Why the Sardine Diet Isn’t a Healthy Way to Lose Weight

• A North Carolina woman says she lost 35 pounds after consuming nothing but sardines and MCT oil for more than three months.
• The sardine-only diet was popularized in 2023 as a 3-day challenge, but some people extended it to weeks or months.
• Experts caution that limiting your diet to a single food for extended periods can have negative health effects.

A North Carolina woman ate nothing but sardines for more than three months — a diet that, she said, improved her health.

In addition to eating four cans of sardines a day, she also consumed MCT oil. This supplement is popular among athletes and bodybuilders and is used as a quick energy source and may support weight loss.

However, Jane Crummett, of Mint Hill, North Carolina, doesn’t consider her eating pattern a “diet.”

“To me, a diet insinuates a beginning and an end. This is my lifestyle and I have no intention of introducing plants back into it,” she recently told Fox News Digital.

Before her months-long sardine-only lifestyle, Crummett was following a “zero carb/carnivore” diet — eating no carbohydrates at all. She also skipped dairy because she “finds it inflammatory,” she told Fox News Digital.

She ended her dalliance of eating only sardines on September 30 after 135 days. While only eating sardines, she lost 35 pounds over three months, she said, and felt better overall.

“My pain has resolved” and her inflammation has decreased, she told Fox News Digital.

Despite her restrictive diet, Crummett said she is healthy and sees a doctor regularly. She plans on reintroducing other meats back into her diet under the guidance of a doctor.

“My ultimate goal is to have sardines for breakfast every day with MCT oil and incorporate normal beef, pork and/or chicken back into my diet,” she told Fox News Digital.

Crummett is not alone in embracing a sardine-only diet.

Last year, Patti Bodner, a 67-year-old Florida grandmother, told Yahoo Life that she lost weight while following a three-day sardine challenge. She also said her blood sugar levels went back to normal, and she was able to stop using the insulin she was taking for type 2 diabetes.

It is not clear if she was able to maintain these changes after the end of the three-day experiment.

This challenge, as the name suggests, involves eating only sardines in oil for 72 hours. You are also allowed a carb-free hot sauce or other seasoning, salt, water and black coffee.

While the sardine-online diet has gained in popularity, there are no scientific studies to back up the claims or to show how safe it is, especially when followed for months instead of days.

“I have significant concerns about anyone consuming a single food — like sardines — exclusively for several days or months,” said Grace Derocha, a registered dietitian and spokesperson for the Academy of Nutrition and Dietetics.

“While sardines are a nutrient-dense food packed with omega-3 fatty acids, protein, calcium and vitamin D, relying on one food alone poses serious nutritional and health risks,” she told Healthline.

Keeping in mind “that food is fuel and the ingredients in that fuel supply every cell in our body with what they need to maintain health, there would be some long-term negative effects of eating a single food,” she told Healthline.

This might include muscle loss, bone loss, nutrient imbalances, and malnutrition, she said, with the negative effects more likely to occur with a long-term restrictive diet.

Shapira added some people might experience short-term side effects, such as:

Derocha pointed out that sardines lack certain “key nutrients such as vitamin C, fiber, magnesium, and certain B vitamins, all of which are critical for immune function, digestion, energy production, and overall health.”

Also, following a sardine-only diet long-term “could lead to deficiencies in antioxidants like vitamins A and E, and phytochemicals — important compounds found in fruits, vegetables, whole grains, and legumes that help protect against chronic diseases,” Derocha said.

Eating a single food for extended periods can also lead to excessive intake of certain nutrients.

Although these may not be harmful in lower amounts — and in some cases are helpful — they can cause problems if you consume too much.

A key one with sardines is sodium, which can increase the risk of high blood pressure and cardiovascular disease, especially if consumed in large quantities over time, said Derocha.

In addition, ”while sardines are excellent sources of vitamin D and calcium, excessive intake could lead to an imbalance in these nutrients, with potential side effects like high calcium levels in the blood, which can affect heart and kidney function,” she said.

“While sardines are lower in mercury compared to larger fish, a diet exclusively made up of fish still raises concerns about cumulative exposure to heavy metals and other environmental contaminants, especially over long periods,” said Derocha.

“For the average person, eating a single food for an extended period of time is not advisable and should be avoided,” she said. “Variety in the diet is crucial to ensure you’re meeting all your nutrient needs and to support overall health and well-being.”

For over three months, a woman in North Carolina ate only four cans of sardines and MCT oil each day. She says this diet helped her lose 35 pounds, resolved her pain, and decreased her inflammation. She plans to reintroduce other meats into her diet but will continue to follow a “low-carb/carnivore” lifestyle.

The sardine-only diet was popularized in 2023 as a three-day challenge by Annette “Dr. Boz” Bosworth, MD, a Florida-based internist who is an advocate of low-carb, high-protein keto diets. Some people have extended this challenge to weeks or months.

Experts caution that limiting your diet to a single food for days or longer can lead to negative health effects. This may include short-term effects such as diarrhea, fatigue, mood swings and constipation, or long-term ones like muscle loss, bone loss, nutrient imbalances or malnutrition.