Tired? Overweight? Anxious? Depressed? Health gurus and celebrity doctors are eager to diagnose—and cure!—whatever ails you. Here’s what the science says about the latest ideas buzzing around the wellness world.

Adrenal Fatigue

Claim: “When your adrenal glands are overtaxed, a condition known as adrenal fatigue or adrenal exhaustion sets in, which in turn can set a cascade of disease processes into motion,” claims Joseph Mercola on his website, mercola.com.

Evidence: “The theory of adrenal fatigue—which was coined by chiropractor James Wilson in the late ’90s—is that overexertion of the adrenal glands as they continuously pump out the stress hormone cortisol eventually leads the adrenals to burn out, resulting in an inability to respond to stress,” explains Rashmi Mullur, an endocrinologist and assistant professor of medicine at UCLA.

Adrenal fatigue affects up to 80 percent of American adults at some point during their lifetime, says Wilson’s book, Adrenal Fatigue: The 21st Century Stress Syndrome. It’s responsible for salty and sweet cravings, being tired for no reason, and more, he claims.

Only one problem, notes Mullur: “No matter how much stress we’re under, our adrenal glands won’t burn out.”

The pituitary (a pea-sized gland in the brain) tells the adrenal glands to produce cortisol. In turn, “cortisol acts as a messenger from the adrenals, and tells the pituitary, ‘We’re good. We’ve made enough hormone. You don’t need to stimulate us any more, ’” Mullur explains. “It’s a self-regulating system.”

The processes that control cortisol production can break down, for example in people who have Addison’s disease (when the adrenals don’t make enough cortisol) or Cushing’s disease (when they make too much).

“But I can test for those diseases, and it’s a very clear ‘Yes, you have this’ or ‘No, you don’t,’” says Mullur.

So why do some people feel so exhausted? Other problems—like thyroid disease, depression, sleep apnea, past trauma, anemia, or stress—could be the culprit.

As for supplements that provide “adrenal support,” don’t bother, says Mullur. When researchers bought a dozen popular ones online, they found thyroid hormone in all 12 and at least one steroid hormone in seven.¹ None of the hormones—it’s illegal for them to be in supplements—were listed on the labels.

Those ingredients could influence hormonal pathways in unpredictable ways, Mullur points out. What’s more, they could interfere with hormone tests, making it harder for your doctor to diagnose problems.

Bottom Line: “The term adrenal fatigue doesn’t capture what people are experiencing, because it’s not an adrenal issue,” says Mullur. “But the burnout and exhaustion are absolutely real. If we doctors dig a little deeper to get to the root cause of those issues, we’re more likely to help patients.”

Leaky Gut Syndrome

Claim: “Leaky gut syndrome is a condition where undigested proteins like gluten, toxins and microbes can pass into the bloodstream,” cautions chiropractor Josh Axe on his website, draxe.com.

“Over time, if leaky gut is not healed, it can lead to food sensitivities, arthritis, inflammatory bowel disease, skin issues like eczema, hypothyroidism, adrenal fatigue, depression, anxiety, ADHD, nutrient malabsorption and autoimmune disease.”

Evidence: “Alternative medicine has embraced the concept of leaky gut syndrome, blaming it for nearly everything that can go wrong with a person,” says Alessio Fasano, director of the Center for Celiac Research and Treatment at Massachusetts General Hospital for Children.

In contrast, “modern medicine disregards leaky gut syndrome as voodoo medicine because of claims that it causes so many problems when there is no evidence,” he notes.

“In my opinion, both camps are wrong.”

The lining of your gut is a single layer of cells that sits between you and the contents of your intestines. Until recently, scientists thought that the cells were so tightly sealed together that nothing passed between them.

Then, “in the ’90s, researchers showed that there are structures—now called tight junctions—between neighboring cells,” explains Fasano.

“They’re like doors, and most of the time we want them closed to keep the bad guys out.”

“There are billions of doors in the small intestine,” Fasano points out. “Depending on the percentage that are open and for how long they’re open, you can have an increase in gut permeability.”

Zonulin, a family of proteins that Fasano discovered in 2000, is the “key that unlocks the door,” he says.

That may explain why researchers report elevated blood levels of zonulin—and increased gut permeability—in many people with celiac disease, type 1 diabetes, Crohn’s disease, and some other autoimmune or inflammatory diseases.²

Unfortunately, “there’s no reliable test for gut permeability,” says Fasano. Most researchers use several tests to measure it.

What’s more, “some people believe that just because you have an intestine that leaks, that’s a problem,” says Fasano. “But that’s not true.”

“It depends on what you find on the other side of the door. If you have a genetic predisposition and a belligerent immune system that doesn’t know how to manage invaders, you may develop disease.”

Fasano’s “holy grail”: figuring out who those people are early in life and preventing gut permeability in an effort to ward off autoimmune disease. But we’re nowhere near being able to do that yet.

Is there any evidence that supplements, probiotics, or Josh Axe’s Eat Dirt diet can heal a leaky gut?

“Of course not,” says Fasano. “How can you claim that these remedies can fix a problem if you don’t even know if someone has it?”

Bottom Line: Don’t waste your time on diets or pills that claim to fix leaky gut.

Boost Metabolism

Claim: “The beauty of your metabolism is that it can be manipulated,” writes self-proclaimed “metabolism whisperer” Haylie Pomroy in her book The Fast Metabolism Diet, which claims to “set your metabolism on fire.”

Evidence: “When we talk about metabolism, we’re talking about the calories you burn when you’re not doing anything, or your resting metabolism,” says Michael Jensen, director of the Obesity Specialty Council at the Mayo Clinic.

“Unfortunately, we don’t have much control over our resting metabolism.”

For example, it slows as you age.

“If you compare a 70-year-old and a 20-year-old with the same amount of fat and lean tissue, the 70-year-old would burn fewer calories at rest than the 20-year-old,” says Jensen.

Women also have a slower metabolism than men, largely because they typically have less muscle. (You have to burn more calories to maintain muscle than fat.)

Even if men didn’t have more muscle, says Jensen, “for any given amount of fat and lean tissue, women burn slightly fewer calories at rest than men.”

Can anything boost your resting metabolism?

“People who gain a lot of extra muscle will burn more calories at rest than before they gained all that muscle,” says Jensen.

But the effect isn’t huge.

“For the average person, muscle accounts for about 25 percent of metabolic rate,” notes Jensen. “So you’d have to gain a lot of muscle before it would have much impact on your resting metabolism.”

Want a bigger calorie burning boost? Spend less time at rest.

“You’ll burn more calories from doing that strength training than you’ll burn from the increased muscle mass,” says Jensen. Or walk, run, bike, or do other aerobic exercise to burn more calories.

And if your resting metabolism is slow, don’t despair.

Jensen’s team tracked people with either high or low metabolic rates. Those in the “high” group burned about 500 calories more per day than those in the “low” group, despite being roughly the same age and having similar amounts of fat and muscle mass. Yet after roughly ten years, weight gain was no different.³

“A low metabolic rate doesn’t mean you’re doomed to gain weight,” says Jensen, “and a high metabolic rate doesn’t protect you from gaining weight.”

Bottom Line: Ignore the hype about resetting or revving your resting metabolism. Instead, get moving.

¹Mayo Clin. Proc. 93: 284, 2018.
²Clin. Rev. Allergy Immunol. 42: 71, 2012.
³Am. J. Clin. Nutr. 104: 959, 2016.