What if electricity could be generated from workouts?

Being a (almost) regular gymmer for sometime now, I have come to realize one thing- people come to the gym mostly to lose weight. Mind you, this is in the Indian context. The concept of chiselled bodies is something quite new here, so its 60-70% of the people are overweight/obese. So the basic premise behind gymming for these souls is to lose weight, which in turn translates to burning calories, which implicitly means they're hitting the gym to spend energy. With obesity levels rising, more and more people are taking to various forms of exercise so that they can add those couple of years to their life.
On the other hand, we have environmentalists crying out hoarse about a global warming- which is mostly caused by excessive, mindless use of energy in its various forms- be it coal, petrol, whatever.
The way I can see this, this dichotomy is of energy spending for the sake of it (in the form of gymming) on one side of the coin; and trying your very best to save energy on the other. Add to this the looming global food crisis (which would take another year atleast to get resolved).

One way to solve this problem would be to find a way by which the energy spent by humans could be converted into electricity. For example, everytime we walk, there could be some small device which could be pasted on our clothes which could convert the energy from our body movements into electricity and store it in a battery somewhere in our shoes! Similarly, if the energy spent in lifting dumb-bells and bars could be converted to electricity. The dumb-bells could have batteries built into them which get recharged every time we use it. And then, when we put them back into their slots, the slots could act as docking stations and send the electricity to a main battery. Treadmills could have some regenerative mechanism by which the energy we spend in running could be fed back to it to make it run.
Another thing that can be done would be to consume less food. This in no way means that you should starve yourself. It only means that we should reduce wastage at every step in the food supply chain. And this should apply to everyone across the world. But at the same time, it should be voluntary, and not enforced on anyone by anyone else. This would reduce the demand on world food supplies, thereby slowing the food crisis to some extent. I feel we'd be able to reduce our carbon footprint by a large extent with some of these steps.

Random thoughts again, one might say... But who knows how far we are from all this?
The line between reality and fiction is a very thin one! And its growing thinner by the moment!!