you're idle, you probably burn roughly 1.2 x your BMR. So if your BMR is 1500 calories, you realistically burn 1800 at a minimum, just lounging around the house, or doing office work at the computer.
Where'd that 1.2 come from? It's sometimes referred to as the "sedentary TDEE coefficient". It just happens to be a number, that when multiplied by your BMR produces the number of calories roughly equal to the Total Daily Energy Expenditure (TDEE) of a sedentary individual. So, while 1500 is your BMR (in this example), you can consider 1800 the number of calories you burn in a typical day without exercise. People who have a job that involves standing all day might use 1.3 as their coefficient, and people who stand and walk all day might use 1.4 or higher. If you're trying to lose weight, it's good to be conservative and use 1.2.
Continuing with our example: 1800 is your total daily energy expenditure (TDEE) on days you don't exercise. If you exercise, you need to add those calories burned to get your TDEE for that day. To figure out calories expended during exercise, google for online calculators, or consider buying a heart rate monitor. Let's add exercise to our example. If you have an average frame size and body weight, you might burn about 100 calories per mile jogging. Suppose you run 3 miles. That's 300 calories burned.
- BMR x 1.2 = 1800 cal
- jogging = 300 cal
- total = 2100 calories burned!
So our sedentary 1500-BMR individual that burns 1800 calories on her off days burns 2100 calories on her jogging days.
What's the opposite of burning calories? EATING.
If our jogger ate 1500 calories, her net calories would be -600 on a jogging day (a deficit of 600 calories) or -300 on a rest day. Why?
Think of the food you eat as an energy gain. The calories are positive. Think of exercise and your BMR as energy expenditure, so the calories are negative.
- Jogger eats 1500 calories.
- Jogger survives one day. This takes 1800 away from 1500, leaving -300
- On a jogging day, we burn an extra 300 calories, taking us down to -600. On a rest day, the jogger stays at -300.
Negative calories you say? How does that work? Well, if your car runs out of gas it has to stop. But if you run out of gas (food), you don't stop! Your body switches to the reserve fuel tanks... your body fat! So every calorie that you burn beyond the calories you take in has to come from somewhere, and your fat answers that call.
Expert note: It's a little more complicated than that. If you train really really hard, and work up a wicked deficit of, say, 2000 calories, your body may not be able to mobilize enough fat to fit the bill, and you might burn muscle in addition to fat. The fatter you are, the more fat you can mobilize. Skinny people get diminishing returns in their fat loss, so you see guys with a 4-pack working their asses off to get it down to a 6-pack.
If you jog every day, that's a deficit of 4200 at the end of the week (in our example). A pound of fat is about 3500 calories, so with a deficit of 4200 calories, you've lost 1.2 lbs (4200/3500) at the end of the week. Not bad, but you can do better!
If you could maintain a deficit of 1000 calories per day, you'd have a deficit of 7000 at the end of the week, which would result in 2 lbs of weight loss. If our 1500-BMR individual NEVER EXERCISED, and went solely by her initial TDEE of 1800, she could only eat 800 calories to have a deficit of 1000 per day. That just isn't enough food for most people. You'll find a lot of guidelines out there; a popular minimum is 1000 calories. Try to eat at least that much, and use exercise to build up a nice deficit.
Your net calories should be a negative number if you want to lose weight. It should be positive if you want to gain weight. To calculate it, start with the calories you ate on a given day, perhaps 1500. Subtract your BMR x 1.2. Subtract your exercise calories. The number you are left with is your net calories. If you want to lose weight, you need to track this number! Make yourself a spreadsheet and enjoy being a little hungry =D
If you want to be 100% sure you lose weight, count every single calorie that you put into your face. EVERY SINGLE ONE. If you don't know the exact caloric value of the food, you don't get to eat it. If you decide to estimate, you might lose weight, you might not. I don't think it's worth the risk. A diet is hard work. In my opinion, if you don't do it right, don't bother.