SIAM Lifesciences '08

I've just returned from the Society of Industrial and Applied Mathematics (SIAM) Lifesciences meeting in Montreal. I haven't traveled to a meeting since my baby was born so it was nice to catch up with old friends and the field. I thought that all of the plenary talks were excellent and I commend the organizing committee for doing a great job. Particularly interesting was a public lecture given by Stuart Kauffman on his new book "Reinventing the Sacred". That talk was full of many ideas that I've been directly interested in and I'll blog about them soon.

One of the things I took away from this meeting was that the field seems more diverse than when I organized it in 2004. In particular, I thought that the first two renditions of this meeting (2002, 2004) were more like an offshoot of the very well attended SIAM dynamical systems meeting held in Snowbird, Utah on odd numbered years. Now, I think that the participation base is more diverse and in particular there is much more overlap with the systems biology community. One of the unique things about this meeting is that people interested in systems neuroscience and systems biology both attend. These two communities generally don't mix even though some of the problems and methods have similarities and would benefit from interacting. Erik De Shutter wrote a nice article recently in PLoS Computational Biology exploring this topic. I thus particularly enjoyed the fact that there were sessions that included talks on both neural and genetic/biochemical networks. In addition, there were sessions on cardiac dynamics, metabolism, tissue growth, imaging, fluid dynamics, epidemiology and many other areas. Hence, I think that this meeting does play a useful and unique role bringing together mathematicians and modelers from all fields.

I gave a talk on my work on the dynamics of human body weight change. In addition to summarizing my PLoS Computational Biology paper, I also showed that because humans have such a long time constant to achieve energy balance when on a fixed rate of energy intake (i.e. a year or more), we can tolerate a wide amount of fluctuations in our energy intake rate and still have a small variance in our body weight. This answers the "paradox" that nutritionists seem to believe, namely that if a change of as small as 20 kcals/day (a cookie is ~150 kcal) can lead to a weight change of a kilogram then how do we maintain our body weights if we consume over a million kcals a year. Part of their confusion stems from conflating average with standard deviation. Given that we only eat finite amounts of food per day then no matter what you eat in a year you will have some average body weight. The question is why the standard deviation is so small; we generally don't fluctuate by more than a few kilos per year. The answer is simply that with a long time constant, we average over fluctuations. My back of the envelope calculation shows that the coefficient of variation (standard deviation divided by mean) of body weight suppresses by a factor of 15 or more the coefficient of variation in the food intake. This also points to correlations in food intake rate leading to weight gain, as was addressed in my paper with Vipul Periwal (Periwal and Chow, AJP-EM, 291:929 (2006)).

Karen Ong, from my group, also went and presented our work on steroid mediated gene expression. She won the poster competition for undergraduate students. I'll blog about this work in the future. While I was sitting in the sessions on computational neuroscience and gene regulation, I regretted not having more people in my lab attend and present our current ideas on these and other topics.