How to Read This Guide Each supplement is rated A (strong consistent evidence), B (moderate evidence), C (weak or conflicting evidence), or D (no meaningful evidence or evidence of harm). These ratings reflect the totality of human clinical trial data, not mechanistic plausibility or manufacturer claims. A supplement can have a biologically plausible mechanism and still have no evidence of meaningful effect in humans — many do. The supplement industry generates over $140 billion annually, yet fewer than a dozen supplements have Grade A evidence for fat loss. This creates a massive gap betwe…