06 February 2014

Energy analysis of Rachel Frederickson's win on Biggest Loser

Congratulations to Ms. Frederickson on her Biggest Loser win, and also on her successful weight loss.  I hope that she can keep it off, and focus on health.

She lost 155 pounds. That is impressive. I was curious about what she must have had to do to get there, so here is an analysis.

As far as I can tell, the show was no more than 18 weeks long. She lost 155 pounds over 18 weeks, so she lost 8.6 pounds/week. How was this possible!? Why can't *I* lose 8.6 pounds per week? Here's what I've figured (and it's DON'T TRY THIS AT HOME).

She started at 260 pounds and went to 105 pounds. The average woman (though not an obese woman) has about 36% muscle mass (http://en.wikipedia.org/wiki/Muscle). So she lost 0.36*260 = 55.8 pounds muscle and (1 - 0.36)*260 = 99.2 pounds fat.

You can lose a pound of muscle for 600 calories, and a pound of fat for 3,500 calories (http://www.myfitnesspal.com/topics/show/153704-myth-or-fact-simple-math-3500-calories-one-pound-eat).

So she had to give up 33,480 calories for the muscle and 347,200 calories for the fat: [33,480 + 347,200]/18/7 = about 3,020 calories deficit per day.

Assume her metabolism was 2,000 calories/day (mine is around 1,800). She said she ate 1,600 calories/day. Then she had to BURN about 2,600 calories through exercise EVERY DAY for 18 weeks.

My exercise database shows that, for a 150 pound person (a number somewhere between her 260 start and 105 end), the average exercise burns 460 calories per hour.

She had to work out hard for at least 5 hours per day! When I mean hard, I mean hard. This is all she did.

I guess it's possible mathematically. Stay tuned to her story to see if she can keep it off.

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