What is the 72 Hour Sardine Fast Metabolic Reset?

And why would you want to do it?

This week, I did the 72 Hour Sardine Fast with my friend Luke.

Why would we do this? January reset, that’s why. With the holidays behind us and a few extra pounds around the middle, we wanted to give the year a kickstart and find out what benefits small, oily fish can bring.

Our experiences were like night and day. One of us loved it. One of us did not.

Keep reading to find out what happened!

What is the 72-Hour Sardine Fast, and Why Would You Do It?

During the 72-Hour Sardine Fast, you eat only sardines for three days. You can eat as many sardines as you want, whenever you want. You can also have water, black coffee, or tea with nothing in it.

The sardines can be eaten from the can or pan-fried/ air-fried for added crispiness.

I heard about this challenge in an interview with Dr. Boz (Annette Bosworth, MD). From Dr. Boz: Kickstart Metabolism In 3 Days With Sardines, and her client who ate Sardines for 100 days?!

Yeah, you read that right. Some crazy lady voluntarily ate only sardines for 100 days. And she didn’t even die.

The Many Benefits of Sardines:

• Flood your body with Omega-3’s! Sardines contain healthy fatty acids, vitamin B12, Vitamin D, calcium, and a pile of other micronutrients.

• Protein in each can - up to 18 G

• Anti-inflammatory

• Boosts ketones and lowers blood glucose

• Increase insulin sensitivity

• Carnivore and keto friendly

• Save on dishes! Eat right out of the can - just like cavemen used to.

---

Ketones

This challenge gets your body to produce ketones and switch to fat-burning. Since sardines are carb-free, your body will naturally do what it has evolved to do: run on fat and convert protein to glucose if necessary.

As the liver produces ketones, blood sugar drops, the body burns fat, and inflammation levels drop. Joint pain relief, weight loss, and lower blood pressure are some reported results.

There’s plenty of evidence that ketones are good for the brain and sharpen your thinking tools.

According to the Carolina Brain Center:

“Research indicates that ketones serve as a more efficient and cleaner fuel for the brain compared to glucose, leading to improved mental clarity, focus, and concentration. Moreover, ketones have shown potential in mitigating the cognitive decline associated with aging and certain neurodegenerative conditions, offering hope for individuals seeking to preserve their cognitive abilities.”

---

Guidelines for the 72 Hr. Challenge:

• Only eat sardines. But the good news is you can eat as many as you want! Packed in oil or water.

• Avoid sardines packed in unhealthy seed oils like soybean oil and sunflower oil! Olive oil is okay.

• Avoid sardines with sauces and flavorings that have added carbohydrates. The goal is low-carb.

• Olive oil, salt, pepper, low-calorie hot sauce, and mustard are acceptable condiments.

• As much water, black coffee, and unsweetened tea as you want.

• No other food of any kind for 72 hours.

  ---

This short-duration challenge is simple because it eliminates all choices. It’s effective because it eliminates all choices. It’s monotonous because it eliminates all choices. But it’s only 3 days! How hard could it be?

---

Tim’s Results

Day 1

• Weight: 182.7 lbs

• Blood Glucose: 5.4 mmol/L

• Ketones: Not measurable

• Overall State: Nothing noticeable

How it went: I ate two cans of sardines, which didn’t bother my stomach at all. I was satisfied, stuffed, and so full that I wasn't even slightly hungry. The thought of food was a real drag.

---

Day 2

• Weight: 179.7 lbs

• Blood Glucose: 4.2 mmol/L

• Ketones: .5 mmol/L

• Overall State: Plenty of energy, mind felt sharp. Happy to be alive.

How it went: My stomach was unsure of itself. It was saying things like, “Am I a little nauseous? Should I induce vomiting? Nah. I’ll just clench the sphincters a little bit. That’ll show this clown not to give me any more sardines.”

Did I listen? No!

I ate a total of 3 cans of oily fish on day 2.

So stuffed. Not at all interested in any more food.

---

Day 3

• Weight: 177.7 lbs

• Blood Glucose: 3.9 mmol/L

• Ketones: 1.5 mmol/L

• Overall State: Mind clear as a bell, emotions very stable, super energetic.

How it Went: An easy day. Loads of energy!

I made myself eat half a can of sardines for lunch. Then I toughed out the entire day, waiting for hour 72.

When the end finally arrived, I ate the last can. So on day three, I consumed 1.5 cans of sardines total. I took the rest of the day off from eating, because I felt like I earned a break!

• Final weight after last can of fish: 176.2 lbs

• Final Blood Glucose: 3.4 mmol/L

• Ketones: 6.5 mmol/L

  ---

Luke’s Experience:

Luke started out great, and reported feeling pretty good for the first two days, except maybe a little low on energy and having to go to bed pretty early.

Day three was a different story.

He reported sardine oil oozing from every pore, and even in his urine. (Unverified since no one else witnessed/ smelled this! 😂) Energy levels were extremely low, and he had a hard time in the last 12 hours. When I asked for a report and mentioned I was feeling great, he texted “You suck.” This led me to believe he wasn’t having a good day.

Luke says no to sardines for the foreseeable future, although he is up for any other crazy fitness challenge I might suggest. That leaves him wide open for shenanigans!

For now, Luke doesn’t plan on repeating the experience, ever. Meanwhile, I’m going for round two next week! I feel better than I have in months.

Valuable lessons from this experiment:

1. Sardines are very filling. If all you eat is sardines, you’ll feel REALLY full.

2. Sardines raise ketones. My levels were the highest I had ever achieved before, even after weeks of a pure keto diet a few months earlier.

3. This challenge can take the weight off fast. I dropped 6 pounds in 3 days. Yeah, I know, it’s “only water weight.” It’s also six pounds of pure inflammation and water with fat in it.

4. I had a sore hip and knee before the experiment, and pain completely vanished by the end of day three. Winning!

   ---

Tips to Make This Fast Work For You

• The day before trying this, it seems to help if you go low-carb, ketogenic, or carnivore to start in fat-burning mode.

• You can add a small spoonful of MCT oil to each meal to boost fat burning and help you go straight into ketosis. This also helps to avoid brain fog if you are primarily a carb burner and going through withdrawals. Be careful with the MCT oil! Too much at once will give you DISASTER PANTS.

• If your stomach is sensitive, pick the skinless sardines. They are a little easier on the system, though you may miss out on some health benefits since many nutrients are in the skin.

• Avoid eating a huge pile of carbs to break your sardine fast. This will shock the system and may cause stomach problems.

---

Would you try the 72 Hour Sardine Fast? Let me know!

---

Subscribe to Time2Thrive — even though I may never write about sardines again! (I know, it’s so terribly disappointing. But I will think of something equally as riveting as sardines, no doubt about that!)