I know, you’ve been told over and over again that to lose weight you need to cut calories and do cardio until you dissolve in to a puddle of sweat. While it’s true that you can speed weight loss with cardio done at the right time and under the right conditions (see The Truth About Weight Loss Exercise) the best way to keep fat off long term is to add to your muscle mass. And this applies to both men and women, so ladies, don’t go away – this is for you too.
The secret lies in your Resting Metabolic Rate, or RMR. This is the measure of how many calories your body would burn if you stayed at rest all day. Literally, at rest. Doing nothing. Just lying there and breathing. You’d be surprised at how many calories it takes to keep your body alive. You have constant metabolic processes going on inside your body. Beyond the very broad spectrums of Catabolism (the breakdown of molecules to obtain energy) and Anabolism (the synthesis of compounds needed by the cells), there are many anabolic and catabolic processes constantly running to keep us alive. Digestion, respiration, glycolysis (glucose oxidation to obtain ATP), gluconeogenesis (glucose synthesis for use by the brain), the urea cycle (ridding the body of ammonium), and many more. Our body is a machine, and it needs to burn energy to keep running.
Cardio exercise speeds up the engine, and consequently all of these processes speed up as well, requiring more energy to meet demand, but it’s a temporary state. It lasts only as long as we keep moving. But what if there was a way to speed up the idle on our bodies’ engine? It turns out there is.
One of the biggest factors in our RMR is our skeletal muscle mass. All those muscle cells burn energy constantly just to keep functioning, even if we’re not doing anything. Without getting in to the difference between brown fat (good!) and white fat (bad), the white fat cells that make us look unshapely are largely metabolically inactive. They do burn a very small amount of energy, but it’s nowhere close to what muscle tissue burns. Meantime, muscle cells are calorie burning engines, running at least on idle all the time, even while we’re sleeping. The more muscle we have, the more energy we burn just being alive. Depending upon how much muscle mass we have, muscle cell metabolism can account for up to 40% of our RMR.
So how much extra muscle is ideal? After all, most of us have seen power lifters who, while being very strong and obviously having a very large surplus of muscle, are also carrying a great deal of fat. There’s also a lot of anecdotal evidence that a large surplus of muscle mass is very unhealthy. Over the past 20 to 30 years a number of very successful competitive bodybuilders made the news – by dying relatively young. Steroids were blamed of course, but there’s also a theory that their hearts just gave out as a result of the extra strain caused by carrying all that muscle mass. After all, does your heart really care if it has to pump blood to an extra 40 kilos of fat vs. an extra 40 of muscle? Probably not. Either way, your heart has to work extra hard.
On the other hand, most of us don’t have enough muscle. We start to lose muscle mass in our 30’s, through a process called sarcopenia. If you’re typically physically inactive you can be losing as much as 5% of your muscle mass per decade after age 30. By 60, this means you have 30% less muscle mass than you did at 30! This results in the frailty, both physically and in terms of resistance to disease and other deteriorative age-related conditions such as osteoporosis, that we associate with old age. But it’s completely unnecessary and avoidable. Regular moderate weight training can shut sarcopenia down cold, and even gradually add to our muscle mass, at least up to a certain point. For most of us, this point will be in our 50’s, as our natural testosterone (yes, that means you ladies too – you don’t have as much but you do have it) drops to the point where our body can no longer maintain our muscle mass without rigorous training and a proper diet, but even so regular resistance training will greatly slow the loss of this needed muscle mass.
So back to the question. How much extra muscle is ideal? There’s no mathematical answer to this, but most of us don’t need one, as we’re not planning on hitting the gym twice every day and dedicating the rest of our time to eating a carefully calculated muscle building diet. And that is what it takes to build excessive muscle, so the practical answer is ‘Don’t worry about it’, because unless you’re trying you’ll never gain that much muscle.
That said, despite ridiculous claims that are popular on the internet that an extra 4 kilos of muscle mass will increase your RMR by 500 calories per day (I can guarantee you from personal experience that this is not even remotely true), the real science does show us that muscle is 3x as metabolically active as fat. So, if you increased your muscle mass by 10 kilos, which is definitely attainable for most people, even women, who are willing to continue to work at it, your RMR would increase by approximately 120 calories per day. If you keep your caloric intake steady, this would translate in to losing approximately one half kilo of fat per month, without even trying. Let that add up for a year or two and you find yourself maintaining the body you want virtually effortlessly.
And there’s an even greater benefit to that extra muscle; it will make the cardio you do much more effective. It takes considerably more energy to move your body when it’s composed mostly of muscle instead of fat.
For short term fat loss, cardio will definitely speed your results, but for lifelong weight control, you can’t beat adding muscle mass.