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I've been dieting and losing weight for around 3-4 months now and have been mainly doing cardio but still doing resistance as well. On average, I am losing 9lb a week however I got weighed today and was told my body fat has not gone down at all and still remains at 40%.

Could anyone please shed some light in why this is and how what I could do to bring my body fat down?

Update:

My diet (Same all week, apart from sundays)

Morning:
- Oats (30g) + water + Sweetener
- OR Porridge + Sweetener 

Lunch:
- Tuna / Chicken / White fish

Dinner:
- Steak / Chicken / Tuna + (Protein Shake)

No carbs, drinking nothing but water.

Trainning

Roughly, on average, 6 days a week:

Morning:

Resistance (12 reps 3 sets):
 - Butterfly curls (8kg+)
 - Smith Machine (40kg - 60kg)
 - Deadlifts (50kg)

Cardio:
 - Treadmill (walking at around 5.2 speech with intervals of 1.5 minutes at speed of 12.5 - 15.5)

Evening:

Resistance
 - (Mainly the same, chest machine, and zipper wire - Same reps / sets)

Cardio:
- More cardio at the evening, longer walk time. Aim to burn around 1k calories per day.. So 500+ in the morning and 500+ in the evening.

P.S. No measurements was taken, I was asked to stand on a machine and put my hands on this bar.

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You're going to have to tell us what you're eating and what exercise you're doing in as much detail as possible--at least several paragraphs--for us to be able to debug this. –  Dave Liepmann May 23 '13 at 19:33
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Also, please explain how the body fat is being measured. It's entirely possible the method is to blame (For example, in extremely obese people, loose skin from recent weight loss can throw off caliper measurements.) –  JohnP May 23 '13 at 19:38
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If you've really lost 108-144 lbs and are not completely shredded at this point, simple math says either the initial 40% was a very low estimate or you're 7 feet tall. –  Affe May 23 '13 at 20:52
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I just said that to reinforce that the problem is with the measurements, not you. If tracking that # is really meaningful to you it may be worthwhile to find a gym or clinic that has a hydrostatic tub and pay to get a real number over 4 mos or 6 mos or whatever. –  Affe May 23 '13 at 21:17
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@Phorce - Just a small note, you say you are not eating carbs, but the oats and the porridge are both carb sources. I also hope that you are doing this under medical supervision, as that is a very restrictive diet that can easily lend itself to deficiencies. –  JohnP May 23 '13 at 21:43
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1 Answer 1

up vote 6 down vote accepted

Ok, the last line of your post now makes it clear. The type of measurement that they are doing is called bioelectric impedance analysis (BIA). These have an error rate of anywhere from plus or minus 5% on up depending on the quality of the unit being used.

BIA can also run high or low depending on factors such as skin sweat, level of hydration, timing of your last meal, things like this.

Hydrostatic weighing (When done properly by both tester and testee) and DEXA scanning are the two best methods for determining body fat. Next up would be a 9 point or 7 point skin caliper test, again dependent on the skill of the tester. Then 3 point caliper, circumference measurement and personally I place BIA at the bottom of the heap.

BIA is good for trends over time, if you can manage to get on one at the same time in the same condition every day. Many Tanita or similar scales have the impedance built in, so you can weigh/analyze at the same time every day (Such as right out of bed).

I would not place too much stock in the unit at the gym, as long as the weight and the mirror are both giving you good feedback, keep it up!

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