The FastDay Forum

I'm manipulating some of the recent 5:2 Questionnaire results, mainly to check the data is sensible. Thought I would look at some of the Q's that we've discussed before.

Using some published BMI to % body fat correlations I calculated the fat mass and fat free mass reported by our contributors :-

Mean fat loss 4.1 kg, median 3.2 kg.
Mean FFM loss 1.5 kg, median 1.1 kg

Weight loss % fat - mean 72.9%, median 71.8%

If you use the mean and assume 9 cals per gram of fat and 4 cals per gram FFM the calorie equivalent of 1 lb of weight loss is 3470 cals, pretty close to the recognised value.

So we have some initial evidence that the high calorie reduction on fast days is not creating a loss of lean mass beyond that typically seen in dieters.

Interesting -- so that 3:1 ratio of FM/FFM loss is typical? I was wondering about that, trying to figure out how much FFM I should be expecting at my target weight.

I believe it's typical. http://www.tanita.com/en/supporting-research/p2/

If you are using a calculation of BF% based on BMI, I think any FM/FFM ratio is going to be the same for a given BMI distribution -- so it would be independent of the weight loss method. I don't think you can use it to compare 5:2 to other methods.

now there's a thought. Yep, you're right.

We do have a smattering of body fat measurements but not enough to do anything useful.

Do you have enough waist measurements to do something interesting?

About 20% of waist measurements missing, more so with the "before" value.

Waist reduction cm/week :

Mean 0.67
Median 0.60