There is good evidence to suggest that a predominantly plant-based diet is healthier than other diets such as low fat, low carb, keto diets or diets with higher meat content (esp. red meat). In fact, the Mediterranean diet (which is largely plant-based) has a tremendous amount of evidence show it is effective in reducing the risk of cardiovascular disease, promoting weight loss and combatting insulin resistance and diabetes. Diets low in fibre and high in red meat content in particular have been linked to higher rates of colorectal cancer and cardiovascular disease.
You can find out more about the Mediterranean diet here:https://www.racgp.org.au/