Weight loss: Fat or Muscle?

5lb of fat versus 5lb of muscle!

If you jump on the bathroom scales and discover you’ve lost 5lbs (2.27kg), you’ll probably think yippee! But if you look at the picture on the left, you may pause to think twice.  Have you lost 5lb of fat or 5lb of muscle?

From a purely technical point of view, a 5lb weight loss is 5lb less on the scales but as you can see, muscle and fat vary massively in overall mass.  Although they both weigh the same, the fat has a far greater volume, as opposed to the muscles’s greater density, so if you lost the fat you would lose a lot more inches than the same amount of weight (5lb) lost in muscle.

If, for example, you’re a size 16 and you cut a leg off (don’t try this at home), you’d lose about 20% of your body weight but your waist, bum and chest would still be a size 16!  However, a reduction in your measurements by the same 20% would bring you much closer to a size 12.

So, apart from being slightly facetious, let’s be honest, it’s the inches lost that count more than the weight. If your clothes fit you better, your weight is immaterial (hence the title of this blog; Winning the Inch War).

To put the amount of fat in the picture into a real context;  a reduction of 5lb of fat would account for about an inch on a man’s waistline and about ½ or maybe a dress size on a woman (depending on both the shape of the dress and the woman).

5lb of fat contains nearly 18,000k/cals of energy as opposed to the muscle, which has about 3,800k/cals.  Exercise wise, it would take a run of nearly 200 miles or approx 40 hours of aerobics to burn off the fat. (If you want to do the maths, humans are only 60% efficient at using fat for fuel during aerobic activity which equals about 60k/cals of fat for every 100k/cals you burn and aerobic activity is about 600-800k/cals per hour dependent upon gender and fitness level.  Either way, it’s not a lot. You can find out why we don’t much fat for fuel during exercise by taking a look at Evolution Part 1)

Another point to consider; muscle is metabolically very active, even at rest it burns about 6 times more calories than fat.  Also, fat is actually burnt by the muscle; so the more active muscle you have, the more fat you can burn.

A healthy, not overweight woman (height 5’4”/1.6m; weight 140lbs/63kg with a BMI at only 23) would still have nearly 35lbs of fat or seven times the amount in the picture above.  This clearly demonstrates why you can’t get rid of body fat quickly; there’s simply a lot more of it than you think.

Can you lose muscle on a diet?  Well, it’s amazing what you can do if you try hard enough but it would have to be extreme to lose a lot.  However, prolonged months rather than weeks of very low calorie diets (VLCD) will cause muscle wastage, not just in mass but also in density.  I’m sure we’ve all seen pictures of emaciated anorexics and sadly, that’s only a small step from a VLCD.

One way to combat this is to include some form of resistance training (circuit, free weights, suspension training, etc) in your exercise regime as, not only will it burn plenty of calories, it’ll also develop a nice tight, toned physique,  especially in the upper body.  Excessive aerobic activity (hours of jogging, etc), whilst good for the cardiovascular system, causes greater upper body muscle loss because the lighter your upper body is, then the easier it is to carry around, making jogging more efficient.

Final Note

One thing I’ve not mentioned yet is water. 5lbs (2.27kg) of water is equal in volume to just over an average electric kettle’s worth and it’s really easy to shift water out of your system.  For example, carbs carry nearly 3 times their weight in water and an average person will carry about a total 550g in their muscles and liver; add in the water and you’ve got just over 2kg (about 5lbs) of body weight.

It would only take 2-3 days without carbs to drop this weight.  You would also lose another 2-3lbs of  fibrous intestinal bulk (fecal matter) that was passing through the system from your previous carb meals; making the first 7-8lbs  of weight lost from any severe, calorie restricted diet (less than 1,000k/cals per day) nothing but water and poo!

Therefore, all sensible weight loss regimes should focus on a proper balance of both diet and exercise,  focusing on healthy eating practices and a blend of resistance training and CV work; targeting fat loss whilst retaining as much muscle tissue as possible in order to keep your metabolism revved to the max.

Personally, I know which one I’d rather lose.

For more info (and other useful stuff) check out our Dump the Diets guide

Paul Lonsdale

Get Physical

Oct 2012

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1 Response to “Weight loss: Fat or Muscle?”


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