October 2026 - Sardine Fast
Metabolic Medical
October 2026 Newsletter
A 72 hour sardine fast is a great way to jump start your mitochondria and metabolic health. This is a protein sparing modified fast (PSMF) that strictly limits carbohydrates to keep insulin low, while providing protein to preserve lean muscle mass. This combination drains glycogen stores in the liver and muscles to lower glucose, stimulates fat burning and the production of ketones that shut down appetite and creates new mitochondria that work better. A 72 hour sardine fast is an effective, metabolic tool made famous by Dr Annette Bosworth (Dr Boz) and Dr Dom D’agostino and used by tens of thousands.
Why Sardines?
Convenient
Affordable
Transportable
Nutritional powerhouse, high in protein, omega 3, collagen, calcium, coenzyme Q10, vitamins B12 and D, selenium and phosphorus.
Portion control
NOT hyper palatable like many modern foods
Very satiating. 1-3 cans per meal will fill most people.
Reduces decision fatigue.
There are a few simple rules to make your experiment successful.
Talk to a health care provider if you are taking blood pressure or diabetic medications. The sudden reduction in carbohydrates is a powerful intervention and may require medication dosage reduction/ elimination.
Do it with a friend. With positive peer pressure you won’t want to let your partner down!
It is easiest if you start reducing carbs to under 20g TOTAL carbs daily for a few days prior to the sardine fast. I also recommend decreasing your eating window to two meals per day.
Drink adequate water and supplement with salt and electrolytes. Black coffee, tea, soda water are great. Nothing sweetened or any creamers- they stimulate insulin and will decrease ketones.
Measure glucose and ketones every morning before, during and after the fast. I like Keto Mojo. Start doing this 2 days prior to the fast.
Weigh yourself at the start of the fast, ideally with a bio impedance scale, to monitor body composition changes.
You can use canned sardines, herring or mackerel.
If these fatty fish make you burp, your bile hasn’t caught up yet. It will. Push through and be patient.
It starts when you open your first can and ends when you finish your last can 72 hours later.
Limit consumption to a maximum of six cans per day. This is approximately 120g of protein and helps to preserve muscle. This lower calorie state will also help create ketones and drop blood glucose.
If the sardines are packed in olive oil, drink the olive oil. Avoid sardines packed in seed oils.
If the sardines are packed in water, consume 1 tablespoon of butter, olive oil, or MCT with each can.
Seasonings are fine if they DO NOT CONTAIN SUGAR/CARBS. Mustard, sugar-free spice mix, hot sauce, pepper, lemon juice are great options. Apple cider vinegar and other acids help to cut the fishy taste.
The sardines can be fried, air fried or eaten straight from the can.
If you are hungry, ask: “Am I sardine hungry?” If you are - eat a can. Try to limit eating to two occasions per day. Ideally shut off eating by 4 PM.
Do not end the fast with a binge--this is key! Plan a meal keeping carbs low, high fat and moderate protein. I love beef flanken ribs because they deliver on all three and they’re delicious!
Weigh yourself at the end. Was there a decrease in your weight or body fat? Did your lean mass change?
Keep checking your glucose and ketones after your fast. You will see your glucose stays low and ketones high for many days after the fast so long as you keep those carbohydrates under 20g/d.
Eating only sardines for three days can seem intimidating. Perhaps you start with one day of sardines and then work up to two or three. View it as a challenge! You were made to do hard things and having a short season of restriction can give you a new perspective on food. Your food is there to nourish and energize us. It is not an emotional support, a comfort tool or a source of pleasure. You may eat for a hunger that is not driven by the body’s need- this is an opportunity to reflect on those other hungers. I hope you enjoy this opportunity to reset your metabolism. More than anything, I hope you see that you are worthy of nutrient dense food, better health and safe food boundaries because you are pretty darn important, beautiful human.
With care,
Jocelyn Foran MD FRCPC DABOM MHP
Comments