The diet debate
The best diet is whichever one makes you healthier. Most of us wouldn't consider eating a bean burrito for every meal a good diet, but if that's the only way you find the strength to lose a lot of weight then mabye it was the best diet (for you).
I've never been terribly over weight but like most Americans I weigh more than BMI suggests I should. Over the decades I've dabbled off and on with low carb, Paleo, vegetarian, Meditteranean, etc. Generally my experience is ANY of them can work but you have to couple them with a very good exercise program. So basically, the most important thing is to get off your butt and then try to eat a little healthier than you had been.
I'm going to have to second Grenache. The best diet is the one that makes you healthier and you find fits your style. Some people need more carbs, others need more veggies, others need vitamins to help supplement. The most important thing is what's going to work best for you.
I'm a vegetarian. My digestion is great, I have a lot of energy. I feel sharp. It's kosher!
The idea that you need to eat animals in order to be healthy is a myth. I think eating animals is bad for you. Even eating a little animal flesh profoundly effects your body in ways that you can't be aware of unless you stop. Cheese is also not really good for you.
Broccoli, kale, and spinach is the constant in my diet. I love it. I love animals. I think they are a lot more like people than most would realize. Makes it weird for me.
I am not authoritarian about this though, most people I know eat animals. I don't have the faith to eat animals, they do. That is fine. I still find the idea of eating animals to be revolting on a personal level though.
I live in Texas, so needless to say, I get made fun of a lot for this too. "What did cavemen call vegetarians back in the day? Man who cannot hunt.". Stuff like that.
It doesn't bother me, I'm very happy with my diet.
The best diet is one which includes all the nutrients your body needs. One can do this by researching all the important macro and micro-nutrients and making sure they get the amount that their body needs. A good site for looking into micro-nutrient sources and daily requirements is whfoods (source 1). Simply search the food or micro-nutrient you are interested in. Macro-nutrient values are generally available on food packaging.