I think the issue of site scope is broader than just drawing a line about nutrition, and has to address the definition of fitness as well.
We may not have many professional nutritionists here, but I tend to doubt we have many professional trainers, orthopedists, or physical therapists either. If this isn't the case, it would be useful for professionals in either camp to chime in to let us know that they are around.
We need to look at restricting or redefining the other side of site scope as well: this site is currently Fitness and Nutrition, not Random-Sports and Nutrition, so I don't see a problem with the emphasis on running and weightlifting, as these are core physical skills that contribute to overall fitness as well as to specific sports. I would point out that finding a core group of professionals in different sports is even less likely than doing it for just nutrition and basic training. For example, in this question about ice skatingthis question about ice skating, how many skating coaches do we have here?
So in summary, I think the site scope has be one of:
- Restrictive. No sports other than general-purpose "training" and no nutrition question except as relates to athletic performance. This primarily means weight loss and muscle gain. I think in this case we could safely change the name to just Fitness.
- Sports-oriented. All physical/sporting activities are allowed, but nutrition is restricted per #1. In this case, the site should be renamed to Sports.
- Health & wellness oriented. All nutrition and general wellness questions are on-topic. Physical activities are only on-topic as they pertain to structural or cardiovascular health. In this case, the site should be renamed to Health or Wellness. We'd need to define where the line is for medical questions. Doctors might be a group of experts we'd be recruiting.
- Broad. Accept pretty much anything that would fit under #2 or #3. Again, we'd probably want to have some policy on rejecting very personalized medical diagnosis questions.
My personal vote is for #1 because I'm concerned that we cannot be an expert-driven community with any of the other options since they are more broad. We need to define clearly in the FAQ where the line is between e.g. fitness activities and sports - I'd propose that it's a question of general applicability. Strength and endurance apply to all activities; specific sporting techniques do not.
The downside to this restriction is that it will significantly reduce the number of questions that we receive, which is something that we're already struggling with according to our Area 51 stats.
Update: during conversation, @IvoFlipse proposed the following list of topics which seems to comprise a nice compromise between #1 and #2. These are
- Structure and function of exercising muscle
- Metabolism and hormonal control
- Neural control of exercising muscle
- Energy Expenditure and fatigue
- The cardiovascular system and its control
- The respiratory system and its regulation
- Cardiorespiratory response to acute exercise
- Principles of exercise training
- Adaptations to resistance training
- Adaptations to aerobic and anaerobic training
- Exercise in hot and cold environments
- Exercise at altitude
- Training for Sport
- Body composition and nutrition for sport
- Ergogenic aids and sport
- Children and adolescents in sport and exercise
- Aging in sport and exercise
- Sex differences in sport and exercise
- Prescription of exercise for health and fitness
- Cardiovascular disease and physical activity
- Obesity, diabetes and physical activity
Note that these are essentially the index from Physiology of Sports And Exercise, and need to be paraphrased or otherwise rewritten.