Increasing Bedtime Volatility

Above is a time series chart of when I go to bed. The date is on the horizontal axis and on the vertical axis is the hour at which I go to bed. Zero is midnight, -1 is 11:00pm, 1 is 1:00am, and so forth.

You can see from the chart that a major change in average bedtime occurred at the beginning of February 2009. This happened because I changed jobs from working part-time during the afternoon to working 9 till 5.

Normally what happens is I wake up at 6:30 in the morning on Mondays to Fridays. However, on weekends I normally stay up late, which is what causes those spikes to appear. About a week ago I went to a sleepover, and I stayed up till 5:30 in the morning for that. This explains that major spike towards the end of the chart. As you can see, I adjusted for that by going to sleep really early the following day.

What I have only just noticed from plotting the data is that the volatility of my bedtime seems to be increasing over time. My sleep is becoming more and more erratic, which may not be good for my internal body clock.

Coffee at Work

In a previous blog post titled Frugality at Work, I claimed that being frugal made it difficult for me to behave normally at work. I have discussed this idea with friends, family, and strangers, and I have taken steps to address the issue.

I have noticed that many people at work bring their own lunch. The economic recession may the reason for this. There are some people who always eat out, and in order to still have lunch with them I normally eat my meal either before going out with them or after. When I go out to lunch with then I usually only drink a cup of coffee, usually a latte or a flat white (even though the two are quite similar). A cup of coffee costs about $2.80 to $3.00 per cup, increases my concentration, and provides lots of antioxidants. Normally my friends pay about $10 or $15 for a full meal, so I do save quite a lot of money by only drinking coffee. I prefer to just have a coffee at a cafe or restaurant instead of bringing my own lunch. The reason is because many restaurants or cafes actually do not allow you to bring in outside food.

Sometimes I wonder whether paying $2.80 per coffee is a good deal. You can easily make your own cup of coffee with your own machine or even just make instant coffee, and the overall cost is probably a few cents per cup. Nevertheless, I understand that I am paying not really for the coffee itself but for the atmosphere, the warmth, the environment, etc. It's also a great way to socialize rather than just staying at your desk and eating all by yourself. Walking to the restaurant or cafe gives you exercise and fresh air as well.

Losing Motivation to Exercise

The chart above shows how much aerobic exercise (on my exercise bike) I have actually done (in blue) and how much aerobic exercise I think I should be doing (in pink). I assume that I should be getting 30 minutes of exercise per day.

The chart shows that lately I have been doing very poorly and I no longer have an aerobic exercise surplus. Rather, I am in deficit, and I will need to do a lot of exercise to get back into the black.

The chart shows that in the early days when I started recording exercise data I did much more exercise than I should be doing. These were the exercise boom times. In fact, I used to weigh about 82 kilograms and now I have gone down to 72 kilograms. I am 1.82 meters tall, so that is a BMI fall from 24.8 to 21.8. I do not exercise to lose weight. In fact, I think that now I am a little bit on the skinny side, so weight loss is not something I consider.

The chart shows that this boom gave way to a recession at the start of 2009. I started working full time at February 2009 and my exercise picked up again but now you will notice that the lines aren't smooth anymore. The lines seem to resemble stairs. This occurs because, during full-time work, I only had time to exercise on the weekend, so instead of doing 30 minutes of exercise per day I would do about four hours on the weekend. Lately, however, my exercise has completely fallen flat. This latest exercise recession is nothing like the one I experienced at the beginning of 2009. This recession is seeing no growth in exercise duration whereas the recession at the beginning of 2009 saw exercise duration increasing very slowly.

Vitamin D Supplements

For a long time now I have been taking Cenovis multivitamin tablets. Each one of these tablets contains 200IU of vitamin D3. I have recently read that scientists are starting to believe that 200IU per day of vitamin D (the amount recommended by the U.S. government) is not enough. Many scientists now believe that 1000IU of vitamin D3 per day should be the new recommended intake.

I began recording my vitamin intake from November last year (2008). At around April of this year (2009) I started taking pure vitamin D3 supplements (Oste-Vit-D) in addition to my normal Cenovis multivitamins. Since I take both Oste-Vit-D and Cenovis multivitamins, this means I get 1200IU of vitamin D3 per day. However, because I don't always remember to take these tablets every day, I am confident my intake of vitamin D3 will average out to about 1000IU per day from now on. My graph below confirms it. It shows how much total vitamin D3 supplements I have taken since November last year.


Many people are curious to know why I take vitamin D supplements. They tell me that spending time in the sun gives enough vitamin D. Spending time in the sun can give you vitamin D, but spending time in the sun also increases the risk of skin cancer. Many people laugh at me because I have dark skin. They claim that because I have lots of melatonin in my skin that I have lower risk of getting skin cancer. That is true. However, just as dark skin reduced the probability of getting skin cancer by blocking UV rays, it also reduces the ability the body has to synthesize vitamin D from sunlight since UV rays are necessary for vitamin D synthesis. Hence skin darkness is irrelevant.

Further Reading: Skin Color Matters in the Vitamin D Debate