ok, we all hear how supplements have different effects on different people and how some supplement companies claim that research proves their product works.
Here is an example of a study, just published in Nature Chemical Biology (a very reputable and high profile journal for all you non-scientists). It is about the effects of small molecules Aicar and GW1516. I have never heard of or seen the products myself, but to be honest, I don't look.
Without further ado, I present the results of the published work.
Skeletal muscle is a highly adaptable tissue that responds to repeated exercise by altering its contractile properties and its metabolism. For example, endurance training results in an increased capacity to generate energy (in the form of ATP) from aerobic pathways. An intriguing possibility is that small molecules that activate the pathways triggering these adaptations might mimic the effects of training without the accompanying sweat and effort. A step toward achieving this goal is reported in a recent paper by Narkar et al.1.
Wang et al.2 had previously shown that muscles of transgenic mice expressing an activated form of PPAR- contain a greater proportion of type 1 fibers (characterized by a more efficient form of myosin and a higher oxidative capacity) and display increased endurance. PPAR- is a transcription factor of the nuclear receptor family; its natural activating ligand remains unknown, although one idea is that it is a fatty acid metabolite generated during muscle metabolism. However, small molecules that activate this receptor (for example, GW1516) have been developed. Narkar et al.1 now report that although prolonged treatment of mice with GW1516 induced a subset of genes involved in fatty acid oxidation, it did not increase endurance on its own. However, when the drug was combined with treadmill training, gene expression, mitochondrial mass and endurance all improved more than with training alone (Fig. 1).
See below for Fig. 1
Now, all this sounds great right? Basically these drugs switch on genes that increase the oxidative breakdown of fats, which give you literally unlimited energy for endurance exercises. This is exactly what these drug companies claim as "scientifically proven" or in many cases, even less data than this.
Now, read the part below. This is why a lot of supplements don't seem to work for many people.
Before aspiring athletes start taking GW1516 or AICAR as training substitutes or additives, it should be pointed out that in human athletes undergoing high-level endurance training (as opposed to sedentary mice maintained in a cage), both of these pathways will already be regularly activated and the drugs may yield no additional benefit. It is also worth pointing out that the increases in endurance seen in these studies were in exercise of moderate intensity, where there is a greater reliance on fat as a fuel. These conditions may magnify any effects of GW1516, whereas in a human athletic event of an hour or less (when carbohydrates would be the primary fuel), any performance benefits of GW1516 would be minimized. The real benefit of drugs that activate PPAR- and AMPK may lie in treating people who would receive health benefits from regular exercise, but who are unable to tolerate it. Indeed, the current front-line treatment for type 2 diabetes (a condition associated with obesity and a sedentary lifestyle) is the drug metformin, whose therapeutic target now seems to be AMPK in the liver9.