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Nutrigenetics guide

Genes are not destiny: how genes and lifestyle work together

Reviewed by Dr. Daniel Wallerstorfer, molecular biologist and founder of Novogenia · Updated: 12 October 2026 · Reading time: 9 min

In short

Most traits related to diet and weight arise from the interplay of many genes with diet, exercise and environment. That is good news: in physically active adults, the effect of the FTO variant was 27% weaker, and people with this variant lose weight in weight-loss programs just as well as others. Studies also show that gene-based advice can change eating habits. For your counseling, this means: genes show where effort pays off most, measured values show the current state – and recommendations are logical conclusions.

Many genes, one orchestra: why no single gene decides

One of the largest genetic studies on body weight analyzed data from up to 339,224 people and found 97 places in the genome associated with BMI. Each of them contributes only a small part: together, they account for about 2.7% of the variation in BMI, and all common gene variants combined for more than 20%, according to the authors’ estimates (Locke et al., Nature 2015).

Picture body weight as an orchestra. Hundreds of instruments play along, each of them fairly quiet. A single gene is a single violin – audible if you listen closely, but it does not decide the music on its own. That holds for many traits you care about in nutrition counseling: hunger, fat distribution, weight trajectory.

Even the “loudest” instrument plays quietly: with FTO, the strongest known genetic signal for obesity, adults with two unfavorable copies weighed about 3 kg more on average (Frayling et al., Science 2007). That is measurable – and it can be influenced, as the next section shows.

Lifestyle turns the dimmer

Genes decide which lamp hangs in the room. How brightly it shines is often regulated by lifestyle – like a dimmer. Three examples from research:

Exercise dims FTO: In physically active adults, the effect of the FTO variant on obesity was 27% weaker than in inactive adults (Kilpeläinen et al., PLoS Medicine 2011).
Saturated fat switches on APOA2: People with the CC genotype had a higher BMI only with a high intake of saturated fat (22 g or more per day); at lower intakes, there was no difference (Corella et al., Archives of Internal Medicine 2009).
Smoking wakes up CYP1A2: A common CYP1A2 variant made a marked difference in caffeine breakdown among smokers – the environment helps determine how strongly the gene comes into play (Sachse et al., British Journal of Clinical Pharmacology 1999).

The message for your clients is encouraging: by changing diet and exercise, they often also change how strongly a gene comes into play. This is exactly where your counseling comes in.

What studies show about genes and lifestyle

How well can genetic information be used in practice? These studies provide answers:

Study	What was studied	Result	What it means for you
FTO meta-analysis, 8 trials, 9,563 participants (Livingstone et al., BMJ 2016)	Do FTO carriers lose weight in weight-loss programs?	Yes, just as well as others – with diet, exercise and drug-based programs.	Unfavorable genes are no reason to give up.
Food4Me, 1,269 participants completed (Celis-Morales et al., International Journal of Epidemiology 2017)	Does personalized nutrition advice work better than general advice?	Yes: less red meat, salt and saturated fat, more folate and a better Healthy Eating Index.	Personal counseling pays off.
Randomized trial, 138 young adults (Nielsen and El-Sohemy, PLoS One 2014)	Does gene-based dietary advice change intake?	Carriers of an ACE variant who received salt advice reduced their sodium intake more than the control group after 12 months.	Concrete, personal recommendations can work.
NOW trial, 140 participants (Horne et al., BMJ Nutrition, Prevention & Health 2020)	Does nutrigenomics help on top of a standard weight-management program?	Only the group with genetic information significantly reduced its fat intake after 12 months (from 36.0% to 30.2% of energy).	Embedded in guidance, genetic information supports follow-through.
Internal Novogenia study, 302 people	Gene-based diet compared with a standard diet	Participants on a gene-based diet lost around 2.4 times more weight than on a standard diet.	An encouraging result from our own research.

Studies without a gene effect also provide valuable insights: in DIETFITS, 609 adults lost similar amounts of weight on a healthy low-fat and a healthy low-carbohydrate diet (5.3 and 6.0 kg), and a pattern of three gene variants did not predict who would do better on which diet (Gardner et al., JAMA 2018). The lesson: with weight, many genes and everyday follow-through work together – which is exactly why counseling that keeps both in view is worthwhile.

Where genes give your counseling a tailwind

With clear links: For gene–nutrient pairs such as LCT and milk sugar or MTHFR and folate, the science is solid; they give you concrete talking points.
As a personal entry point: In Food4Me, personal advice improved diets more than general recommendations – and a genetic analysis makes the conversation even more personal.
As motivation to follow through: In studies, people put gene-based recommendations into practice, for example on salt or fat. With your guidance, this becomes a plan.
As encouragement: An unfavorable FTO result shows that exercise pays off especially well – and that weight loss can succeed just as well.

Genes and measured values: together, the whole picture

In plain language, we often speak of “functioning” and “impaired” genes. This is a deliberate simplification; technically, these are gene variants (polymorphisms) whose effects are described in studies as averages of large groups. With the MTHFR gene, for example, blood folate in women with two impaired copies was 13% lower on average than in women with two functioning ones (Tsang et al., American Journal of Clinical Nutrition 2015).

Vitamin D is similar: people in the least favorable quarter of a genetic score had 2.47-fold increased odds of a blood level below 75 nmol/L compared with the most favorable quarter (Wang et al., Lancet 2010).

For your counseling, this means: genes show you where to look more closely – the measured value shows today’s state. Together, they create a personal picture. If the two don’t match, the measured value sets the direction. Abnormal blood values need a medical work-up.

Clear and credible: finding and recommendation

At Novogenia, we put it this way: the genetic traits determined are well documented, each gene by at least three independent studies. The recommendations derived from them are logical conclusions, not scientifically proven.

This clarity is a strength: your clients know exactly what your recommendation is based on. The same applies to personalized supplements – there, many genes, body data, a questionnaire and blood values flow into one mix, rather than a single gene determining a dose. More in From genetic profile to personalized supplements.

How to talk with clients about genes and lifestyle

Instead of	Better
“Your genes make you fat.”	“Your genes give you a bit of a headwind with your weight. Exercise and diet work for you just as well.”
“This is your diet type according to your DNA.”	“Your genes give hints. Which diet you can stick with long term counts at least as much.”
“Because of MTHFR, you have a folate deficiency.”	“Your genes point to a somewhat slower folate metabolism. Whether you are lacking anything is shown by your diet and blood values.”
“The test is scientifically proven.”	“The genetic traits are well documented. The recommendation based on them is a logical conclusion.”
“There’s nothing you can do about it.”	“Genes are not destiny – let’s see where your effort pays off most.”

Four questions before every gene-based recommendation

Before you turn a genetic report into a recommendation, run through these questions:

Is the trait well supported? Confirmed in several independent studies?
Does it fit the person in front of you? Do the dietary history, body data and blood values match the picture?
Is the recommendation sensible and safe? Less saturated fat or more vegetables fit into any plan; extreme measures based on a genotype alone do not.
Have you labeled it clearly? As a logical conclusion – not as a proven effect.

If all four answers fit, you have a recommendation you can stand behind with a clear conscience and full conviction.

Your role: translating between the lab and everyday life

You translate between the lab and everyday life – and that is where the effect happens. Diagnoses are not part of that: analyses related to disease – such as HLA-DQ2/DQ8, HFE, APOE or thrombosis factors – and pharmacogenetics are medical analyses and, where national law requires it, belong in medical hands. So do persistent complaints. Within this framework, you can achieve a lot: with honest words, concrete steps and the message that genes are not destiny.

How we do it at Novogenia

How we bring genes, measured values and lifestyle together:

Clear language: The genetic traits determined are well documented – each gene by at least three independent studies. Recommendations derived from them are logical conclusions, not scientifically proven.
Blood values first: Our algorithm for personalized supplements uses around 50 genes with three genotypes each, plus body data, a questionnaire and – where available – blood values. Blood values take precedence over genes.
No gene, no dose: A statement like “gene X gives nutrient Y at dose Z” would be incorrect.
Guardrails: Doses range from one third to three times the reference intake, capped at the EFSA tolerable upper intake level.
Said openly: For the finished personalized combination product, there are no large randomized trials proving an outcome benefit over standardized supplementation.

Frequently asked questions

How do genes and lifestyle work together?

Genes set tendencies; lifestyle often regulates how strongly they come into play. In physically active adults, the effect of the FTO variant on obesity was 27% weaker than in inactive adults. With APOA2, a higher BMI appeared only with a high intake of saturated fat. For your counseling, this means: genes show where changes pay off most.

Can unfavorable genes be offset?

Often, yes. A meta-analysis of 9,563 participants from eight randomized trials found that people with the unfavorable FTO variant lose weight just as well as others in diet, exercise or drug-based programs. An unfavorable result is therefore not a verdict but a pointer to where effort pays off.

Does a gene-based diet help with weight loss?

In an internal Novogenia study with 302 people, participants on a gene-based diet lost around 2.4 times more weight than on a standard diet. Independent studies also show that gene-based advice can change fat or salt intake. The recommendations remain logical conclusions – they unfold their effect when they are put into practice in everyday life.

What do I do if the genetic report and a blood value don’t match?

Then the blood value counts, because it shows the current state. Genes describe a tendency; the blood value describes the person today. Novogenia’s algorithm also weights blood values above genes. Abnormal blood values need a medical work-up.

Are gene-based recommendations scientifically proven?

The genetic traits themselves are well documented – at Novogenia, each gene by at least three independent studies. The recommendations derived from them are logical conclusions, not scientifically proven. That is exactly how you should explain it to clients – it builds trust.

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Note: This guide is general information for professionals and does not replace medical or legal advice. The genetic traits determined in a genetic analysis are well documented (each gene included is backed by at least three independent studies); recommendations on nutrition, micronutrients and lifestyle derived from them are logical conclusions, not scientifically proven. Regulations can change; errors and changes excepted.