Its a tricky question since it depends on the person, food types/quality/quantity and nutrition.
Both someone eating just lettuce or someone just eating chicken, very soon both will see an hospital! If you see where I’m getting to.
I’m not vegetarian or vegan. My partner is a strict vegan (seen her go hungry because of E numbers!!) and we’ve been together for 7 years.
We mostly eat the same meals; bar the obvious substitutions e.g. meat for soya/tofu subs.
Partner’s diet is mostly balanced but lacks B complex vitamins (we’re aware of linseed and the like…) in particular B12 although thus far no health problems probably thanks to the occasional supplement – and this is why I’d never be vegan by choice, in this scenario, for me eggs are a must. Though I don’t believe in it, I trialed a vegan diet (or nearly.. since soya milk/spread doesn’t agree with my palate so carried on with dairy milk and butter) for around 2 months so I’d get to ‘know’ more about it. Still, each to their own.
Energy-wise I was no more or less energetic, but then it was only a short trial.
Some people, unavoidably, spoken about their cravings and how it affects weight. And that is a concern because it suggests an unbalanced diet. Though a simple equation(bar medical issues!) it causes many headaches:
Weight of (Kcals in – KCals out) + previous weight – current weight = 0.
Health also has its own equation but rather complex mathematically 🙂 Its simple to say just mix as many different types of foods as you can in any week/month, taking in roughly 1/3 carbs (broadly speaking.. e.g. potatoes, pasta, rice)+ 1/3 proteins (meat and/or pulses) + 1/3 vegetables (includes anything else e.g. fruit).
For me personally, eating is simply something I do to live and enjoy. So far, some exercise plus 4 meals a day, little rubbish, fresh, variety and insisting in good quality foods have worked for me (thank you mum and dad!) and given me the energy I need.