Metabolism, Digestion, and DNA: What Shapes the Response to Food

Why does the same dietary approach help one person but have almost no effect on another? This is linked to the individual metabolic response to food, which is shaped by many factors — including genetic ones.

Genetic characteristics can influence how the body metabolises carbohydrates and fats, regulates blood glucose, responds to insulin, and tolerates particular foods. This is why identical nutritional recommendations do not always produce identical results.

For the same reason, genetic information is increasingly used as one component of a personalised approach to nutrition.

Why "Healthy Eating" Works Differently for Different People

Most functional conditions and chronic diseases belong to the category of complex (polygenic) traits (Slunecka et al., Hum. Genom., 2021). Individual differences in the response to food do not arise from a single gene or a single mechanism. They are the result of many biological systems interacting simultaneously. Inherited characteristics not only partially determine how you will look and feel — they can also shift the individual metabolic response. Some people find it easier to maintain stable blood glucose after a carbohydrate load; others process fats more efficiently. The reason lies in the specific features of each person's genetic profile.

The response to food cannot be reduced to a single cause. It is the outcome of several systems operating at once: how the body breaks down and absorbs nutrients, how insulin levels respond to them, the state of the digestive tract, and how actively the immune system reacts to what enters the body. To understand this, it helps to view these processes as a single integrated system.

On individual responses to the same diet — Why the Same Diet Produces Different Results in Different People: The Role of Genetics and Metabolism.

What Lies Behind the Response to Food: Several Systems at Once

How the Body Absorbs Carbohydrates, Fats, and Insulin

The most visible influence on the food response comes from how the body processes the main nutrients. A 2024 review describes that variants in genes involved in carbohydrate and fat metabolism shift the individual response to an identical diet: with the same dietary intake, post-meal glucose and insulin levels differ between people (Mansour et al., Nutrients, 2024). One example is the gene FTO (Fat Mass and Obesity-Associated Gene), whose variants are linked to a predisposition to fat accumulation and to individual differences in appetite regulation (Mansour et al., Nutrients, 2024).

Carbohydrate sensitivity and fat sensitivity are distinct axes that do not always align. Some people maintain good blood glucose control but process saturated fats less efficiently; for others it is the reverse. This is why the universal advice to "simply eat less" works unevenly: it does not account for which specific nutrient is problematic for a given individual's metabolism.

A separate axis is insulin sensitivity. The gene TCF7L2 (transcription factor 7 like 2) is among the most studied risk factors for type 2 diabetes: according to a 2021 review, its variants affect pancreatic beta-cell function and insulin secretion (del Bosque-Plata et al., Diabetes, 2021). This influences how the body distributes glucose after a meal: the less efficiently this mechanism works, the more slowly glucose leaves the bloodstream, making a carbohydrate load harder to tolerate. In practice, this means that a diet with a higher proportion of protein and fibre suits some people better than the classic "less fat" approach (Mansour et al., Nutrients, 2024).

On the genetic characteristics of carbohydrate and fat metabolism — Carbohydrate and Fat Sensitivity: How Genetics Shapes the Individual Response to Food.

The Food Response Begins in the Digestive Tract

The digestive tract itself is no less important. A predisposition to inflammatory and functional conditions of the gastrointestinal tract affects how comfortably the body tolerates certain foods. The cause is often attributed to a specific food, when the real reason may lie in how the gut lining and microbiota respond to dietary components. A 2024 review shows that the composition of the gut microbiome partly depends on inherited characteristics and itself shapes the response to identical foods, including gluten and fermentable carbohydrates (Mansour et al., Nutrients, 2024).

The mechanism unfolds gradually: inherited characteristics alter the sensitivity of the gut lining and the composition of the microbiome; the response to certain dietary components shifts; and this manifests as bloating, discomfort, or erratic digestion after particular foods.

Immune Response and Inflammation

The immune system operates along its own axis. Food intolerance and chronic low-grade inflammation alter how the body reacts to a diet. Here it is especially important not to conflate predisposition with diagnosis: inherited characteristics of the immune response raise or lower the likelihood of certain reactions, but do not predetermine them (Mansour et al., Nutrients, 2024).

The Rate of Metabolism of Individual Substances

How quickly the body processes and eliminates various compounds also matters. A clear example is the gene CYP1A2 (cytochrome P450 family 1 subfamily A member 2), whose variants are linked to the rate of caffeine metabolism — which is why some people can drink coffee in the evening without issue while others find it keeps them awake until the early hours (Mansour et al., Nutrients, 2024).

What a Genetic Test Shows — and What It Does Not

A genetic test does not measure the current state of the body the way a blood test does. It reveals the inherited context: what the body is predisposed to and how this may influence the response to food. The Apixmed Prism DNA test Digestion, Immunity & Metabolism assesses several interconnected systems:

• dietary factors: carbohydrate and fat absorption, insulin sensitivity, sugar cravings, and individual characteristics of substance metabolism;

• digestive tract status: predisposition to inflammatory and functional gastrointestinal conditions;

• immune response: characteristics of the immune response and predisposition to autoimmune conditions;

• resistance to infections.

Together, these data make it possible to assess not individual genetic variants but how the combination of biological systems may influence the metabolic response to food. A genetic report does not contain ready-made recommendations or diagnoses. Its purpose is to show which systems may warrant closer attention and further evaluation (Wuni & Vimaleswaran, Lifestyle Genom., 2024).

On the genetic factors associated with glucose regulation and insulin action — Insulin Sensitivity and the Risk of Type 2 Diabetes: The Genetic Dimension.

What to Do with This in Practice

The test results should not be treated as a ready-made action plan. They help identify which characteristics of the body are worth considering when building a nutritional plan, undergoing assessment, or choosing a next step. This makes it possible to:

• structure the diet with personal carbohydrate and fat sensitivity in mind, rather than following generic schemes;

• take into account a predisposition to gastrointestinal dysfunction if certain foods regularly cause discomfort;

• discuss genetic test results with a doctor, combining them with symptoms and findings from other assessments.

None of these steps overrides the fundamentals: diet quality, sleep, and physical activity. But it makes them more effective, because knowing your own genetic characteristics means orienting yourself by your own biology rather than averaged advice (Antwi, Curr. Nutr. Rep., 2023).

The Food Response as the Outcome of Interacting Systems

The response to food is not always a measure of discipline. It is the outcome of nutrient metabolism, insulin sensitivity, digestive tract status, and immune response working in combination. Inherited characteristics shift these processes, which is why the same diet predictably produces different results in different people. Genetic context does not make nutritional choices on your behalf, but it shows what your body is working with and how. This information helps interpret the body's responses to food more precisely and supports informed decision-making together with your doctor.

Genetic test results are not a diagnosis and do not replace a consultation with a doctor. The Apixmed Prism report provides genetic context that complements clinical test results and supports informed decision-making together with your physician.

Sources

1. Mansour, S., Alkhaaldi, S. M. I., Sammanasunathan, A. F., Ibrahim, S., Farhat, J., & Al-Omari, B. (2024). Precision Nutrition Unveiled: Gene–Nutrient Interactions, Microbiota Dynamics, and Lifestyle Factors in Obesity Management. Nutrients, 16(5), 581.https://doi.org/10.3390/nu16050581

2. del Bosque-Plata, L., Martínez-Martínez, E., Espinoza-Camacho, M. Á., & Gragnoli, C. (2021). The Role of TCF7L2 in Type 2 Diabetes. Diabetes, 70(6), 1220–1228.https://doi.org/10.2337/db20-0573

3. Antwi, J. (2023). Precision Nutrition to Improve Risk Factors of Obesity and Type 2 Diabetes. Current Nutrition Reports, 12, 679–694.https://doi.org/10.1007/s13668-023-00491-y

4. Wuni, R., & Vimaleswaran, K. S. (2024). Barriers in Translating Existing Nutrigenetics Insights to Precision Nutrition. Lifestyle Genomics, 17(1), 122.https://doi.org/10.1159/000541909

5. Slunecka, J. L., van der Zee, M. D., Beck, J. J., et al. (2021). Implementation and implications for polygenic risk scores in healthcare. Human Genomics, 15(1), 46.https://doi.org/10.1186/s40246-021-00339-y