What are the molecular mechanisms of inducing pleasure for physical exercise?

Question

It is known that pleasure of eating is one of the main cause of obesity. And from my everyday experience I can also see that some men really enjoy the exercises in gym, they can not live with out them. I can say similarly that I can not live without math and programming, time off from math and programming (and other intellectual and creative activities) and I have hard time sleeping and hard time doing my exercises in gym.

So - my question is - what are the molecular mechanisms that induces one to feel pleasure doing physical exercises? And can these molecular mechanisms be stimulated by some drugs without causing side-effects. I suppose - that pleasure from rational physical activity is quite natural and there should be drugs for those people who can not experience this pleasure in the amount required for living healthy life. So - is there research on such topic?

I made Google search "molecular mechanism of pleasure for physical exercise" but all the results is about further effects - how the physical activity keeps mood up. But I am more interested in the mechanisms, that creates desire, longing for physical exercise? Or I am something confusing: mechanisms for desire and mechanisms for reward and mechanisms of failure to experience reward? How all these things are connected?

This should be very important topic as it can give solution for many cases of obesity problems.

Maybe failure to experience direct reward from exercise is connected with some illnesses, e.g. with muscle-degenerative illnesses?

Answer 1

The human brain has a specific anatomic site called Nucleus accumbens, that is responsible for reward and reinforcement behavior. The neurotransmitter Dobutamine could be considered as a main molecular mechanism for reward behavior. You can find more information on https://en.wikipedia.org/wiki/Nucleus_accumbens.
A stimulus, e.g. eating, can be linked to a rewarding stimulus, e.g. I feel better after a pleasant meal. This way you learn, that eating makes you feel good. This is called Pavlovian-instrumental transfer. You can find more information on https://en.wikipedia.org/wiki/Pavlovian-instrumental_transfer>.
Obesity is a complex health issue. The main causes are high caloric intake and sedentary behavior.
You can find more information on drugs and side effects: https://www.niddk.nih.gov/health-information/weight-management/prescription-medications-treat-overweight-obesity