Fitness | LifestyleCheck: what are common causes?

The question of common causes for fitness or lifestyle issues cannot be answered generically, as it depends heavily on individual context. From a scientific perspective, both genetic factors and lifestyle/environment play a role. Genetic variants such as TCF7L2 (increased diabetes risk) or ACTN3 (muscle fiber type) have small, well-documented effects that are often overshadowed by diet, exercise, sleep, and stress management. Direct-to-consumer DNA tests like MyBody-X can identify these variants, but they do not provide a diagnosis or exact dietary prescription. Evidence for personalizing lifestyle solely based on such tests is weak. Instead, continuous glucose monitoring (CGM) or clinical markers (HbA1c, fasting glucose) are more actionable. Common causes of declining fitness are typically multifactorial: inadequate calorie or macronutrient intake, overtraining, sleep deprivation, stress, or underlying metabolic disorders. A LifestyleCheck should address these areas holistically rather than focusing on single genes. Caveat: Results are not validated for minors and may cause unnecessary anxiety.