AICAR

The verdict

Our read at a glance.

Whether activating AMPK pharmacologically reproduces the endurance adaptations of training in humans, as it appeared to in untrained mice.

The signal

In the 2008 Cell study, four weeks of AICAR alone increased running endurance by 44 percent in sedentary mice, which is the single result the entire popular case rests on. Rodent work also reports metabolic improvements in high-fat-diet models. AICAR has been examined in human medicine in other contexts entirely, which is not the same as evidence for endurance or body composition.

The unknown

Whether any of the endurance effect appears in trained or untrained humans, at what dose, and by what route. Bioavailability is a real obstacle: the doses used in rodent work do not translate simply, and no human endurance trial has established an effective exposure.

Our read

One striking mouse number, repeated for nearly two decades, with the human study that would confirm or kill it never run. The pathway is real and exercise genuinely uses it. That is a mechanism, not a result.