>> This seems unlikely to have escaped the author? Of course a hybrid diet would be in between, I'm just saying that the diet breakdowns they chose to present are almost certainly model diets from literature rather than arbitrarily chosen to make meat eaters look bad. It's a thesis, not PETA marketing material, there are some standards for rigor and they would have needed to cite and justify why they chose what they chose.

Why assume so much? The thesis is in the link you provided. You can easily check whether what you suppose in this comment is true or not.

>> That said, I honestly do not think that your diet suggestion is common for Americans, I rarely see people go a meal without meat.

So this "meat-based" diet is only relevant to Americans? That makes sense- but in that case, the comparison with vegetarian and vegan diets is also only relevant to Americans. i.e. it's American "meat-based" diets that are more environmentally wasteful compared to American "vegetarian" diets etc.