What Is Bio-Individuality? Why There's No One-Size-Fits-All Diet

When I first went Paleo, I followed the rules. No grains, no legumes, no processed food. And it worked — I felt better, my energy stabilized, the brain fog lifted. But the protocol also said to ditch dairy. So I tried.

Three weeks without cheese, I felt no different. No digestive change, no inflammation, nothing. I added it back and nothing changed there either. My body didn't care. Paleo said dairy was a problem. My body disagreed.

That moment introduced me to one of the most important ideas in nutrition: bio-individuality. It means that what works brilliantly for one person can be completely neutral — or even harmful — for another. Not because one person is doing it wrong, but because we are not the same.

Where the idea comes from

The concept has a specific origin. In 1956, biochemist Roger Williams published Biochemical Individuality, arguing that human beings vary enormously in their nutritional needs, metabolic processes, and even anatomy [1]. Williams documented that people's enzyme activity, hormone levels, and organ structure differed far more than conventional medicine assumed. The idea that there is a single optimal diet for everyone was not supported by the biology.

Williams was ahead of his time. The nutrition establishment spent the next several decades trying to build universal dietary guidelines anyway. The results have been mixed, to put it charitably.

The science has since caught up. A field called nutrigenomics — which studies how your genes influence your response to nutrients — has confirmed that genetic variation shapes everything from how you absorb vitamins to how you metabolize fat [2]. You do not need a PhD to apply this. You just need to pay attention to your own body.

The Inuit example

One of the clearest examples in human history is the traditional Inuit diet. For thousands of years, Arctic populations survived — and thrived — on a diet that was almost entirely animal-based: seal, whale, fish, caribou. Very little plant food, essentially no grains, extremely high fat intake [3].

Conventional nutrition would predict problems. High fat, almost no fiber, limited vegetables. By standard guidelines, this should be a recipe for cardiovascular disease.

It was not. The Inuit had excellent cardiovascular health. Part of the explanation is genetic: research has found that certain Arctic populations carry gene variants that affect how the body processes fatty acids — adaptations shaped by a diet that has been in place for millennia [4]. Their biology evolved to match their food environment.

The takeaway is not that everyone should eat like the Inuit. It is that the Inuit being healthy on their diet is evidence that human beings can thrive on very different food patterns depending on who they are and where they come from. One template does not fit everyone.

What this means in practice

Bio-individuality does not mean "anything goes" or that nutrition is guesswork. The foundations hold for everyone: real food over processed food, adequate protein and fat, avoiding the things that consistently damage gut lining and spike blood sugar. Those are not controversial.

But the details — how much fat, which protein sources, whether you tolerate dairy or nightshades or raw cruciferous vegetables, how many carbohydrates you actually do well on — those are individual. You figure them out by experimenting and paying attention, not by following someone else's template.

My own framework is animal-based first. Beef, eggs, organ meats, fish, dairy — that is the core. Plants are secondary. Some work for me, some do not. That works for me specifically. Someone else might do well with more plant food. What matters is that you are working from real food and actually tracking what your body does.

This is why the Nutritional Therapy Association uses a bio-individual approach. Assessments are not cookie-cutter. The goal is to figure out what this person needs, not fit them into a protocol designed for a statistical average. Average does not exist as a person.

A practical starting point

If you have ever felt like you were doing everything right and still not getting results, bio-individuality is worth taking seriously. The plan might not be wrong in principle — it might just be wrong for you.

Start by removing the most common problem foods across the board: seed oils, refined sugar, processed grains. Those cause issues in nearly everyone. Then pay attention to how you specifically respond to dairy, different protein sources, and carbohydrate amounts. Keep notes. Give changes at least three weeks before drawing conclusions.

You are not a study average. You are a specific person with a specific history, specific genetics, and a specific gut microbiome. The goal of nutrition is not to eat what the guidelines say — it is to eat in a way that makes you feel and function well. Bio-individuality is the framework that makes that possible.

Sources

[1] Williams, R.J. (1956). Biochemical Individuality. Wiley. Overview: https://en.wikipedia.org/wiki/Roger_J._Williams

[2] Ordovas, J.M. & Mooser, V. (2004). Nutrigenomics and nutrigenetics. Current Opinion in Lipidology, 15(2), 101–108. https://pubmed.ncbi.nlm.nih.gov/12671662/

[3] Kuhnlein, H.V. et al. Traditional food systems and Indigenous health in Arctic populations. International Journal of Circumpolar Health. https://pmc.ncbi.nlm.nih.gov/articles/PMC5729304/

[4] Tishkoff, S. et al. (2015). Inuit carry genetic variants affecting fatty acid metabolism. NPR coverage: https://www.npr.org/sections/thesalt/2015/09/17/441169188/the-secret-to-the-inuit-high-fat-diet-may-be-good-genes