A fitness trainer works with clients to improve their overall fitness and reach their health goals, which may include weight loss and eliminating dependence on medications. As a fitness trainer, you may work one-on-one with clients to assess their fitness level, develop a training plan, teach them the proper techniques for exercises, and monitor their progress towards their fitness objectives. You may also lead exercises classes for larger groups and provide nutritional advice to clients. Fitness trainers work with clients of all ages and skill levels.