I get a lot of nutritional questions: from friends of all athletic calibers, from couch potato to potential Olympic Trials qualifier, from my family, and from people who I know less well (read: random people in Whole Foods or at the start of races).
Let me preface this first qualify this post with the bit of information that I've been a vegetarian for mostly non-health reasons for almost half my life at this point. I'm not a proselytizing vegetarian, so I will never post something that intends to tell anyone they should never eat meat. I don't think I am the healthiest person I can be eating as I do now (as opposed to the optimal way I could eat if I incorporated some amount of meat into my diet). In general, the fewer absolute constraints a person has, the easier it is to find an "optimal" diet within those constraints. That being said, I think most Americans, and Westerners in general, would be healthier eating less meat than they do. But that's a tangent for another post.
I was prompted to write this post when a running friend asked a number of the marathoning Hounds how they would carbo-load for a big race, and fuel during the race, if they were on the Paleo diet. The so-called "Paleo diet", or Caveman diet, suggests that humans ate mostly meat and vegetables until quite recently in our evolutionary history. Grains, legumes, dairy, and anything at all processed are considered relative newcomers to the human diet, or at the least, hard for us to digest. I'm far from an expert on the paleo diet, but as I understand it, followers are supposed to eat mostly meat and vegetables, some limited amount of starchy vegetables (such as sweet potatos), a small amount of fruit, and little or no simple sugars, grain, or dairy. There are several parts of this diet that are worth discussing, both on the merits and drawbacks, for normal people as well as athletes. In particular, here are my opinions on removing grains, legumes, simple sugars, and dairy, restricting the intake of fruit, and eating a lot of vegetables and meat.
I will talk about this in terms of 3 people: Joe, who's a normal, relatively sedentary person who doesn't exercise that much and has a job sitting at his desk, and would like to lose some weight, Susie, who's a serious competitive athlete, and Sam, who has recently started exercising but isn't trying to win races or compete at the limits of her physical abilities.
First, let's talk about the removal of grains from the diet. Joe, who sits at his desk and doesn't exercise, could definitely find that restricting his intake of grain makes losing weight easier, though may feel sluggish if all grains are removed. If Susie the Serious Athlete decided to cut all the grains from her diet, she would probably find that her energy reserves aren't replenished well when she wants to go do a hard track workout or long run. Sam might experience something in between: if Sam got a lot of her calories from grains, and cut them all out, she might lose some weight, but might find it difficult to continue going to the gym and working out.
All of these effects stem from the same source. Grains are calorically dense, and our bodies are very good at getting a lot of energy out of them. Specifically, for every gram of carbohydrate (of which grains are mostly composed), our bodies can extract 7 calories of energy to use or store. It's easy to over-eat some grains, because the grains and their byproducts have a lot of calories in small volume, and since our stomaches determine our fullness as a function of volume, dense things trick our bodies into thinking we haven't eaten as many calories as the equivalent number of calories from lighter, less dense foods. So, Joe might lose some weight from cutting out grains because he might reduce the number of calories in his whole diet by cutting out grain. Susie, on the other hand, who needs those calories for her body to replenish the glycogen stores in her muscles before and after each hard workout, would have a difficult time making it through her hard workouts. Moreover, our bodies store calories from carbs as glycogen much more efficiently than from other sources, so even if Susie ate the same number of calories from other sources such as fat or protein, her muscles would still not have the same glycogen stores as if she ate grain. That particular statement is one which is contentious: proponents of the Paleo diet suggest that our bodies become more efficient at burning fat and protein, and storing glycogen from starchy carb sources, such as potatoes. One thing is uncontentious: most elite endurance athletes do not remove grains from their diets entirely, and given how far endurance athletics has moved towards the scientific, I'd like to believe there's at least anecdotal evidence to support my claim. Sam has some combination of these effects: she may eat fewer calories but find she's not as energized for her workouts as she was when she ate some grain.
Let's talk the removal of legumes. This is a particularly sticky point for me: as a vegetarian, and a bit of a health lentil, I have a pretty hard time understanding what's so wrong with legumes: even for people who are trying to reduce their carbohydrate count, legumes are full of fiber and protein as well as the carbohydrates they carry: a cup of them cooked often contains only 100-200 calories, and keeps a person much fuller than that volume of, say, vegetables, because our bodies take longer to process fiber and protein. They are difficult to digest, because of all of their fiber, which is part of the reason Paleos cut them out. Anyway, particularly, Joe, Sam, and Susie would probably all be healthier, both in terms of their digestive tracts and cholesterol levels, if they got more of their protein from legumes. That being said, I don't know that there are any particular negative side effects these people would notice by cutting out legumes(unlike grains, if they were getting enough protein and fiber from their meat and veggies).
Simple sugars act in some ways like grain in this hierarchy Joe would probably lose weight if he cut out all the simple sugars from his diet (they don't have much useful for inactive people: calories without vitamins, or fiber, or protein). Sam would probably have little or no difficulty exercising even if she cut out her simple sugars, and might lose some weight to boot, assuming she was still getting a reasonable amount of carbohydrates from grains or other sources. Susie is a somewhat different story. During hard workouts and races, Susie often depends on maltodextrin (derived from corn), or Gatorade, or other simple sugars, to refuel. These are the most readily available sources of energy during exercise: assuming our bodies are going to burn through our glycogen reserves during an activity, it is easiest for it to keep burning simple sugars as a replenishment. Without these sources of fast energy, Susie will probably have some trouble fueling during all-out effort events. Even when she is not racing, Susie may have trouble replenishing her glycogen, depending upon whether or not she is able to get as many carbohydrates from other sources (which is of particular worry if she is also not eating grains).
Restricting or removing dairy is, in some ways, the part of the paleo diet regarding which I am most agnostic, scientifically speaking. Some people have difficulty digesting dairy, so there's that. Other than calcium (which is found aplenty in greens that you should be eating in excess if you're paleo), there isn't much in dairy which will be hard to replace with meat. Specifically, protein deficiency is not a worry I would have for anyone following the paleo diet.
For any of the three test subjects, Joe, Susie, and Sam, they would almost be uniformly healthier if they ate more non-starchy vegetables. My mantra, when it comes to veggies, is "more is better! So long as you vary what kind of veggies you're eating somewhat" (this caveat comes from turning myself orange in college from eating too many carrots, and there is some folk lore of a woman dying after OD-ing on kale). Vegetables have fiber aplenty, some carbohydrates, lots and lots of water, and are delicious. Eat them. All the time.
The final part of the paleo diet I've yet to discuss is that of eating a bunch of low-fat meat. I guess, if you've restricted all of the simple sugars and bad sources of fat (high-fat dairy and processed food), low-fat meat won't be a huge problem in terms of fat or cholesterol, but less lean meats would be. Moreover, protein is a must, and if grains and legumes are cut out, meat and veggies are the last opportunities to get protein into a person's diet. That being said, I definitely quesiton the nutritional merits of eating so much meat. Certain cancers are found in much higher frequencies in groups that consume more meat, especially red meat. If the meat you're eating is treated with hormones or antibiotics, you'll be getting extra doses of those with eating so much meat. If a majority of your calories are coming from meat, there is a distinct possibility that you'll be eating *too much* protein, which can tax your kidneys, which have the task of removing excess protein from our bodies. This critique completely ignores two other reasons one shouldn't get most of their calories from meat: eating too much meat is environmentally irresponsible and expensive.
All in all, each of these pieces of the Paleo diet have certain drawbacks and benefits, some of which are more pronounced for sedentary or active people. I definitely think (and am backed up by Science) that reducing the amount of simple sugars, refined carbs, junk fats, and processed food in general would be beneficial for any person's health. But, making the restrictions of the Paleo diet seem somewhat artificial. Whole grains and legumes are almost certainly good for anyone, and too much meat is almost certainly bad for anyone. The problem I have with the Paleo diet is that it completely avoids what I think is the most basic part of nutrition: balance. Carbohydrates aren't inherently evil. They give us energy and a whole slough of B vitamins that are necessary for performing basic tasks as well as running marathons. A person might lose weight by removing all of the carbohydrates from their diet, but that is a function of calorie restriction more than anything else. If, instead of cutting out all carbohydrates, a person tried to cut out processed food, like white flours, simple sugars, hydrogenated fats, and anything that comes in a package, and tried to eat a bunch of vegetables, whole grains, legumes low-fat dairy and meat, they would likely find they would also lose weight, for the same reason: eating unprocessed food has more fiber which fills a person up with fewer calories. The less-processed diet doesn't ignore a very valuable source of energy that humans have been using for fuel for thousands of years, it just finds them in healthier forms than from bleached white flours or simple white granulated sugar.
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