Many of my friends and cohorts follow a particular diet. I find diets and the accompanying supporting evidence endlessly fascinating. People approach dietary theory with about the same fervor as… well, barefoot runners approach running without shoes.
Here’s a quick rundown of diets I occasionally see:
- The meat-heavy paleo diet,
- The fruit and veggie-heavy paleo diet
- An endless variation of the previous two that add specific foods like eggs, milk, cheese, or Spam.
- Weight lifters that consume primarily powdered protein
- Juice or other liquid-only diet
- Zone diet
- Raw food diet
- Long distance runners that eat nothing but calorie-dense processed fast food
- Inuit diet
- South Beach diet
- Nutrisystems diet
- Body for Life diet
- Atkins diet
- All fruit diet
- Jenny Craig
- Gluten-free diet
- Herbalife diet
- My diet (food is a form of recreation and I do not discriminate)
- and of course, the diet recommended by the USDA
Anyway, my Facebook friends know I’ve been discussing this in some detail. Here’s the fascinating part: many of the diets are contradictory, but have some supporting scientific evidence. The same goes with the logic of the diets. All can be spun to make logical sense. Paleo? It’s our evolutionary destiny. Vegan? We’re biologically-optimized for it. Avoid anything processed? Our rate of disease has skyrocketed in recent years. To make matters more confusing, the people prescribing to a particular dietary philosophy have some degree of success. Sometimes that success is measured by weight loss, muscle-building, running performance, or general subjective feelings of healthiness.
But what about health? Many people cite an increase in disease as a rationale supporting their particular diet. Good scientists (or skeptics) look for alternate explanations. Are cancer rates increasing because we eat too much meat? Or there’s too many pesticides in our pineapple? Or our eggs come from chickens that smoke too many menthols? Maybe.
Or maybe cancer rates are increasing because more babies survive through the first years of their life. Maybe the human gnome has a survival mechanism that culls “bad genes” in the womb and early childhood, and our advances in medical technology are allowing these individuals to survive until they succumb to cancer.
I have no idea if that explanation has any merit, but it is a plausible alternative explanation. The problem with using “science” when discussing diet is simple- almost everyone uses correlations to support their hypotheses. As we know, correlation does not equal causation, even if it seems to be a logical connection. As far as I know there are no convincing peer-reviewed meta-analyses supporting one particular dietary philosophy.
Note- a book or report about a particular diet full of correlations and logical arguments, no matter how well-written and persuasive, is not a substitute for actual peer-reviewed experimental research. This goes for diets and anything else, including my book. Yes, barefoot running is in the same class as all of the diets discussed above- it makes sense to some, but we still need to maintain a degree of skepticism. We have to be open to the possibility that we may be wrong.
So the big question remains- what is the ideal diet for humans?
Is it possible we can survive and prosper off pretty much any digestible food source? Heather Wiatrowski presented a great argument in one of our Facebook discussions. Humans are capable of reproducing (a great measure of our survival capabilities) when consuming a HUGE range of foods… even if we only have a single food source. Throughout human history, we’ve had entire cultures that survived on very little variety. Furthermore, a more robust diet doesn’t increase fertility. As long as women maintain a minimal amount of body fat, humans can reproduce.
The idea more or less reflects my “moderation diet” discussed in this post. Actually, the “moderation and variety” part could feasibly be dropped.
So what does this mean? I’m proposing there is no ideal diet for humans. There may be ideal diets for individuals based on intolerance to specific foods. After all, there’s more variability within groups than between groups. What is good for the goose is not always going to be what is best for the gander.
The amount of food is more important. Consume more calories than you burn and you’ll gain weight. Consume less and you’ll lose weight. This does seem to get a little complicated when discussing metabolism as it’s not a static construct. Regardless, the same basic calories in/calories out principles apply.
What is the solution? Try a variety of foods. Continue eating the stuff that has a positive impact. Eliminate those that has a negative impact. Most importantly, understand your optimal diet is probably a little different than anyone else’s optimal diet.
Thoughts? Discuss in the comments.