Fiber: *humans cannot digest fiber, however the bacteria in the digestive system can make use of some of them as an energy source to create fatty acids; i.e. cellulose (broccoli, cauliflower, kale), pectin (apples, pears, citrus), psyllium (wheat bran)
Good Carbs v. Bad Carbs
What Really is a Low Carb Diet?
Therefore, a low-carb diet can mean something completely different to someone in their 50's who is trying to restore general health after years of metabolic damage from poor diet and little to no exercise, versus an athlete in their early 20's who is competing professionally and has no previous medical or significant health issues.
It's all relative!
***If you're not sure where you're at or where to begin, please contact a nutrition professional like myself, and check out the following resources!
The Low Carb Athlete by Ben Greenfield
The Art and Science of Low Carbohydrate Performance by Jeff Volek & Stephen Phinney