Why Your Genes Might Explain Why Keto Works (or Doesn’t) for You
I’ve been listening to the Limitless Project podcast recently with an avid interest.
It’s French — presented by a Frenchman named David Nicolas who became convinced that the carnivore and low-carb approach was transforming his health, and has since devoted hundreds of episodes to interviewing the researchers, practitioners, and clinicians who are doing the most interesting work at the edge of nutritional science.
Most of the nutritional content I consume is in English. The Limitless Project is where I follow this space in French (as after all, I am French and now live in France!) — and episode 77 with Marion Kaplan is one I’ve come back to multiple times.
Because it answered something I’d been wondering since I started: the connection between keto and genetics — and why keto seems to work brilliantly for some people and barely move the needle for others.
Who Is Marion Kaplan?
Marion Kaplan is a French naturopath and nutritional biologist who has spent decades working with patients on nutrition and health. She’s the author of several books and is particularly known in France for her work on the connection between diet, genomics, and chronic illness.
She is also — and this is what makes her different from many practitioners — someone who uses genetic profiling as part of her clinical approach. She doesn’t just tell patients what to eat based on general principles. She looks at their individual genetic markers to understand how their bodies are likely to respond to different foods and nutrients.
Keto and Genetics: The Basic Idea
The keto and genetics connection starts here.
We all have genes. Many of those genes influence how we process different foods, how efficiently we absorb certain nutrients, how our bodies respond to dietary fat, how we metabolise glucose. These aren’t fixed destiny — they’re tendencies. But they’re meaningful tendencies.
For example: some people carry a variant that makes them slow metabolisers of certain fats. For those people, a high-fat diet may not produce the same results as it does for someone with a different variant. Some people need dramatically more B12 from food sources. Some people’s bodies don’t convert plant-based omega-3 (from flaxseed) into the active form (DHA) efficiently — which means they need animal sources.
The implication is important: there’s no perfect diet that works identically for every human body. We are not genetically identical. What works brilliantly for one person may be less effective — or in rare cases, actively problematic — for another.
This doesn’t mean nutrition research is useless. The principles Kaplan talks about — reducing refined carbohydrates, prioritising animal protein and fat, eliminating processed foods — hold across most genetic profiles. But the fine-tuning of how much fat, which specific foods, which supplements, how strict the carbohydrate restriction needs to be — that can vary significantly between individuals.
What This Means for Keto
Kaplan’s keto and genetics research shows that keto is, for most people with metabolic and inflammatory issues, a profoundly useful intervention. The reduction in blood sugar and insulin, the production of ketones, the anti-inflammatory effects of removing refined carbohydrates — these benefits apply broadly.
Here are the three ways keto and genetics interact that changed how I think about my own results:
Some people feel terrible on keto in the early phases not because keto is wrong for them, but because they haven’t addressed their micronutrient status first. If you’re going into keto with low magnesium, low B vitamins, or poor thyroid function, the adaptation phase can be brutal — not because your body is rejecting the diet, but because the diet is placing demands on systems that are already depleted.
This hit home. I had a rough first month on keto. Now I take magnesium every evening, B complex in the morning, and I’ve noticed the difference.
Genetic variants can affect how strict you need to be. Most people can handle occasional higher-carb meals without fully knocking themselves out of ketosis. Others — particularly those with certain insulin sensitivity variants — need to be more careful. Knowing your profile helps you calibrate.
Animal foods matter, and why they matter is genetic. Kaplan is clear: the most bioavailable forms of nutrients critical for brain and metabolic health — B12, iron, zinc, complete proteins, DHA — come from animals. For most people, plant-based substitutions are inferior. For some, they’re close to useless depending on their genetic variants.
The Practical Takeaways
This episode reinforced several things I was already doing, and gave me new context for why:
- Magnesium matters, especially on keto — Keto increases magnesium excretion. Deficiency is extremely common and can cause exactly the symptoms people blame on keto itself: fatigue, muscle cramps, sleep problems, anxiety.
- B vitamins from food first, supplements if needed — Meat and eggs are the richest dietary sources of the B vitamins most critical for mental health and energy.
- Protein is not optional — Kaplan, like Dr. Stacy Sims and Dr. Georgia Ede, emphasises that most people (especially women) significantly under-eat protein. And the consequences — poor muscle mass, poor mood, poor brain function — compound over time.
- Be patient with adaptation — The keto adaptation period (weeks one to four) is often genuinely uncomfortable. This is normal. It doesn’t mean you’re doing it wrong.
Why I Find This Approach Compelling
I’m not a scientist. I’m not a nutritionist. I’m a woman who has been paying attention to how food affects how I feel for the past year, and who has read widely enough to start seeing patterns.
What I find compelling about Kaplan’s keto and genetics approach is not the complexity — it’s the permission it gives to stop comparing yourself to someone else’s results.
Your best friend went keto and lost weight effortlessly. You’re doing the same thing and it’s slower. That might be about genetics. Or hormones. Or micronutrient status. Or the specifics of how strictly you’re implementing it. It’s probably not about willpower.
Eat real food. Prioritise protein. First reduce and then eradicate sugar and refined carbohydrates. Eliminate seed oils. Supplement thoughtfully. Pay attention to how you specifically respond.
That’s the principle. The fine-tuning is personal.
What to Take From This
Here’s what the keto and genetics research actually means in practice:
- Supplement magnesium on keto — This is the most commonly overlooked and most commonly needed supplement. 300–400mg magnesium glycinate or bisglycinate in the evening is a good starting point.
- Eat your B vitamins from animals — Meat, eggs, liver if you can stomach it. These are more bioavailable than any supplement.
- Prioritise protein at every meal — Aim for your weight in kilograms × 2g as a minimum daily target on keto. More if you’re strength training.
- Give adaptation time — Four weeks minimum before drawing conclusions about whether keto is working for you.
- Get curious about your genetics — Tests like 23andMe or similar services give you the raw data. Practitioners like Kaplan use this for fine-tuning. It’s not essential but it’s fascinating.
Why This Belongs in “Body”
My blog is organised around my Tree of Life: Roots, Body, Mind, Heart, Soul, Purpose. Each section represents a part of my life that needs attention.
This belongs in Body because it’s about understanding the physical machinery of how we respond to food — specifically the beautiful, annoying, fascinating reality that each of us is a unique biological system. Body is where I track everything to do with health, nutrition, and the ongoing experiment of keeping this particular body functioning well.
The keto and genetics piece is new to me. I’m still learning it. But even understanding the principle — that my body has its own particular tendencies and requirements — has changed how I approach my own health. Less comparing, more observing. Less following the exact protocol someone else swears by, more paying attention to what my body says.
Notes from Soph | Learning, not perfection.
Are you keto, or curious about it? I’d love to hear what you’ve noticed about how your body responds — leave a comment or reach out.
Source Details:
Limitless Project Podcast — Episode #77: “Keto & Genomics”
Guest: Marion Kaplan, naturopath and nutritional biologist
Host: David Nicolas
🎙 Marion Kaplan: https://limitless-project.com/marion-kaplan/
Available at limitlessproject.fr (French)
