Assuming you genuinely are trying to make a good faith argument (which I strongly feel you're not):

Pandas eat bamboo. Bamboo has practically no nutritional value so, no, Pandas are not very energetic.

None of the vegetarians I know need 16 hours of sleep per day, and I suspect that's because

- They are not bears, and so do not have the metabolism of bears.

- They don't subsist entirely off bamboo, or one foodstuff in general.

Besides, the a primarily vegetarian diet doesn't necessarily mean no meat, it just means realising that meat production is so absurdly energy, land, and water intensive that eating it on a daily basis is simply unsustainable.

The amount of energy that goes into cooking hour meat is negligible compared to the amount of energy needed to produce it in the first place.