Diets Debunked

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How Your Diet Controls Your Genes: The Science of Nutritional Genomics and Body Composition

3–5 minutes

Have you ever wondered why some people thrive on a high-fat diet while others gain weight effortlessly? Or why certain individuals build muscle quickly while others struggle despite rigorous training? The answer may lie in nutritional genomics, the fascinating field that explores how the food you eat interacts with your genes, turning them on or off to shape your body and health.

Part 1: How Diet Influences Gene Expression

The Basics of Nutrigenomics

Nutritional genomics (or nutrigenomics) studies how nutrients (macronutrients, vitamins and minerals) and bioactive food compounds (like polyphenols, antioxidants and other compounds) interact with our DNA. Rather than just providing energy, food acts as a biological signal, instructing genes to switch on or off. This happens through several key mechanisms:

Epigenetic Modifications

    • DNA Methylation: Nutrients like folate, vitamin B12, and choline donate methyl groups that can silence certain genes. For example, poor methylation may increase fat storage genes.
    • Histone Modifications: Compounds in broccoli (sulforaphane) and red grapes (resveratrol) alter how tightly DNA is wound around histones, making genes more or less active.

    Transcription Factors

      • Certain nutrients bind to proteins that regulate gene expression. For example:
        • Omega-3 fatty acids activate PPAR-alpha, a gene that enhances fat burning.
        • Polyphenols (found in green tea and berries) activate Nrf2, boosting antioxidant defences.

      Nutrient-Sensing Pathways

        • mTOR: Activated by protein and amino acids (especially leucine), this pathway stimulates muscle growth.
        • AMPK: Triggered by fasting or exercise, this pathway improves energy metabolism and longevity.

        How Different Diets Affect Your Genes

        • High-fat diets may overactivate PPAR-gamma, one of the genes that promotes fat storage (see more below!).
        • High-sugar diets can increase inflammation by turning on NF-kB, a pro-inflammatory gene.
        • Mediterranean diets (rich in olive oil, nuts, and fish) upregulate SIRT1, a longevity gene linked to better metabolism.

        Part 2: How Genes Influence Body Composition (Fat & Muscle)

        Fat Storage: Why Some People Gain Weight Easily

        Your genes play a major role in how your body stores fat. Key players include:

        PPAR-gamma: The Master Fat Regulator

        • Function: Controls fat cell formation (adipogenesis).
        • Diet Interaction:
          • Saturated fats strongly activate PPAR-gamma, increasing fat storage.
          • Omega-3s may partially block this effect, promoting healthier fat distribution.
        • Genetic Variants:
          • People with the Pro12Ala mutation have lower PPAR-gamma activity and may resist obesity better.

        FTO: The Obesity Gene

        • Function: Affects appetite and energy expenditure.
        • Diet Interaction:
          • Those with FTO positive genes are more likely to gain weight on high-carb diets as per studies.
          • High-protein diets may counteract this by increasing satiety hormones like leptin.

        Adiponectin: The Fat-Burning Hormone Influencer

        • Function: Enhances insulin sensitivity and fat burning.
        • Diet Interaction:
          • Monounsaturated fats (olive oil, avocados) have been shown in studies to increase adiponectin.
          • Conversely, processed carbs have been suggested to lower it, worsening metabolic health.

        Muscle Growth: Why Some People Build Muscle Faster

        Genes also determine how efficiently your body builds and maintains muscle. Key factors include:

        mTOR: The Muscle Growth Switch

        • Function: Stimulates protein synthesis when activated by leucine (found in meat, eggs, and dairy).
        • Diet Interaction:
          • High-protein diets appear to maximise mTOR activation for muscle gain.
          • Excessive activation (from constant high protein intake) may accelerate ageing.

        Myostatin: The Muscle Growth Limiter

        • Function: A gene that restricts muscle size (mutations can cause extreme muscle growth).
        • Diet Interaction:
          • Omega-3s and vitamin D may reduce myostatin, enhancing muscle development.

        AMPK: The Energy Sensor

        • Function: Improves fat burning and glucose uptake when activated.
        • Diet Interaction:
          • Fasting and exercise may activate AMPK.
          • Chronic high sugar intake could blunt AMPK, leading to insulin resistance.

        Practical Takeaways

        For Fat Loss

        ✔ Personalise your carbs: You may find a reduced carbohydrate diet more effective at helping you lose weight.
        ✔ Increase omega-3s: They may help to block excessive PPAR-gamma activation.
        ✔ Eat more fibre: Supports gut bacteria that produce short-chain fatty acids, which improve fat metabolism.

        For Muscle Gain

        ✔ Prioritise leucine-rich foods: Whey protein, eggs, and chicken may maximise mTOR activation.
        ✔ Supplement vitamin D: Low levels increase myostatin, hindering muscle growth, and it’s difficult to get enough from the sun in the UK!

        For Longevity & Metabolic Health

        ✔ Follow a Mediterranean diet: Rich in polyphenols and healthy fats, the Mediterranean diet may help to upregulate SIRT1 and AMPK.
        ✔ Avoid processed sugars: Processed sugars may trigger NF-kB, promoting inflammation.

        Final Thoughts

        Your diet doesn’t just affect your waistline—it rewires your genetic expression, shaping everything from fat storage to muscle growth and ageing. By understanding how food interacts with your genes, you can make smarter choices that align with your biology.