# Weight Loss: what really works, according to Mathematics!

I know when I read the New York Times this morning, I had to try it myself. They interviewed an obesity researcher who is also a mathematician, and what did he do? Invented, and made available for FREE a user interface to punch in your height/weight/activity levels now and what your ideal weight would be, and it will run a simulation and tell you how many calories you should be eating to lose the weight in any given amount of time. Most of all…and this is the dreaded consequence of diets…it will tell you how to maintain your ideal weight so in a few years time you don’t gain it all back after doing the hard work.
A quick excerpt from the article:

“One of the things the numbers have shown us is that weight change, up or down, takes a very, very long time. All diets work. But the reaction time is really slow: on the order of a year.

People don’t wait long enough to see what they are going to stabilize at. So if you drop weight and return to your old eating habits, the time it takes to crawl back to your old weight is something like three years. To help people understand this better, we’ve posted an interactive version of our model at bwsimulator.niddk.nih.gov. People can plug in their information and learn how much they’ll need to reduce their intake and increase their activity to lose. It will also give them a rough sense of how much time it will take to reach the goal. Applied mathematics in action!”

Had this article come a year earlier, I could have used this simulator to help me lose weight before I went on a diet to do just that. A year into this so called diet and I have lost 20 pounds, but I don’t think I will lose much more.  I was so excited about it that I blabbed to everyone…when things were going well. That was six months ago. Now I’m in the maintenance phase after exiting the weight loss phase, and that constantly grates on my psyche as I fret over every pound and try desperately not to slip back into old habits. Wouldn’t it be great if there were some way to plug in my numbers and see how I could maintain my weight?

Better yet, what would the weight simulator say?

The user interface…not SO intimidating!

I fired it up (after installing the correct java plug-in, which I apparently did not have) and briefly read the onscreen directions that looked something like this:

First I entered my height, weight (before diet), and clicked on “Estimate my activity level.” That button allows you to select various activities that generally characterize your daily life. I tried my best to approximate both how much physical activity I did before starting my diet/exercise routine according to their options. Then in the main section in the tab “Set your Goal weight,” I filled in all the green highlighted areas (see below). Clicking on the green box titled “Detailed” allows the option to list how you are increasing your physical activity, including which exercises (running, walking, or cycling), how often, and how long. I made sure to say I wanted to lose the weight within a year, but then specified a five year time window in the simulation (although it’s displayed in # of days), so it will show if my weight comes back. Then I pressed “Run Simulation” and played around with the graphical display.

My Results: initial weight loss followed by a long plateau…

The kicker: when I kept track of my own weight using my Wii Fit, I could view a graph of my weight over the course of a whole year, which I did. Astonishingly, my Wii graph looked just like this one. Somehow, my real life weight loss scenario and this mathematical calculator using algorithms I will never understand, came to the same conclusion about how the weight would come off me and how long it would take. If I counted calories (which I don’t) I could follow this simulator’s calorie suggestion and never gain back the weight! On a different note, as I went lower and lower with my ideal weight, it actually pops up with a warning, telling me “This simulation results in a dangerously low BMI,” whoops. Nice to know they are telling me what’s healthy and what’s not! I’ll probably keep playing with this thing and even start to re-think my weight loss goals. Everyone should check this out and play around to see how much they should be eating, or are actually eating!! In my case, it seems eating 400 additional calories a day for a year would result in a 20 pound weight gain if I went backwards. BUT: short bursts of eating that are few and far between: indulgences, that is, will not cause long term weight gain. So I don’t have to feel guilty about “cheating” by eating out for a friend’s birthday or whatnot! This is mentioned in the rest of the NY Times article, which I highly recommend. Anyway, I think this simulator is seriously cool…Props to Dr. Kevin Hall of the National Institute of Diabetes and Digestive and Kidney Diseases for making this tool free and available!