We all know that us human beings are in reality power production plants. We consume food, and convert cabs contained in it in electric, chemical, or kinetic power. Why can't we produce our own electric power? Let's see.
Intake
The easy part is to convert our average food consumption in energy. The average person diet is measured at around 2,000 - 2,400 kCal. The simple converter gives that those calories are equal to 2,320 to 2,790 watt-hours (or about 2.32-2.79 kWh). If you take under consideration that cooking our meal takes your stove to be burning for at least one hour per day (which is at around 2-3 kWh), it is evident that a single person consumes energy only enough to cook his/her meal. This means you should be consuming only raw food - which is impossible - or you need to put a family of at least four to produce power. That's 7.45-11.15 kWh.
The bad news is that we consume a part of the energy we produce to stay alive. Let's see how this works.
Self Power Consumption
Depending on your weight, you consume power even when you sleep. For a 8-hour night sleep, you would consume 540-730 kCal. That's over a quarter of the energy you consume in your diet.
Now, if you simply are sitting doing nothing, you consume - again depending on your weight - anywhere from 95-125 kCal per hour. Multiply that with 16 (the remaining hours in a day), and you get 1,520-2,000 kCal.
At this point you have exhausted all the energy you receive with an average diet (obese people consume a lot more food than what the average diet suggests). So, in practice you consume as much food is needed to stay alive. To produce electric power, you will need to eat well.
But let's see how much you can realistically produce.
Power producing activities
If you've gone to the gym, you know the most common exercises a human being can perform; running and cycling. Both those activities may be connected to a magnetic rotor to produce electric power. Let's see.
1 hour light cycling - again depending on your weight - is consuming/producing anywhere from 255-800 kCal (that's 295-930 watt-hours). If you could keep cycling for 2 hours, you could produce some 0.6-1.9 kWh. If you push yourself, you can do that 2-hour cycling round two more times within a day. That's 1.8-5.7 kWh per day.
Light running is a bit better. You could be producing anywhere from 370-1,040 kCal (or 430-1,210 watt-hours). In 2 hours you could produce 0.9-2.4 kWh. Repeat that 3 times a day, and you get 2.7-7.2 kWh per day. Let's round that to 5kWh per day per person in average. An adult couple can be producing 300 kWh per month, working full time. If you subtract the energy that adult couple consumes, you would find that they would barely cover their household needs.
A pair of solar panels is producing 320 kWh per month, just by sitting on your roof.
