All posts tagged with statistics

Weight Loss - exercise is not enough

January 09, 2018 - Søren Alsbjerg Hørup

I have tracked my daily weight and exercise since 2016. The primary motivation: I wanted to loss a bit of body mass and to do so it would be beneficial to track my progress.

The secondary motivation: I want to statistically calculate if my weight loss is primary due to exercising. This was my initial hypothesis since my weight fell dramatically after I began my exercising. Alas I could not keep the fast decline after a few months, and my new hypothesis is that exercise not the primary factor for weight loss in my case.

This also makes perfect sense, since it is very easy to eat too much during the day which is near to impossible to burn in the evening with the one-two hours of spare time. What does the data say?

For each day since 2016 I have an entry of current weight (measured in the morning) + how much exercise I got for the day. Typically, this is how much I rode my training bike in the evening. My initial hypothesis was that more exercise leads to more weight loss, but not necessarily the day after, i.e. training for 60 min one does not result in weight loss the next day but a few days after.

To simplify my data-set I summed all the daily values into weekly values and converted the weight into a weight changes, i.e. the delta between the first measure weight next week minus the weight on the first day of the week. My hypothesis was that there was a negative co-variance between exercise time and weight change, i.e. negative weight change with increasing exercise time.

[caption id=“attachment_1581” align=“alignnone” width=“743”] 2018-01-09_07-39-03 Scatter plot showing the correlation[/caption]

As seen on the scatter plot, there is indeed a correlation between between exercise time (x-axis) and weight change (y-axis) and it is negative. It is far from perfect though, at does not explain that much. CORREL states that exercise time explains only 30% of the weight change, so 70% of the weight change is not explained by the data that I have collected.

Looking at the data it is clear that increasing exercise helps with weight loss. Getting 100-150 min of exercise during a week seems to be a reasonable choice to maximize weight loss. Beyond this the weight loss decreases in magnitude which I cannot explain.

Getting less than 50 min but more than 0 min of exercise every weeks clearly shows a negative weight loss trend, while getting 0 min of exercise shows a smaller weight gain.

Conclusion: it is important to exercise at-least 120 min a week while keeping in mind that exercise is not the primary factor for weight loss (only 30%).