The Truth About Peptides, NAD, Fasting, & Other Health Trends

There are big levers and little levers when it comes to your health. The big levers aren't sexy: move your body, eat mostly whole foods, sleep, manage stress, and stay connected to real people in real life. Those are the things that, according to the data, blow everything else out of the water. The little levers, the protocols, supplement stacks, peptides of the month, can only move the needle on the margins.

That's the framework researcher Rachele Pojednic laid out for me on this week's episode of the mindbodygreen podcast, and it's the clearest way I've heard anyone explain why so much of the wellness world just feels like noise. As Pojednic put it, if you don't have the foundation down, "there ain't nothing a peptide's gonna do for you."

I'm of the belief that peptides can be genuinely useful for the right person in the right situation, but Pojednic gave me a reality check, and I know I'm not the only one who needs it.

She reminds us that we have very little human data on peptides. We don't know safe doses or how long you should cycle on or off. She even shared compelling evidence against peptide stacking, citing worm studies where stacking supplements was actively antagonistic.

There's also a sourcing problem. A lot of what's circulating right now are "research use only" peptides, which sounds official, but is really just legal cover for gray-market products manufactured offshore. If you're injecting something that says "not for human consumption" on the vial, that company has zero liability if something goes wrong.

That being said, there are a few specific peptides Pojednic is excited about. BPC-157, known for injury recovery and gut healing, has some human data, even if the studies are small. She said MOTS-c is interesting for muscle recovery, regeneration, and visceral fat. Pojednic also mentioned Pep-19, an oral peptide already available in the U.S., which has been studied in both mice and humans and shows promise for metabolism, visceral fat, and even sleep quality through its effects on mitochondria.

What she's most cautious about are growth hormone secretagogues: if you stimulate growth across the board, everything grows, including things you don't want growing (like cancerous tumors).

Pojednic wants to make it very clear that NAD is not a peptide. NAD is short for nicotinamide adenine dinucleotide, a molecule that plays a central role in how your cells make energy and repair DNA. NAD levels decline with age, sun exposure, and alcohol. And yes, you want to support them.

The problem with NAD IVs is that NAD can't get directly into your cells. There's no transporter for it. So when you inject straight NAD into your bloodstream, your kidneys and liver treat it like something that doesn't belong there, and you essentially pee it out. In other words, the NAD IV parties you see influencers doing on Instagram are probably not doing what people think they're doing.

If you're concerned about declining NAD levels, Pojednic recommends taking NR (nicotinamide riboside) or NMN (nicotinamide mononucleotide). These molecules occur naturally in food, so your body knows how to use them. They can get into cells and help your body make NAD from the inside. Both have solid and roughly equivalent science behind them right now.

Pojednic is a huge fan of creatine (and so am I). It's one of the most researched supplements in existence, and the dose has long been established at around five grams. There's also emerging data suggesting that higher doses (think 10 to 20 grams) may have benefits for brain health and sleep, though that research is still early.

The reason Pojednic cares so much about creatine comes down to muscle. "Muscle is the tissue of longevity," she says. When muscle declines with age, metabolism slows, visceral fat increases, and brain health starts to suffer. Creatine supports muscle, and that matters across your entire lifespan.

But here's the caveat she's emphatic about: creatine alone won't build muscle. When her research group looked at supplements for women and muscle health with aging, creatine, omega-3s, and vitamin D all showed up as beneficial, but all of them were dwarfed by the effects of exercise. You can take all the creatine you want, but it's not going to do much if you're not strength training.

Same goes for protein and amino acids. If you're spending money on an amino acid supplement that doesn't contain at least 2.5 grams of leucine, the amino acid that triggers muscle protein synthesis, Pojednic says you're wasting your money. Check the amino acid profile on your protein powders. She considers no leucine on the label is a major red flag.

There is real data on time-restricted eating. But the way most people are doing it, especially women, is basically the opposite of what the research supports.

Most people fast by skipping breakfast and eating late into the evening. This may lead to weight loss in the beginning because of the decrease in calories, but then the fatigue sets in, sleep gets worse, and the whole thing falls apart.

The data actually shows the benefits of fasting come from stopping food intake two to four hours before bed, not from skipping breakfast. Eating earlier in the day, letting your body have a long overnight rest-and-digest window, then fueling up in the morning—that's the pattern that improves sleep, supports circadian rhythm, and helps with visceral fat and metabolic markers like blood pressure and triglycerides.

The version most people are doing is cutting calories in the short term, but it's also disrupting sleep and leaving people exhausted. As Pojednic put it, we're "this close to being right," but getting it so wrong that we're making people feel worse.

Pojednic is a scientist so she loves data, but she also recently took off all her wearables because she knew she was stressed and didn't need the negative reinforcement. Data is great, but that balance is key.

Pojednic often finds people getting worked up over a single biomarker, or bad sleep score, but a single data point is just a snapshot. What matters is the trend over time.

She used HbA1c (a marker of how well your body is metabolizing sugar) as an example, explaining that reading of 35 may technically be "normal," but it becomes concerning if it's part of a decade-long upward climb that your doctor isn't flagging. The same principle applies to hormones, inflammation markers, and other labs that fluctuate based on recent activity. If you did hard cardio the day before your blood draw, your CRP (an inflammation marker) and creatinine will likely be elevated.

The wellness industry is brilliant at getting your attention, but it's not always great at pointing it in the right direction.