For all its popularity, it's doubtful whether the Paleo Diet is really even possible in our day and age. According to Stanley Boyd Eaton, who, along with colleague Melvin Konner, originally wrote about "Paleolithic Nutrition" in a New England Journal of Medicine article, Paleolithic people "ate about three times as many fruits and vegetables as modern humans do." And, when they did get a hold of meat, it would've been now-widely-unavailable creatures like mammoths, not today's farmed chickens and cows, penned up and eating biologically-bizarre things. (Mammoth has occasionally been on the menu, when a carcass gets dug up, but even Paleolithic people might have turned their noses up at 250,000-year-old steaks.) Supposing we all upped our fruit and vegetable intake--the planet still could no longer support everyone eating a diet centered around meat. Which means, unless you're relatively rich and somewhat delusional, historic Paleo is off the table.
So if we can't go for a 10,000-year-old diet, would something more in the 500-year range be possible? Or at all beneficial? Well, it turns out life expectancy in the Tudor era (say 1485-1603 A.D.) wasn't any great shakes. On average, you were looking at your mid-30s, a little less if you were a woman, since childbirth was so perilous, but really if you made it through childhood you had a good chance of living longer. It was the high infant mortality that dragged overall life expectancy way down. In any case, though, few made it to old age. Accidents or disease dragged them off, since once you were sick you were basically a goner, however many times the local doctor might "bleed" you to be helpful.
On the plus side, food was local and unprocessed and low in sugar, so, even if you had a long enough life to develop metabolic syndrome, you usually didn't. Only the very rich, with access to lots of sugar and delicacies, suffered from gout or even tooth decay. (Henry VIII became famously enormous and unhealthy, and even Elizabeth I was reported to have blackened, rotting teeth.) So what did Shakespearean-era people eat? According to How to Be a Tudor by Ruth Goodman, the common folk ate a lot of bread. But not bread like we know it.
Depending on where you lived in the country, your life might contain different combinations of grains. Bread made entirely from wheat was called "manchet bread" and was reserved for special occasions. The rest of the time your wheat would be mixed with rye or barley or oats or even acorn meal. But even manchet bread wasn't exactly equivalent to our modern loaves because Tudor wheat was not modern wheat.
Enormous genetic changes have occurred in varieties of bread wheat over the past 400 years, affecting the look, the yield and the nutritional make-up of the plants. Modern varieties of wheat are knee-high when fully grown, and the uniform grain-bearing stalks are tightly packed together in the field, each ear holding a dense cluster of up to fifty fat grains with plenty of gluten inside to give that soft, light, springy texture to bread that we have come to expect. (p.126)
But Tudor wheat? The author examines wheat found in thatched roofs and finds "short ears and long ones, hairy and smooth ones, red, white and grey ones, some which resemble spelt or emmer or rivet" (p.127) And the different varieties yielded different kinds of bread; for example, grey wheat "was often used for second-best bread, known as 'cheat bread.'" Not only was the wheat different, the yeasts and milling and kneading and baking techniques were different.
So what do they all taste like, these different grains, leavens, and bakes? In general they are good. The flavours are much stronger than most modern, commercially produced breads, which can be a little disconcerting to those accustomed to bland neutral flavours in their white loaf. Even the lightest, whitest of manchet breads is heavier, nuttier, denser and more filling than most of us are used to, and the commoner maslin and dredge breads are solid indeed by modern standards. (p141)
All of which means, if you decide to go on the Shakespearean diet, you're going to need to special order the heirloom wheats, mill it on stones, catch some yeast, and build your own bake oven. On the plus side, that chewier bread will strengthen your jaw muscles, which atrophy with age and disuse.
In addition to bread, the Tudor folk ate plenty of "pottage," or seasonal stew. Think pease porridge hot, pease porridge cold. You started with stock, added any meat or fish you had, thickened it with grain or pulses, jazzed it up with herbs, and added vegetables near the end. These stews live on in modern cooking, though we don't pay much attention to the seasons anymore.
If you were better off, you enjoyed open-roasted meats and imported ingredients, but in general, the masses were plagued by malnutrition diseases: rickets, scurvy, and anemia. The downside to local food, of course, being when local crops get hit hard. The rich would get by, as they always do, but if you didn't own land and couldn't make up calorie losses by hunting and fishing from your stocks, times were tough.
Maybe any historical diet takes a misleading view of history. After all, no one pictures themselves as the penniless beggars in period dramas, only as the well-to-do in their lovely outfits. So if I were to write a Shakespeare Diet book, I'd focus on the local, fresh, seasonal, genetically-varied food, with limited sugar and processing and--oh, wait--that diet book's been written a hundred times already.
I guess some things never change.