Why Can’t I Lose Weight or Build Muscle Like Others?
By Nicqui Grant, RD(SA), IFNCP
Is Your DNA Holding You Back from Losing Weight or Building Muscle?
Struggling to lose weight or build muscle despite eating right and staying consistent at the gym can be incredibly frustrating. While lifestyle factors like diet, exercise, and sleep are essential, your genetics may be playing a bigger role than you realize. For many people, inherited differences in key genes can influence how their body responds to food, exercise, and even how easily they gain or lose weight.
Take the FTO gene, for instance. Variants in the “fat mass and obesity-associated gene,” (FTO) are linked to increased appetite and greater fat storage. Similarly, MC4R affects hunger regulation, and certain variants can make you feel hungrier or less satisfied after eating, making calorie control more difficult. These factors can make weight loss more challenging, even if you're putting in the effort.
On the muscle-building side, genes like ACTN3 influence your muscle fiber composition. People with the R variant of ACTN3 typically have more fast-twitch muscle fibers, which are better suited for power type exercise and muscle growth. In contrast, those with the X variant may be predisposed to endurance type exercise over strength, potentially making muscle gains slower or less noticeable.
Genes such as PPARG also play a critical role in how your body metabolizes fat and stores energy. Variants in this gene can influence whether your body is more responsive to high-fat or high-carb diets, and how efficiently it burns fat. When combined with differences in the ADRB2 gene, which affects how your body burns fat during exercise, these genetic factors may explain why two people doing the same workouts can see very different results.
If you gain weight easily, even with regular physical activity, your genetics could again be part of the explanation. Besides FTO and MC4R, other important genes like LEPR (which encodes the leptin receptor) influence how your brain perceives hunger and fullness. Some people may not get the same "stop eating" signals, which can lead to overeating despite efforts to stay disciplined. Variants in the ADRB2 genes can reduce how efficiently your body burns fat during exercise.
When it comes to building muscle, genetics also matter beyond fiber type. For example, myostatin is a protein that limits muscle growth, and certain genetic variants can cause your body to produce more of it slowing down your gains no matter how hard you train. Genes like IGF2 (insulin-like growth factor 2) and NRF2 (involved in muscle repair and recovery) also influence how well you respond to strength training and recover after workouts.
This is where DNA testing becomes a useful tool. Genetic tests can identify variants in genes such as FTO, MC4R, PPARG, FABP2, and others that impact how you should eat, train, and recover. For example, if you have certain FTO variants, you might do better with a higher-protein diet as it helps improve satiety and thus control hunger. If you have SNPs in the PPARG gene this may suggest you are poor at metabolizing fat; a lower-fat, higher-carb diet might suit you better.
In addition to all of the above, DNA testing can also reveal how your body responds to caffeine (which affects metabolism), how you manage stress, how efficiently you burn fat during exercise, and how your sleep patterns might influence your weight. While this information isn’t a magic bullet, it offers insight allowing for a more personalized and strategic approach to fitness and nutrition.
In short, if you're not seeing the results you want, your DNA might be part of the reason, but it's also part of the solution. Understanding your unique genetic makeup can help you stop comparing yourself to others and start creating a plan that's designed for you.