Some would say however, that burning more calories than you eat would help, though I feel often changing the makeup of what someone eats, would help potentially more, assuming it's not simply a case of being sedentary that caused the gain and the diet has remained as good as it was when exercise was more prominant.
Not entirely sure though why you suggested Nuts and grains. I'm not criticising, just curious
Tracking calories is notoriously difficult anyway with electronic devices, as you'd need to use several different makes and models of the same machine(s), for several consecutive days, at the same time and with the same settings and duration, because then if a consistent group of readings came out of most of the recorded sessions, you would have a ballpark figure to use, allowing for maybe 5-10 calories either way on the different machine readings.
This wouldn't be practical, except in a controlled scientific test, as most, if indeed no Gyms, would have 5,6 or more different makes and models of treadmills for example, so using a calorie monitor on a workout machine, would be trusting to luck more than potential accuracy.
Plus the fact, as humans cannot physically see calories burning, any reading(s) off any machine(s) used, would still be a guide only and could be quite a way off an actual end result and not necessarily close.