Post-Fast Day 8: 318 lb BMI 45.7 Body Fat* 44.5%
Finally, my weight has stabilized after eight days of post-fast eating. The calculations I have in my spreadsheet would appear to be fairly on the money in terms of the amount of weight I was expecting to put back on after the water fast completed. I was actually hoping that I was wrong in that my estimated weight wouldn’t go this high. However, all things considered, I think the fact that I’m seeing the numbers I am below is really the best of all possible outcomes.
|Days||Nutrition||Cal/Dy||Act. Weight||% from fat||Est. WW||Est. Weight|
I’m actually thinking that I must have come fairly close with my approximations as the 16.2 lbs of water weight I was expecting to regain seemed to be fairly accurate. Considering I’ve remained on a reduced caloric nutritional plan post-fast, some additional weight loss was to be expected.
There are a couple of different things I believe can derive from the information above: a) confirmation of glycogen depletion, and b) total energy expenditure.
The first is that my assumptions about fat loss, RVCO2, and the logarithmic decline of glycogen storage and release seem to be close to my actual. In order to figure out what the estimated water weight loss was as compared to weight loss from body fat, glycogen cannot possibly decline on a linear basis. Nor should it completely be exhausted. This is all supposition, however, my thinking on the matter is as follows. Ancient man could not possibly have remained competitive for food if the body completely exhausted its glycogen storage after one day of fasting. It would make sense that the body would adapt to reserve some glycogen for some period of time, say 3 weeks based on previous studies, that if you needed extra energy for hunting you could still remain competitive. While the transition from using glycogen to using muscle or ketones would slow down, it shouldn’t necessarily shut off completely.
The formula I’m using to determine glycogen decline was based on a few general assumptions from previous studies and, to be fair, some random guesswork in fitting the logarithmic curve to some of the assumptions in those same studies. However, if the data I have above is any indication, it seems to be good enough to be able to set realistic expectations for actual versus estimated weight loss for people with BMI’s over 40. Whether it holds true for BMI’s under 40 I cannot say since my BMI is still in the 40+ range.
Estimated % of Calories from Fat = 0.8 ( LN(fast day-1) ^ 1/4 ) + 0.3
Where the estimated % of calories from fat has a maximum value of 87.5%.
This is in part based on previous studies that showed a decreasing “return” from water fasting that seems to level out in the 3rd week of fasting. Also based on the fact that adipose tissue is only 87.5% fat with the remainder being water and other tissue components.
Total Energy Expenditure
The second is figuring out what my total energy expenditure is. I’m currently in the process of switching my metabolic calculations over to favor the Mifflin-St Jeor Equation for determining the basal metabolic rate (BMR).
Men: (10 x weight in kg) + (6.25 x height in cm) – (4.92 x age) + 5
Women: (10 x weight in kg) + (6.25 x height in cm) – (4.92 x age) – 161
Total Energy Expenditure (TEE) is essentially a function of four components including the Basal Metabolic Rate (BMR), Non-Exercise Activity Thermogenesis (NEAT), Thermic Effect of Your Food (TEF), and Thermic Effect of Activity (TEA). The first three of these factors provides your total energy expenditure, not including activity. This is the number you generally want to base your caloric nutritional plan on.
Providing a thumbnail estimate of your NEAT and TEF values are typically done through knowing your BMR number. However, one of the key questions is, what mass do you use to calculate that number based upon.
If I use my current mass (145 kg) my BMR is ~2320 cal/dy
If I use my target mass (80.5 kb) my BMR is ~1820 cal/dy
A difference of 500 cal/dy!!
The second question is, what value do you use for calculating your Non-Exercise Activity Thermogenesis rate.
There doesn’t seem to be a consistent answer to this question however from what I’ve found here is a general guideline for making that determination:
|NEAT Factor||Activity Level||Non-Exercise Related Activity|
|1.1||Sedentary||250-500 cal||Fewer than 1,000 steps a day|
|1.15||Lightly Active||450-700 Cal||1,000 to 10,000 steps|
|1.20||Moderately Active||700-1000 Cal||10,000 to 20,000|
|1.25||Active||950-1400 Cal.||More than 20,000 steps|
Also, as a general rule, the Thermic Effect of Your Food (TEF) is approximately 10% (x 1.1).
So taking all this into consideration, and assuming my NEAT factor is sedentary at the moment, my TEE value could be as low as 2200 or as high as 2800. While 2320 is still in that range, that is still a big difference if I get it wrong.
However, I can see from the chart above that in the eight days since I stopped the fast, my peak weight came in at 1.7 lbs below my estimated water weight taking into account the number of calories I’ve been consuming since stopping the fast. Based on 3800 calories per pound of adipose tissue, that means I can narrow down the range of my TEE to approximately 2600 cal/day.
Simple ratio substitution can then give me my nutritional goal based on my 80.5 kg target weight (1820 x 2600 / 2320) or 2040 calories per day.
This is the number (2040) I need to base a calorie deficit on, not 2600.
To continue with my weight loss goals then, if I want to try to maintain a 20% deficit, then my nutritional plan needs to be based on 1650 calories/day with a “cheat day” every 6-8 days that does not exceed 2600 calories.
Two additional notes;
1) the “cheat day” calorie limit needs to be adjusted weekly as my weight continues to decline. While I’m not positive that 2600 calories is the right number, for now, I’m sticking to a “don’t exceed your max” policy until I can find out more information.
2) yes I’m using 3800 calories per pound of adipose tissue. 3500/3600 calories has been proven to be wrong and, based on previous articles on my blog here, the maximum estimated calorie count per pound of adipose tissue (not fat itself which is higher) is 3800. So for my calculations, I’m using this number as I feel it will more fairly represent the true challenge of weight loss.