But what would they eat instead? Non-starchy veggies by their nature provide little energy, so what? In even a best case scenario avoiding the obvious cheap processed carbs/industrial seed oils and eating whole foods, plant protein value is lesser so more is needed plus comes with a big dose of carbs in legumes, grains, nuts etc., not a friendly eating pattern for those with metabolic issues. Not to mention the lectins and other anti-nutrients provided by plants to discourage animal life from consuming them and their seed "babies." And as others have said, aging people need more, not less, high quality protein to avoid muscle wasting and frailty.