Plenty of folks want to “lose weight.” Ten pounds, twenty pounds, fifty pounds, a hundred pounds. One person does tons of cardio, another does tons of weight training, while a third does a ton of both.
But what do these folks have in common? Whether they know it or not, they will all lose weight the exact same way: the level of caloric expenditure will exceed the level of caloric intake. In exercise science, this is known as the Law of Thermogenics.
One thing that most people don’t realize is that every person’s body is burning calories just by living. That’s right; maintaining the myriad functions of your body requires the expenditure of energy, and what is fat or muscle, or any body tissue, but stored energy?
“So if I just sit around all day, doing nothing,” someone might say, “eventually my bodyfat will burn itself!”
I’m afraid not. The amount of stored energy your body burns to maintain itself has a limit; only exercising to push beyond that limit can burn more.
How do we determine this supposed limit, and then how do we go beyond it? Well, since fitness professionals like having a name for everything, we gave a name to this too: Basal Metabolic Rate, or BMR. This is the amount of calories your body burns at rest, just by living.
BMR is determined by a mathematical formula. There are numerous websites such this one that allow you to type in some basic information and get a decently accurate reading of what your BMR is.
Now, how do we increase our BMR? By building muscle. Muscle, or lean mass, requires more energy (read: calories) to maintain than fat. Therefore, all things being equal, if your level of lean mass increases, eventually your level of bodyfat will decrease.
This is a somewhat longer-term strategy for healthy weight loss and depends on a few different factors. But what if we want to lose weight in the short- or medium-term, while perhaps also building some lean mass? “I know how!” some will say. “Just eat fewer calories than your BMR, right?!?!”
NO! This can result in your metabolism slowing and your body entering “starvation mode,” wherein, believing actual starvation is imminent, your body stores the calories you do ingest as fat, possibly even breaking down muscle tissue to feed its protein needs. Which is not good.
In order to avoid this costly fate, there is another number we must ascertain and understand. This number is your Total Daily Energy Expenditure, or TDEE. This is the amount of calories that your body requires, and consumes, each day to maintain your weight at your current activity level.
Let’s say you are female, 25 years of age, 5 feet 7 inches tall, and weigh 165 pounds. You spend most of your day seated at a desk, but you also walk from here to there, climb stairs, prepare and eat food, fidget, talk, laugh, and other activities, all of which require the expenditure of energy.
You would have a TDEE of around 1,831 calories per day.
Therefore, if your immediate goal is to lose weight, the key is to achieve a net caloric intake of less than 1,831 calories per day.
There are actually two ways to reduce your net intake. The first is, of course, to eat fewer calories per day. The second is to more burn calories per day.
So if you consume fewer calories than your TDEE, while maintaining the same or greater activity level, voila! You will start to lose weight, because your net intake (calories consumed - calories burned) will no longer be sufficient to maintain your current bodyweight.
Now, I would be remiss if I didn’t mention a few caveats that come with this type of dieting.
One issue is that it can be hard to ascertain exactly how many calories are burned during exercise. As described here, here, and here, exercise machines are often inaccurate or misleading in this department.
Additionally, diets dependent on a substantial caloric deficit plus increased physical activity are, by definition, hard to stick to. You are demanding more work from your body while simultaneously giving it less fuel, which can easily lead to “falling off” the fitness or nutrition regimen in one area or another.
This highlights the issue of weight loss as a goal versus health as a goal.
We’ve all heard that "abs are made in the kitchen" or that “dieting is 80% of weight loss." But, in the opinion of this author, nutrition is 50% of health, and exercise is the other 50%.
If you pay too much attention to exercise and not enough to good nutrition (meaning eating both healthily and sufficiently), your weight loss becomes much harder to maintain. Every workout session becomes all about undoing the damage you did by eating unhealthily.
If your weight loss depends too much on calorie reduction in the hope of seeing faster results, it is easy to feel weak and low-energy because you are highly calorie-deprived, perhaps even eating below your BMR. On top of that, if you’re not demanding more energy from your body by exercising more, you’ll have even less energy in general. Your metabolism will slow because you’re eating less, making it harder to lose weight.
And if that wasn’t enough, even if the fat starts to burn off, it is harder to see results because there is no muscle tone beneath the layer of fat.
This is why short-term weight loss goals can be so difficult to reach and maintain: they lend themselves more to imbalances between fitness and nutrition.
On the other hand, longer-term health goals---that seek to increase lean mass and BMR while maintaining a healthy intake of nutrient-rich fuel for exercise and recovery at or even slightly above your TDEE---represent a more even-handed approach. Such goals are concerned less with scale weight and more with consistency, feeling healthy, and overall positive habit-building.
Bottom line: If you need to lose weight fast, calculate your BMR and TDEE and aim for a net caloric intake that falls somewhere between these two numbers. Lower your intake gradually and stick to your cardio regiment. And get ready to work hard, try again, strive, and succeed.
But if you have the time, willingness, and patience to change your life, take a longer term strategy. PUSH yourself doing exercises you enjoy that build lean mass and increase your BMR. Make your fitness and nutrient-rich nutrition interdependent on one another. Work at building overall discipline, using root-cause analysis to eliminate bad habits and sustain good ones, one habit at a time. Develop patience, and see long-lasting results.
And all without having to go hungry.