Here’s a possible way to fill in the blanks:

We are always being told about the (1) **benefits** of regular and (1) **vigorous** physical exercise. But how often do you hear people talking about the (2) **harmful** aspects of this modern (3) **obsession** with health and fitness?

It is time people realised that exercise is an (4) **addiction**. The act of exercising releases a chemical in the brain which has the (5) **pleasurable** effect of making you feel both relaxed and (6) **energized**. It is, in fact, a drug. That is why real fitness-freaks feel the need to work out (7) **incessantly** often, and become (8) **nervous** and depressed if they’re kept away from the gym for too long. So before you sign up for a year’s (9) **membership** at your local health club, ask yourself if you are really (10) **willing** to sacrifice your freedom and self-respect for the sake of ‘fitness’.