Friday, March 10, 2006

DietPower Update 2

I have been using the DietPower Weight & Nutrition Manager for almost three weeks now. Here are my body stats:

Body weight: 256.5 lbs. (down from 264 lbs.)
Body Fat Percentage: 35% (down from 39%)

Here is a chart of my progress. As you can see, I have seriously plateaued. I have not lost any weight in the last week and a half. Why is this? The most obvious answer would be that I ate too much. But according to the makers of DietPower this is not supposed to be possible if I ate less than the budget allotted to me.

This would only be true however, if the budget alloted was based on an accurate measure of my metabolism. It is possible, however, that DietPower miscalculated my metabolism, especially since I am just starting out with the software. The reason for this is that your beginning metabolism is simply derived from a chart based on your gender, weight and age. This is going to be based on the average person and is probably not going to be very accurate. The beauty of DietPower is that it tracks your body changes over time to give you a more accurate picture of your metabolism. It does this by looking at the calories eaten and calories burned over the last 30 days and comparing it to the amount of weight gained or lost over those 30 days. But when you first start you will not have thirty days of data. So for the first thirty days the metabolism given by the software is based on a smaller data set and has to be taken with a certain level of skepticism.

Another source of inaccuracy is the fact that most of the initial weight lost on any diet is water weight. Glycogen stores are usually stuffed full before a diet, when the individual is in a calorie surplus situation. As a person moves into a calorie deficit the glycogen levels lower. Since glycogen is stored in water, as the glycogen is depleted the water is naturally expelled from the body. Of course when you lose water, you lose pounds. The software cannot distinguish between pounds of water loss or pounds of fat loss. This weight loss confuses the DietPower software into thinking you are rapidly losing fat and as a result your calculated metabolism is very high.

Both of these factors mean that initially it is very likely that the metabolism calculated by DietPower (and thus the resulting calorie budget) will be too high for the initial few weeks.

Here is a chart of my metabolism as calculated by DietPower and my calorie intake since starting DietPower. As you can see my metabolism (in green) has moved quite high. So this could be the reason I have stopped losing weight. But I think something else is at work here. As you can see from the chart above, my net calorie intake (blue) has been significantly below my calorie budget (purple). An alternative explanation is that my body has been building muscle. This is a common phenomena when starting a training program. Instead of seeing the scale go down, it may not budge, or it may even increase. As the muscle fibers are stressed they work to repair themselves. During this process, the muscles swell with water and as a result get heavier. Ultimately, the muscle will rebuild it self and be stronger than before. In many cases it will be larger and heavier.

I think this is the reason I have stopped losing weight because you can still see a change in body composition in my body fat measurements.

Here is a chart of my body fat percentage over time.
Now admittedly some of these changes are due to water retention issues and not changes in muscle or fat, but over a length of time the measurements should give an accurate picture of changes in muscle mass. You can see that in the last week and a half there has been a steady decrease in percent body fat. If your weight stays the same and your percent body fat decreases, that can only mean lean mass is increasing. Perhaps some of this is water, but at least some is probably new muscle.

How much muscle? Here is the formula for calculating lean mass:

Lean Mass = Total weight*(1 - Percent Body Fat)

Week 3: Weight = 256.5lbs.; 36% Body Fat = .36 --> Lean Mass = 164.2 lbs.
Week 4: Weight = 256.5lbs.; 35% Body Fat = .35 --> Lean Mass = 166.7 lbs.

These calculations show an increase in lean mass of 2.5 pounds. This of course also means a loss of 2.5 pounds of fat.

Not too shabby for just a week.

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