This calculator tries to simulate the effect of food, drink and exercise on the body and shows weight change as a result of this simulation.
This calculator allows you to specify food eaten, exercise performed and at what time of the day, it then calculates the effect on body weight in small time intervals, between 15 and 60 minutes for 1 to 5 days.
At first glance this sounds like absurd overkill but actually it makes a great deal of sense. The problem with most weight loss advice is that it is very high level, "eat less, exercise more and you will lose weight" when often what is needed is detail.
How much less? What effect will a 5 mile bike ride have if I do one every day? Surely that snack doesn't really matter that much?
Once you try to answer these questions it becomes clear that the longer the calculation periods become the more that answers are hidden. Well, did that 20 minutes of exercise and that extra chocolate bar cancel each other out or not? You can't tell if you look at the day as a whole.
Currently exercise can be cycling or running along with background exercise, the walking that is part of a normal day.
Although exercise calculations have to be approximations, they are pretty detailed ones. For walking general fitness is not taken in account but it is for cycling and running. This fitness level affects the exact balance of fat and glycogen used during the exercise and the recovery load.
To get this fitness level a couple of apparently irrelevant exercise specific questions are asked, so you can be running fit but not cycling fit.
As keen cyclists may have access to a power meter which will tell them exactly +-2% or less what their power levels are they can use this number, runners don't seem to have similar tech yet so their values always have to be calculated.
For exercise purposes energy expended is based on a 25% bodily efficiency, if you need 200kc to do the exercise then you will need to eat 800kc. Again this is an average number and is in part the reason why so many sources give so many different answers to the same question.
As might be expected the calculator is a simplified version of the body and exercise, many assumptions are made, default values used and handling of special cases limited.
Some might notice that the calculator uses blood glucose and glycogen interchangeably, this is clearly inaccurate but it only has any real effects if you try to set up a scenarios that don't reflect reality just to "prove that the calculator is rubbish".
Clearly if you are an expert on human physiology then the accuracy of these simulations can be ripped apart especially when you look at short time periods, but I am optimistic that on balance the results are sufficiently close to reality that they are informative and useful.
The simulation is intended for people who are looking for a general overview on food, exercise and bodyweight rather than elite level athletes looking for a tool to use as part of a training plan or someone looking for something that is so accurate that it can be relied upon to lose weight.