This is a new and sexy media catch-phrase created to sell a new load of books and diets to those still looking for a silver bullet. What does it really mean? “Vegetarian”.
Broadly, it can mean anything from including more vegetables on your plate to a completely vegan lifestyle to virtuous-sounding products like “plant-based milk or plant-based protein powder. Beware of any program selling a lifestyle or product delivering “complete or perfect health” (here’s an example of someone trying to sell you something you already know). As always, nothing is black and white, and you have to use your judgement instead of taking things at face-value. If it sounds like snake oil (as opposed to fish oil, see below) its probably an expensive unsubstantiated hoax.
At it’s most innocuous and helpful, anything “plant-based” would be something that leans towards less meat and more vegetables. It’s based on the premise that resources (land, water, time) would be more efficiently used to create large-scale vegetarian crops than similarly-sized animal operations. Also, a more vegetarian, or plant-based diet is likely healthier, as long as the plants you are eating are green leafy vegetables and fresh fruit. The catch phrase could equally describe french fries and danishes (because wheat and corn are plants, right?)
For me, the take-away here is beware of re-packaged shiny new catch-phrases that you already know. They are simply designed to sell you things. Buy and eat a variety of local and fresh food, mostly vegetables and you’ll be fine.