Smart Points

You are viewing revision 0fea191f from 2021-01-20 14:39:34 -0700. See current version and other versions

Links are to the current pages which may not exist or have changed. ID-based links may not work. Internal links have ^[@rev] links to this revision or add ?rev=0fea191f to a URL. See the help page for more information.

(with local PDF copies hosted here^[@rev]. However, I wanted to deduce the formula myself.

Methodology

WW asks for 7 pieces of information as listed below. However, it seems as only those I have in bold count.

Assumptions:

The fundamental assumption is that the calculation is linear. That is, if item A has, say, 10 points, and item B has 12, if you enter the information together, (with the exception of rounding), it should have 22 points.

I think this is a safe assumption, though as I will mention later, some numbers get a bit strange at higher values. I think this is due to a bug though.

Limitations

The biggest limitation is that the values are rounded. This essentially reduces the number of significant digits and introduces error. For example, 49 calories are 1 point and 50 are 2. Therefore, when I work out the formula, I will do two things:

The other limitation is that there is a limit to how large of a number I can use. The calories are limited to 9999 and the grams of nutrients are limited to 999. Plus, the value is limited to 999 as well. Finally, There does seem to be some bugs when using high calories with high protein (needed since protein is negative and another limitation is that you can't have negative points.

Determination

I will therefore collect many data points (at the boundaries of rounding for more accuracy) on all contributors. I will set the others to zero (except when I do protein where I will fix calories). I can then do a linear fit of the form ax+b. For all but protein, I expect b to be zero, but this may or may not be the case due to rounding. Either way, I am only interested in a

The process was made easier from my earlier investigations and from the above-linked sites. I was able to guess close to the value to start. For protein, I needed to start with some calories. I choose 8993 calories (for 273 points). This is exactly on 8992.5 --> 272.5 border so it worked well

Results:

Below are my results and those from the above-linked sources. Note that the actual values should be a coefficient (that is multiply the number of grams/calories). Instead, I am inverting it to look at whole numbers.

Source:	My Results	Weight Watcher Geek	Calorie Lab
calories/point	33.05	32.79	33.00
g. sat fat/point	3.666	3.636	3.667
g. sugar/point	8.064	8.333	8.250
g. protein/point	-10.29	-10.20	-10.31

We are all pretty close. And if you read the Calorie Lab description, I gain more and more confidence in their formula, especially when you consider their methodology and thought process. I think I will use their formula in my calculations

Alcohol

Weight Watchers does not give you the option to enter grams of alcohol. Therefore, I am left to try to determine it myself. These should be taken with a huge grain of salt as they rely on too many assumptions and unknowns.

Use 100 fl oz. This is 6414 calories and 927.4g. Note that Wolfram Alpha says 933 grams (probably based on the density of ethanol). We will go with Calorie King to at least be consistent. (But also note below what WW says)

We know from prior calculations that 6416 calories alone is 194.42 Smart points.

If we put in 100 fl. oz. Scotch into WW, we get 231 points. If we put in 1000, we get 2313. Therefore 100 fl. oz. is 231.3 points. Also note that WW says this should be 64667 calories or 6466.7 for 100 fl. oz. We will address this soon.

Difference in points is 231.3 - 194.42 == 36.88. With 927.4 grams of alcohol, that is 36.88 points/927.4 grams or 0.0398 points per gram (or 25.15 grams/point)

Using WW' calorie values, we have 100 fl. oz scotch as 6466.7 calories which we find to be 195.96 points alone. Therefore the alcohol adds 35.34 points. Again, use Calorie King's 927.4 grams of alcohol, we find 0.0381 points per gram (or 26.24 grams/point).

Discussion

We note that all servings of alcohol are approximately the same (0.40 ABV * 1.5 fl. oz = 0.60 fl oz. in scotch. 0.05 ABV * 12 fl. oz = 0.60 fl oz. in beer). Again, sticking with Calorie King, this means that there are about 14 grams of alcohol in a serving. That add about half a point. Really not as bad as it used to be.