Just chiming in to say I've been doing well on a paleo-ish diet for 11 years. In my early 20s, I bought in to new-agey diet dogmas about the idealness of whole grains and beans and ended up eating a predominantly vegetarian diet for the next 20 years. In my late 30s, I started gaining weight, and within 5 years I had 30 pounds of subcutaneous flab drooping off my body. I ditched all the starches except for two slices of sprouted grain toast per day, ate one meat/fish/poultry/eggs meal per day, plus fruits and vegetables, and I lost 30 pounds in 5 months.
The biggest takeaway from my own life experience is that there is no one-size-fits-all diet, and that you've got to listen to your own body and figure out what works for yourself. The diets of rice-eating Asians, blubber-eating Inuit, endurance athletes, other ape species, herbivorous animals, or any other human/animal population a dietary dogmatist might point to as some kind of universal ideal for humans are simply not pointers to what I personally should eat in order to thrive ideally. I spent 20 years, ignoring my body and eating according to external dogmas, and it was a huge mistake.