Exercise scientist Dr. Mike Israetel is taking a closer look at the supplement industry. In a recent YouTube video aired on July 24, 2025, he broke down his top five most overrated supplements for fat loss and muscle growth.
As a physiologist and amateur bodybuilder, Dr. Israetel practices what he preaches. Running a YouTube platform of over 3.76 million subscribers, he regularly critiques bodybuilders’ workouts and offers advice for accelerating gym gains. This has led him to zero in on popular supplements that might not be living up to their label’s claims.
Exercise Scientist’s 5 Most Overrated Supplements
Find his list of overrated supplements from the YouTube video below:
- BCAA/EAA
- Conjugated Linoleic Acid
- L-Carnitine
- Natural Testosterone Boosters
- Glutamine
BCAA/EAA
According to Dr. Israetel, BCAAs can marginally impact muscle growth, but only in individuals who don’t eat enough protein.
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“Here’s the deal, BCAAs allegedly stimulate muscle growth by directly targeting the mTOR C1 complex, which is one of the essential regulators of muscle growth in the cell,” he shared. “But it turns out that BCAAs, specifically leucine, which is the most powerful of them, really only marginally affect muscle growth if you’re eating not enough protein,” he said.
Conjugated Linoleic Acid
Next, he examined conjugated linoleic acid, and while it shows promising fat loss properties in mice, those outcomes didn’t translate in human trials.
“Conjugated linoleic acid, allegedly, though the police cannot confirm, is a PPAR alpha activator to boost beta oxidation, which is a phase of the fat loss process and is supposed to make you lose fat. But unfortunately, conjugated linoleic acid looks really good when used in rodents; the mice love it.”
“In mice, amazing, in humans, very, very weak outcomes,” he adds.
L-Carnitine
He cautioned that taking L-carnitine orally is often broken down by bacteria in the gut, rather than helping with fat loss.
“The mechanism here is that ostensibly, L-carnitine, in reality, transports long-chain fatty acids into mitochondria, where they would be oxidized, burned up, and you don’t have to have them on your body anymore. But unfortunately, that doesn’t really get into the fat areas; it stays in your gut and gets eaten by gut bacteria.”
Natural Testosterone Boosters
Dr. Israetel shared his thoughts on common natural testosterone boosters, revealing that someone could take them for an entire year and would achieve under one pound of muscle gain.
“We are dealing with substances that claim to raise luteinizing hormones or inhibit aromatase which both would ostensibly increase the amount of testosterone you have in your blood, making you a man.”
“The muscle growth yield for 12 weeks of taking your typical highly dosed testosterone booster is at 0.07 kilograms of muscle, 0.15 pounds of muscle in 12 weeks. If my math isn’t too off, you could take it for a year and still be well under a pound of muscle gain.”
Glutamine
He highlighted glutamine’s limiting factors on recovery and noted that it’s widely available by sticking to a typical diet.
“Remember that supplement that never worked you guys? But people started taking it in the 70s and now people still take it? $267 million dollars in sales, often bundled to many recovery formulas,” he shared.
“It’s supposed to fuel your gut and the immune system which it does. The problem is almost no diet lacks glutamine. Glutamine is almost never the limiting amino acid in any kind of diet or the human body.”
In the past, Dr. Israetel has examined the potential of other supplements, most notably, creatine. Unlike the supplements listed above, Israetel stands by creatine as being one of the most effective and research-backed supplements on the market.
Though some of the supplements he listed could help certain individuals, Dr. Israetel believes the science behind them is lacking. Above all else, he stresses that no supplement regimen will replace a well-balanced nutritional plan.
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