The point that all categories need not have the same scale of rations.
The different arms and services are below.
Army Air Defence
Corps of Signals
Army Service Corps
Army Medical Corps
Army Dental Corps
Army Ordnance Corps
Corps of EME
Remount And Veterinary Corps
Army Education Corps
Corps of Military Police
Army Postal Service
Defence Security Corps
It maybe mentioned that they perform different tasks with different physical levels in their work environment. And each have a different mental level in work environment and both factors have different levels of stress. This is further different, even if from the same arms or services because the issues mentioned are different for personnel from these same arms and services working under different climatic zones and different elevations from the Mean Sea Level!
Therefore, in exactly scientific terms the ration scales will depend on the type of work, the physical exercise done, the climate where operating, the altitude where operating.
Now, according to the International Institute for Strategic Studies, in 2010 the Indian army had a strength of 1,129,900 active personnel and 960,000 reserve personnel.
Imagine if the parameters were to be applied as per scientific to calculate the different scales of rations, what a total confusion it would lead to!
Imagine the procurement problems as also calculating the transport required to move the rations (taking into consideration the requirement in different areas, for each different arms and services, and depending on the climatic conditions and also the elevation the said different types of troops from different arms and services.
Now, imagine for some reason, some troops are redeployed for some operational reason to an area with totally different parameters to what was forecast, planned, procured and moved! How does one now, at this late stage, cater for what can become a shortfall or become surplus.
Therefore, there has to be standardisation in ration scales. However, with add ons for the High Altitude and maybe for water and ice in the deserts for troops under canvas or training.