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Anthony Colpo (http://anthonycolpo.com/), om vilken jag inte tycker så mycket, men det hindrar ju inte att han ibland säger något intressant.

Just How Many Calories Do Muscles Really Burn?

Some commentators enthusiastically point out that muscle burns over twice as many calories as adipose tissue, the inference being that dropping body fat and adding muscle will markedly boost your daily calorie burn. In their best-selling book Protein Power, Drs Michael and Mary Dan Eades excitedly gush: “Each pound of muscle mass you pack on becomes a fat-burning dynamo, allowing you to increase your food intake without fear of fat gain.”[1]
If only it were that simple!

Before you embrace such extravagant claims, let’s take a look at the hard figures.

The resting metabolic rate of adipose tissue is 4.5 calories per kilogram, per day. For a hypothetical 75 kilogram male carrying 20 percent body fat, this means that 68 calories a day will be burnt by his body fat. The resting metabolic rate of skeletal muscle (the kind built by weight training) is 13 calories per kilogram, per day. At 20 percent body fat, our hypothetical male will typically carry 40 percent of his body mass as skeletal muscle. For a 75-kilogram man, this amounts to a daily calorie burn of 390 calories. Skeletal muscle, although it accounts for around 40 percent of body mass in an average, non-obese person, only accounts for around 20-25 percent of the body's resting energy expenditure[2].

So what accounts for most of our resting energy expenditure? The answer is our vital organs. While they constitute only five to 6 percent of total body mass, organs such as liver, kidneys, heart, and brain are voracious energy consumers and account for around 60 percent of our resting metabolic rate. The heart and kidneys are especially active, burning around 440 calories per kilogram, per day. The brain and liver, meanwhile, have respective daily energy expenditures of 240 and 200 calories per kilogram[2]. When you read that increased lean mass is directly associated with increased resting energy expenditure, you are reading the truth. What many people fail to understand, however, is that the increased calorie burn associated with greater lean mass is derived primarily from highly active organs, not from skeletal muscle.

In Section 2 of this book, you'll learn how to kick start weight loss by creating daily energy deficits of at least 400 calories. Any less than this, and weight loss will occur so slowly you'll hardly notice. This in turn, will do little to maintain the motivation so crucial for achieving your weight loss goals.

To achieve our minimum calorie deficit of 400 calories per day, our hypothetical 75kg male with 20 percent body fat would have to add a whopping 31 kilograms (68 pounds) of pure muscle tissue! While outlandish claims for huge muscle gains are standard fare in bodybuilding magazine advertisements, the truth is that only a small portion of those who take up weight training ever build over 30 kilograms of solid muscle. Even fewer achieve such spectacular gains without the use of anabolic steroids, and fewer again maintain these gains once they cease using these drugs. The few who do achieve such large increases in muscle mass naturally do so thanks to accommodating genetics and years of dedicated training aimed specifically at muscular hypertrophy.

The “add muscle, boost your metabolism” paradigm becomes even more unlikely when we consider that overweight people typically need to shed a significant amount of fat, and this fat mass will almost always outweigh any muscle mass gained through weight training. If these people successfully lose their excess body fat, then they will invariably end up with a lower bodyweight, even if they do add several kilograms of muscle via weight training. And once they have reduced their bodyweight, their resting energy expenditure will follow suit.

Lite till.

Just what sort of declines in resting energy expenditure can one expect after losing significant amounts of weight? Swiss researchers observed that overweight women who lost an average of 14 kilograms experienced a 358-calorie drop in daily energy expenditure[7]. When we run the numbers, we quickly see that the possibility of boosting resting metabolic rate through the addition of extra muscle is an extremely unlikely proposition. To simply negate the drop in resting energy expenditure observed in the Swiss study would require one to build a whopping twenty-eight kilograms of muscle! Few men are capable of achieving such massive muscle gains; in most women not partaking of anabolic drugs, such muscle gains are all but impossible. And remember, that's just the amount of muscle required to prevent the drop in resting metabolic rate; to create a 400-calorie daily deficit would require the addition of a massive 58 kilograms (128 pounds) of muscle to one's frame!