Want to lose weight? Eat MORE!

The ironic evolutionary history of human digestion.

Posted May 12, 2017

Couleur / Pixabay
Source: Couleur / Pixabay

So if you like irony, here’s one for you. A great route to weight loss may actually be to eat MORE! Of course, this statement does come with some strings attached - but there is actually something to it.

In 2010, we were privileged to have renowned Harvard anthropologist Richard Wrangham visit our campus and talk about his work on the evolution of the human diet. His thesis is nothing short of groundbreaking. In a careful examination of a broad range of data, from such fields as archaeology, physiology, and history, Wrangham (see Wrangham, 2009; Carmody & Wrangham, 2009) makes the case that the controlled use of fire by ancestral hominids, going back over a million years, is primarily responsible for what makes us uniquely human. In short, Wrangham makes a strong case that we are the cooking ape.

While there are many kinds of processes that we employ to prepare foods, cooking is essentially the most basic form of food processing. The fact that our ancestors cooked led to dramatic changes in human morphology.

What Does Cooking Do?

We know that cooking (when done right) makes food taste better - but why is that? It takes an evolutionist’s eye to really understand. Cooking makes food more easily and quickly digestible. And it concentrates sugars - which we evolved to find tasty. The fact that cooked foods are more digestible than are raw foods is actually a key to understanding our evolution.

Think about a sweet potato in one of two forms. First, think about picking up a raw sweet potato, skin and all, and just taking a bite. Next, think about eating that same exact potato in mashed form - with some brown sugar and cream thrown in - and, of course, boiled and whipped.

Now think about how long it would take you to eat the raw potato. Even on a dare, I would probably take a good 10 minutes on that one myself.

Next, think about how long it would take you to eat that potato in mashed form. As someone who has been in more than one food-eating competition in my day, I think I am a fair judge of this kind of thing - I could down that in about two minutes tops.

So what does this have to do with evolution? And what does it have to do with weight loss?

Human Diet as Unique Among Primates

According to Wrangham, most humans spend about one hour a day chewing. That is nothing compared with what we see in various other kinds of primates - animals that spend between 4-8 hours a day chewing. Given how easy cooked food (compared with raw food) is to digest, you can quickly see why this is. Chimpanzees don’t have Viking stoves or Cuisinarts …

Interestingly, once cooking came on the scene about 1.5 million years ago (see Wrangham, 2009), the human body started to evolve in an interesting direction: All elements of our digestive system started to shrink. Our intestines shrank - our intestines take up a fraction of our bodies when compared with what we see in other primates. Our mouths shrank. Our mouth is about the same size as the mouth of a spider monkey - and spider monkeys weigh about 4 pounds each! Our teeth shrank too! According to Wrangham, once our bodies had the luxury of needing less expenditure in terms of our digestive system, we are able to “afford” increases in our nervous systems (thus, the brain expansion that is famously connected with human evolution).

In Defense of Raw Foods

So on one hand, Wrangham’s thesis strongly suggests that cooking food is a basic aspect of our evolved condition. This said, as with many things, once we humans figure out some great new technology, we have a tendency to push things to unnatural extremes. Our food processing industry is outrageous - taking our natural tendency to prefer processed foods and doing all kinds of culinary acrobatics to process foods way more than they were ever processed by our ancestors in the African savanna (if you don’t believe me, think about what it takes to bake a cheesecake!).

Our ancestors necessarily had a higher proportion of raw foods in their diets than most of us do now. On top of this, raw food diets have consistently been demonstrated to be effective in terms of weight loss (see Carmody & Wrangham, 2009). And raw foods have consistently shown to help extend the human lifespan and to have all other kinds of health benefits.

So if you really want to adopt a natural (evolution-based) approach to diet - it’s not enough to eat cooked meats. Cooked meats were probably something of a luxury for our ancestors - with the lion’s share of ancestral diets likely being a combination of cooked and uncooked fruits, vegetables, and tubers. This is the kind of diet that our bodies have been naturally selected to experience.

My Experience with Raw Foods

As I’ve written about in a prior post, I’ve undergone a dramatic dietary change in the past year - and it’s worked out pretty well for me.

Without going into too much detail, I’ll say that I eat in a way that maps pretty closely onto the paleo diet (Wolf, 2010) - making sure that I eat a lot of raw fruit and vegetables every day. No, I don’t eat raw sweet potatoes (my mom actually does!) - but I do eat a ton of fruits and veggies.

Here is my diet for a typical day:

  • 2-3 apples
  • 2-3 bananas
  • 1-2 cucumbers
  • ½ a honeydew melon
  • 2-3 tomatoes
  • 1-2 avocados
  • 2-6 eggs (cooked!)
  • Half a chicken or so (baked - with lots of herbs!)

Think about all that food sitting on the counter at once! I actually get a little shade from my wife about having too many fruits and vegetables taking up our kitchen island!

My point in this exercise here is this: I eat a lot of food! I am sure that I eat more food than I used to before I started eating this way - just in terms of the raw amount of food I take in. And I eat all the time! I guess that I am something of a grazer.

But the good news is that most of this stuff is raw - and the caloric content is low. A whole cucumber is about 35 calories, for instance. Think about that!

To some extent, then, a partial-raw-food diet shows how it's not what you don't eat, but, rather, what you DO eat that determines how healthy your diet is. Or, in very shortspeak: Eat your fruits and veggies!

Bottom Line

When Richard Wrangham spoke at New Paltz on the topic of cooking and human evolution, someone naturally asked him about weight loss.

His answer, which I will leave you with, was this: If you want to lose weight, eat raw foods.


Carmody, R. N., & Wrangham, R. W. (2009). The energetic significance of cooking. Journal of Human Evolution, 57, 379–391.

Wolf, R. (2010). The Paleo Solution. Las Vegas, NV. Victory Belt Publishing.

Wrangham, R. (2009). Catching Fire: How Cooking Made Us Human. New York: Basic Books.