Big Eater: Of course, this depends greatly on species, which in fairness doesn’t count, because it applies equally to everyone of that species. It does apply – in its “thin kind” form, mostly – to most transsophonts, though, simply because none of their modifications repeals the law of conservation of energy, and so that energy has to come from somewhere…
To work an example, the caloric requirements for an average eldrae baseline, before extensive transsophontism set in, were around 3,500 kcal/day (contrast with the human requirement of the order of 2,250 kcal/day; powering various capabilities the Precursors found desirable already made their metabolisms run fairly hot). By the time you count in the modifications included in the modern alpha baseline, that’s roughly been doubled (i.e., around 7,000 kcal/day), although food intake hasn’t increased that much because of efficiency improvements made to the digestive system, including the ability to digest quite a healthy portion of the cellulose included in the diet. So, yes, rich food and plenty of it, eaten heartily, is the rule of the day!
Additional enhancements, like, say, all the military-grade combat add-ons, of course, only increase the effect. And also, that’s base rate, before exercise, etc., are taken into consideration. I have not yet addressed what MREs are made of in this universe, but if I turned out to be a big steak with buttery mashed potatoes and a sherry trifle chaser, it would not surprise me one bit.
(Also, yes, there are people who have noticed this – really fairly obvious – effect and so tap the secondary market created by selling artificial immune systems, etc., as calorie-consuming slimming aids. Of course there are.)