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The dietary underdog: An evolutionary answer to the modern lifestyle diseases

How much time have you spent trying different fad diets, figuring out your ideal carb-to-protein ratio, and ‘googling’ the calories you’ve consumed with every snack? We’re guessing a lot. The truth is though, in that quest for the ‘perfect’ diet, we forget that for most of us, eating is largely an emotional decision. We tend to decide on our next meal based on how we’re feeling, which makes it hard to stick to our health goals. What adds to this conundrum is the plethora of posts, articles, and forwards we’re exposed to daily, each claiming how certain foods can boost immunity, improve overall health, or help us shed those extra pounds.

On running a more detailed search, you might then find information that is contrary to something you read just five minutes ago! One health expert advocates X for weight loss, while another pushes Y. Given these inconsistencies, perhaps the best way to understand what’s good for you is to take an evolutionary perspective of the human diet, and use it to fill in the gaps in our current food choices. That being said, the intention of this article is not to recommend any particular kind of diet, but to provide a holistic understanding of the kinds of food that have historically proven beneficial to the human body. So let’s get right to it!


Primordial humans may seem far, far away in time, but from an evolutionary perspective, their existence wasn’t that long ago. In his book Sapiens, Yuval Noah Harari states that the earth is about 4.5 billion years old, and modern humans i.e. Homo sapiens, came into existence 2–300,000 years ago — meaning we are fairly new to planet earth.

Our earliest ancestors were birthed through a split from the ancestors of what we now call chimpanzees and bonobos, around 6 million years ago. Thereafter, they developed the ability to walk upright on two legs, their brain sizes increased, and they learned to use rudimentary stone tools (Klein, 1999). Our earlier food habits resembled that of other primates, but it was around this time that animal meat became an increasingly important dietary component via scavenging and/or hunting. Simultaneously, plant resources that were earlier inedible became digestible when the discovery of fire allowed the development of cooking (Ragir, 2000)

Keep in mind though, that about 50,000 years ago, the living circumstances varied with time and geographical location. This is the reason why some researchers invalidate any relationship between what our ancestors ate to what we eat in present times. They argue that if there was no one universal lifestyle pattern, how can the past provide a model for present dietary recommendations? (Eaton, 2006)

There is, however, a fundamental base to counter this argument and that is, “ the ancestral ways of life during the period from 50,000 to 10,000 years ago were indeed heterogeneous, but their core essentials were similar and differed strikingly from those of the present”.


Many argue that our bodies are not made to consume most of what the modern-day diet incorporates. This includes foods that were introduced thanks to agriculture and animal husbandry, and it undeniably also includes processed and packaged food introduced during industrialization. It is this industrialization-led reliance on processed foods that have led us to where we are today — likely within a 2 km radius of multiple fast-food joints! Some scientists argue that our genes simply haven’t caught up with this dietary divergence and that it could be causing — or at least contributing to — the epidemic levels of chronic disease, such as cancer, diabetes, cardiovascular disease, and obesity that we see today.


A lot of us might think that given the knowledge and access to food items that we have today, our ancestors’ diet may not have been quite as balanced as ours. However, this assumption has been debunked by scientists who argue that due to agriculture, certain foods are more easily available than others, causing dietary disbalances and a rise in lifestyle-related diseases.

So basically, we get less of some very crucial nutrients compared to our ancestors. This begs the question — how was the food that our ancestors consumed different?

One of the striking findings across research studies is that our ancestors most likely consumed over 5 kg of food a day without any sign of obesity, heart disease, or cancer. They regularly consumed no fewer than 55 different kinds of plants, harvesting its nuts, fruits, seeds, underground stems, or eating them as vegetables. It perhaps was essential for them to be open-minded as it allowed them to eat around the year. Of course, earlier humans ate meat as well, but huge amounts of archaeological evidence suggests that plants made up most of their diet. These were eaten raw, boiled or perhaps roasted. And what was the one not-so-secret ingredient in these plants that seems missing from modern diets? It’s fibre!


A definition that has been agreed upon as comprehensive was given by the American Association for Clinical Chemistry. It defines the fibre as the edible portion of a plant that is resistant to digestion and absorption in the small intestine, with complete or partial fermentation in the large intestine. In simpler terms, dietary fibres are a type of carbohydrate — but unlike the other carbohydrates such as sugars, these are not digested in the small intestine and make their way to the large intestine. So when you hear the term ‘whole grains’ and why they are good for you, it’s precisely because the bran, the grain’s fibre-rich outer layer, is intact.

However, to limit our understanding of fibre to bran is an over-simplification. There are several types of fibre found in food and they could formally be classified as:

Dietary Fibre: Fiber that naturally is found in food without any processing Functional Fiber: Fiber that is extracted and isolated from whole foods and added to processed food

While the above classification tells us that one is natural and the other is artificial, it does not tell us anything about its properties or benefits. What is worth mentioning though, is that even nutritionists recommend getting dietary fibre over functional fibre as our bodies are not designed to accept functional fibre as efficiently.

Another way to understand fibre is through a soluble vs insoluble classification. This perspective also helps us reframe the ‘does fibre have calories?’ question to ‘ does your body absorb the calories present in fibres?’ Given that fibres do not get digested or absorbed, it seems natural to assume that they don’t have calories — but it is not that straightforward!


Soluble fibre dissolves in water and gastrointestinal fluids when it enters the stomach and intestines. Most soluble fibre is broken down bacteria in the colon to produce short-chain fatty acids (SCFAs) which, in turn, are used by the body as energy. These calories do not raise blood sugar, so when counting carbs, those in soluble fibre (and insoluble fibre) don’t count towards the total. The soluble fibre is transformed into a gel-like substance which is digested by bacteria in the large intestine, releasing gases and a few calories.

Insoluble fibre does not dissolve in water or gastrointestinal fluids and remains more or less unchanged as it moves through the digestive tract. Since it is not digested at all, insoluble fibre is not a source of calories.

Solubility, then, is a prominent property of fibre — but not the only one. Fibres can be further classified based on two other properties, namely:

Viscosity: Some soluble fibres form a thick gel when they blend with water. This slows down the digestion and absorption of nutrients, resulting in a prolonged feeling of fullness and reduced appetite. These are the fibres that aid in weight loss. Fermentability: The large intestine is home to trillions of live bacteria that play a vital role in weight management, blood sugar control, brain function, and overall health. This intestinal bacteria outnumber the body’s cells 10 to 1. Whereas most foods feed only 10% of your cells, fermentable fibres are mostly responsible for feeding the other 90%. Because humans can’t digest fibre, it ends up reaching the large intestine largely unchanged. Friendly gut bacteria digest (or feeds on) this and uses it as fuel. Most fermentable fibres are soluble, but some insoluble fibres can function in this way

Now that we know how fibres are classified, let’s take a look at the different types of fibres that our body needs to stay healthy: Cellulose & Lignin

These are insoluble fibres that are present in the outer walls of plant cells. When consumed, they pass through the gastrointestinal tract mostly intact and bind with the other food present to help clear the tract.

Inulin & Pectins

These are soluble fibres that make you feel satiated. Inulin forms a gel-like substance and attaches itself to the other food particles to slow down the overall digestion. Both Inulin and Pectins help prevent blood sugar spikes and the cravings that come with it.


These are gel-forming soluble fibres that are prebiotic. This means they are used as food by good gut bacteria. Like soluble fibres, they delay digestion and slow down sugar absorption.

Resistant Starch

Most carbohydrates in your diet are starches. These are long chains of glucose, found in grains, potatoes, and various other foods. But not all of the starch you consume is digested — sometimes, a small part passes through your digestive tract unchanged. This particular type is called resistant starch and functions much like a soluble fibre. There are four different types of resistant starch and the same food might contain more than one. However, it’s important to know that it goes through your stomach and small intestine undigested, eventually reaching your colon where it feeds your friendly gut bacteria, just like fermentable fibres.

Food should ideally travel through your body in 24–36 hours to allow the proper absorption of nutrients. Fibre enables this by slowing the pace at which food travels through the body. While it was earlier believed that fibre simply passed through us, only providing bulk, it is now known that metabolites are actively produced by our fibre-eating gut bacteria. These compounds may have anti-inflammatory, anti-cancer, anti-obesity and blood sugar control effects. Fibre has also been found to bind nutrients, so if you consume fruits in juice form, you are losing out on more than just fibre. Smoothies, on the other hand, allow for greater absorption of nutrients. Depending on what is in it though, disrupting fibre may lead to a higher insulin spike.

We earlier read about how soluble fibres are broken down by gut bacteria to form short-chain fatty acids (SCFAs). Let us go into an in-depth understanding of how this works.

SCFAsare one of the many ways the gut communicates with the brain. They serve as signalling molecules throughout the body — mobilizing hormones and activating nerve pathways and certain cells to regulate appetite, energy balance, body weight, immunity, brain function, and mood states. There are 3 main types of SCFAs — Acetate, Butyrate, and Propionate.

Here’s how it helps both the body and mind: Better Gut Health: Natural detox and promotes weight loss


Fermentable fibres and resistant starch help the good bacteria in our gut to thrive. These not only help maintain balanced pH levels but also help resist pathogens that lead to infections and diseases. Acetate is the highest in ratio and is responsible for this. It also keeps you satisfied longer, preventing your body from absorbing some of the calories in the foods you eat. Medical researchers have thus concluded that those who consume adequate soluble fibres resist weight gain even when put on a high-fat diet. On the other hand, insoluble fibres promote bowel movement and clean up the system.


Given that soluble fibres slow down the release of sugar into the bloodstream and control sugar spikes, it is highly beneficial who suffer from or are at risk of Type 2 Diabetes.


Fibre is not only a great ally in the battle against most lifestyle diseases, but it’s also useful for more immediate life-threatening battles. It’s been shown to reduce the risk of colon cancer by as much as a third and breast cancer by almost 40%. According to a study published in the Annals of Oncology, every 10 gm of fibre you eat is associated with a 10% reduced risk of colorectal cancer and a 5% fall in breast cancer risk.


Pregnancy isn’t always easy on digestion. Increased progesterone levels and an expanding uterus can relax intestinal muscles and slow down your digestive processes. Add to that the stool-hardening effect of iron tablets. Fibre-rich foods are especially beneficial during this period as they ease constipation and help prevent glucose intolerance — a condition that can sometimes lead to gestational diabetes and controls cravings and hunger pangs.


A lack of SCFAs is linked to psychological conditions such as anxiety and depression. Studies show that specific prebiotics known to boost SCFAs curb the neuroendocrine response to stress, dampening secretion of the hormone cortisol. SCFAs also modulate the way the brain processes emotional information, keeping it from dwelling on negatives.

The Indian Dietetic Association recommends consumption of at least 30 gm of dietary fibre daily,r from a variety of plant sources. However, several surveys suggest that the average Indian consumes less than 15 gm of fibre. The easiest way to include the recommended amount of fibre in your meals is by moving towards a plant-based diet focused on fruits, vegetables, whole grains, nuts, and legumes.

A plant-based diet also prioritises healthy whole foods as opposed to processed foods.

Here are some of the different sources of fibre:


Nuts are a great source of fibre and also easy to include in cereals, desserts, fruit bowls, and salads. These also come with the benefit of added proteins, healthy fats, and phytochemicals. Just make sure you avoid anything that you are allergic to!

Whole grains


One of the easiest ways to up fibre intake is to focus on whole grains. A whole-grain essentially refers to the plant’s entire seed, made up of the bran, germ, and endosperm. Refining the grain removes the germ and the bran; thus, fibre, protein, and other key nutrients are lost.

Green leafy vegetables


Deep green leafy vegetables are high on fibre and rich in beta-carotene, vitamins, and minerals. Fun fact, did you know that there are more than 1,000 species of plants with edible leaves? While the Indian diet often includes cilantro as a garnish as well as a variety of sauteed leafy vegetables, it’s a good idea to also consume raw salads to boost your fibre intake.


Fruits are your one-stop-shop for different kinds of fibre, minerals, and vitamins. So include all kinds in your fruit bowls, and don’t forget the nuts and berries.

It’s important to note here that juices — even the raw-pressed, sugar-free kinds — are best avoided. Fruits are high in sugar content, but consuming them whole comes with the benefit of fibre, which helps the body properly absorb this sugar and prevents sudden spikes. If you absolutely must include juices in your diet, try the vegetable kind.


These come packed with both antioxidants and pectin fibre in particular. Plus, since berries have tiny seeds, their fibre content is typically higher than that of many fruits.


Beans are one of the most naturally rich sources of fibre, as well as protein, lysine, vitamins, and minerals. It’s no wonder that many indigenous diets include a bean or two in the mix!

Finally, we’re leaving you with a cheat-sheet that’ll help increase your fibre intake in quick and easy ways.

Add 2 tablespoons of ground flax seeds a day to your food. Sprinkle on salads, grains, or vegetable dishes Eat beans and cereals Bulk up on vegetables Add whole grains like brown rice or quinoa to dishes Include a few servings of low-sugar fruits and berries to your daily diet Include a few handfuls of almonds, walnuts, pecans, or hazelnuts and seeds like pumpkin and chia to your daily diet Start slowly. Switching abruptly to a high-fibre diet can cause gas and bloating Consider a good fibre supplement containing soluble and insoluble fibres if you have trouble getting your fill of fibre (watch for added sweeteners and additives)

Time to get started on your fibre-rich journey to better health!

-Written by Swathy G with inputs from Manasa Rajan


Harari, Y.(2014) Sapiens. 1st ed. New York: HarperCollins Publishers. (2020) Fiber | Health Topics | Nutritionfacts.Org. [online] Available at: <> [Accessed 10 June 2020].

Marano, H. (2020) From Food To Mood. [online] Psychology Today. Available at: <> [Accessed 30 June 2020].

Krouni, Atefeh (2018) Effect of High Fibre, Low Calorie Balanced Diet in Obese Women with Hirsutism: A Randomised Clinical Trail. Journal of Clinical and Diagnostic Research. 2018 Jun, Vol-12(6): IC06-IC09

Klein RG (1999) The Human Career: Human Biological and Cultural Origins. Chicago, IL: University of Chicago.

Ragir S (2000) Diet and food preparation: rethinking early hominid behavior. Evolutionary Anthropology 9, 153–155.

Eaton SB (2006) The ancestral human diet: what was it and should it be a paradigm for contemporary nutrition?: Emory University Atlanta

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