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 above, 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 size.  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.

To put the amount of fat in the picture into a real context, an overall 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).

Energy-wise, 5lb of fat equals about nearly 18,000k/cals (the muscle has about 3,800k/cals).  Exercise wise, it would take a run of nearly 200 miles or between 40-50 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. This means that for every 100 k/cals you burn, only 60 k/cals come from your fat cells.  Steady state cardio burns about 600 k/cals per hour (depending upon gender and fitness level) which works out at 360 k/cals of FAT PER HOUR.  Either way, it’s not a lot is it?

Looking back at the picture above, I know which one I’d rather lose.

Paul Lonsdale,  Get Physical

Oct 2015