While work does equal force times distance, the rest of Sergey's commentary is rather absurd. His calculation presumes 1 dimensional motion and forces, people don't move in one dimension first off. Secondly, carrying 100kg involves gravitational force and simply standing still with 100kg on your back will result in increased caloric consumption due to the 981N pushing down on your body and requiring muscle activation to not fall over from carrying the weight (your muscles are contracting and causing mass to move over distance). Additionally there is the calories burned from travel (100kg≈1000N 7700Cal/kg 0.000238845896627 calories/N•m, this equates to about 32.23km to burn 1kg of fat along the x-axis only) This does not account for calories burned in stabilization, calories burned due to metabolic processes such as converting ATP to and from ADP among other things, metabolic efficiency, anaerobic threshold, etc. Also, HIIT cardio and weightlifting also result in excess post-exercise oxygen consumption. Since O2 is a required for cellular respiration (anaerobic exercise doesn't excrete waste effectively until you stop working and permit the respiratory system to blow off CO2, the other other pH regulatory systems don't act fast enough to be relevant) it is the primary indicator of caloric consumption. This effectively means that while lifting weights on it's own doesn't burn as much calories during a workout, they burn more calories post workout (this doesn't count increased caloric consumption due to increased muscle mass.)
Short story: if you're trying to calculate work done based off of your estimated range of motion, you're wasting your time. While the fundamental point of Sergey's post was correct, it left out some pertinent details. As I don't really feel like getting into the physics of all of it in any deeper fashion than I already have, I'll ask that you take my word, as an engineering student, that between the lack of precision of measurement and the sheer amount of calculations required to figure it out would take time that would be better spent working out, resting, eating, or any number of things. So yes, there are formulas that you could use to figure it ou should you have sufficiently precise measurements, but the benefit of figuring it out doesn't even remotely come close to justifying the effort.