Sardine Fasting

Sardine fasting trend — nutritious food, terrible fasting strategy

A listener asks about the three-day sardine fast trend. The hosts acknowledge sardines are nutritious (omega-3s, bioavailable calcium from bones) but firmly advise against eating nothing but sardines for days. Men's Health called it the latest health trend but warned it's a terrible idea.

"I don't think you should do this. Sardines are really good for you. So including sardines as an oily fish, thumbs up if you enjoy them. But sardine fasting, very different."

No fiber means no gut health — the real problem with sardine fasting

The hosts explain their main concern: sardine fasting eliminates all fiber, starving gut microbes and increasing inflammation. They recommend instead focusing 2-3 days on whole food diversity including sardines alongside greens, lentils, and other nutrient-dense foods.

"We're starving our gut microbes here. And that in turn will increase inflammation within the body because we're not supporting our immune system and we're not supporting our gut lining."

Gut microbes change in 24-48 hours — no extreme fasting needed

Rather than extreme sardine fasting, the hosts recommend a gentler approach. Research shows gut microbial changes are noticeable in just 24-48 hours of improved eating. A couple of days focusing on whole foods achieves more than restrictive mono-diets.

"It just takes 24 to 48 hours to notice microbial changes within your gut. So absolutely, it just takes even just one to two days of focusing on that approach."

Why sardine fasting is not true fasting — mTOR stays elevated

Dr. Cabral explains that sardine fasting is not a real fast because sardines are high in leucine and branched-chain amino acids, which activate mTOR — the exact opposite of what fasting is supposed to achieve. True fasting requires low mTOR and high AMPK for autophagy.

"All right, everybody, we're back with a brand new Cabral concept. Today, we're talking about sardine fasting, and is it actually the biggest breakthrough we've seen in years in nutrition for longevity? Let's break it down here today. Maybe you haven't heard about it, but it is catching on and it's essentially eating nothing but anywhere between two and four cans of sardines per day. That's it. The sardines could be packed in olive oil or maybe just packed in water. You can do the skinless with the bones. There's different interpretations of it. And before we get started, I just want to say is that I've been doing this podcast now for about 10 years, and I've talked about for years the many benefits of sardines. They're one of the absolute best forms of protein that you can get. And it enables you to boost your omega-3 levels, even without supplementation, if you're eating them four plus days per week. So I've seen that in my practice from the very beginning around 2010. I started testing people's omega-3 levels and it was only However, like anything, if something is good, we try to overdo it in our Western-based mindset. And now we're eating nothing but sardines. Here's the thing. Sardines are not a form of true fasting. So it does not go together whatsoever. It does not improve your fat."

Fasting Mimicking Diet vs sardine fasting — opposite approaches

Cabral contrasts sardine fasting with Valter Longo's Fasting Mimicking Diet. The FMD keeps mTOR low with plant foods (veggies + olive oil), while sardine fasting keeps mTOR high due to protein content. He explains that sardine fasting proponents are focused on body transformation, not true cellular cleanup.

"You want that if you want to put on muscle, right? You want to keep mTOR high. I totally get it. One of the people who's a proponent of start eating fasting, it's not like they're not super smart, not like they're not knowledgeable, but they're big on body transformation. They're big on keeping a lot of muscle in their body, which is why they do it, right? But again, it's to keep anabolism high. It's to keep your leucine and branch seed amino acids high. That's the exact opposite of what we want when we're looking for the body to clean house. There can't be fuel for the body to clean house, right? So when you're only consuming, That does keep your body in a catabolic state, a breakdown state where the body's looking for real fuel. Because although there's a lot of micronutrients in your green veggies and your olive oil, there's not a lot of anabolic-based nutrients, protein, right? And we need that to replenish and rebuild the body. Well, a true fast, you're not looking to rebuild the body during that time. And that's why it's a fast. That's why it's That's why it's truly considered a fast. So, there's just a few more things that I want to share with you. It's also not a fast because you are not slowing or shutting down digestion. It's actually very difficult to break down true sardines. So, true dar sardines are higher in purines. I don't want to go too deep down the rabbit hole, but if you're someone with histamine issues, like sardines with the skin on, they're just not going to be the best thing for you. They're a great food, but not every food is right for every individual."

Sardine fasting is really just a hypocaloric day at ~1000 calories

Cabral breaks down the math: 70g protein plus 70g fat from sardines equals roughly 1000 calories per day. He concludes sardine fasting is simply a hypocaloric day with anti-inflammatory benefits from omega-3s and stable blood sugar, but it won't lower mTOR, IGF-1, or increase autophagy.

"Yes, you are then balancing insulin to a greater degree. Sardines are an amazing anti-inflammatory. Again, it's one of our favorite foods to include in people's diets. So it's not like I'm not saying they're not great. I've talked about it for years. I think I've never talked about anything more than sardines and wild blueberries, right? So like an olive oil. Okay. So like those are my three foods that I tell everyone. If you can't eat them, you want to eat them. They're that great for you. But I actually want to keep the science, the science, and I want to keep the marketing out of it. Our sardine fast is not."

The 72-hour sardine challenge — protocol details and what to expect

Dr. Boz outlines her 72-hour sardine challenge in detail. The challenge starts at the first bite and you must eat a can at the 72nd hour. Eat whenever hungry with no limits, but only sardines in oil. Day one is the hardest because bile production hasn't ramped up yet, causing burping and GI distress.

"One of the challenges is this 72 hours of only sardines. The sardine challenge starts with the first bite of sardines. And on the 72nd hour, you need to eat the last can of sardines."

Best ketone numbers come the day after the sardine challenge

Dr. Boz shares clinical data from her 21-day program. By day three of the sardine challenge, glucose-to-ketone ratio is dramatically improved. The peak benefit actually comes the day after — ketones hit 3-4 mmol as a group average, and glucose drops 15-30 points. Ketones beget ketones.

"The best ketone numbers of the whole thing are on the day after the sardine challenge. Their ketones are high, like I'm talking three to fours as a group."

Mastication triggers bile production — why eating sardines beats supplements

Dr. Boz explains the physiological mechanism behind the sardine challenge. Chewing (mastication) triggers cholecystokinin release and signals the parotid glands, which in turn stimulates bile production from the gallbladder and liver. This is why eating whole sardines works better than just taking MCT or omega-3 supplements.

"I had diarrhea. And they'll chirpy, chirpy. And I said, keep going because when your body makes these hormones, it will take a signal from what it has done recently. So the choocystokinin you eat today will be signaled in your parotid glands and when you masticate, when you chew. And that signal is missing when you have either been fasting too much or you've been eating a lot of particleized food without a high fat content. No better way to fix that than to chew on some sarins."

SMASH fish — sardines, mackerel, anchovies, salmon, herring all work

In the Q&A, a listener asks if herring can substitute for sardines. Dr. Boz confirms any SMASH fish works — sardines, mackerel, anchovies, salmon, or herring. The smaller the fish, the lower the mercury and the more absorbable the omega-3s.

"It's an acronym of SMASH. It's sardines, mackerel, anchovies, salmon, herring."

Omega-6 to omega-3 ratio and which cooking oils to use

The episode covers practical guidelines for oil consumption, addressing which cooking oils to use instead of seed oils and where seed oil concerns may be overblown based on the actual science of oxidation and processing.

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Origin story of sardine fasting — Dr. Squat's cancer remission

Dom D'Agostino tells the origin story of sardine fasting. He developed the protocol while working with Fred Hatfield (Dr. Squat), who had metastatic prostate cancer and was given 3 months to live. Hatfield ate one can of sardines per day for a week each month, went into rapid remission, and lived another 8 years.

"I like to do what I call, I mean, I kind of coined it, it's like sardine fasting. And I had a cancer patient a long time, one of the first that I sort of engaged with, his name was Dr. Fred Hatfield. So he was like kind of a famous Dr. Squat."