Node Smith, ND

crash diets can cause short term transient deterioration of cardiac function

A very interesting report from the European Society of Cardiology (ESC), recently stated that crash diets can cause short term transient deterioration of cardiac function.1 “Crash diets” are referred to in this report as being synonymous with “very low-calorie” diets or “calorie restricted diets.” These diets have become incredibly popular in recent years, and are often advocated by specialists in medical hygiene and vitalism. This report from the ESC does not warn against these diets.

research on calorie restriction has been extremely favorable

The research on calorie restriction has been extremely favorable for improving metabolic markers and improving disease states. The author of the study, Dr Jennifer Rayner, clinical research fellow, Oxford Centre for Magnetic Resonance, University of Oxford, Oxford, UK states, “These diets have a very low-calorie content of 600 to 800 kcal per day and can be effective for losing weight, reducing blood pressure, and reversing diabetes.” However, the effects on the heart have not been looked at.

Researchers Used MRI to study the effects of a calorie restricted diet on heart function and fat distribution

Using Magnetic resonance imaging (MRI), researchers studied the effects of a calorie restricted diet on heart function and fat distribution in the abdomen, liver and heart muscle. The study included 21 participants. The average age was 52 years and 6 were men. Individuals in the study consumed a diet of only 600-800 kcal per day for 8 weeks. MRI was used at the start of the study, at one week, and 8 weeks to track progression.


At one week, as anyone familiar with calorie restriction and the body’s physiological response to a fasting state would expect, total body fat, visceral fat and liver fat had fallen – 6%, 11%, and 42% respectively. Significant improvements in insulin resistance, fasting cholesterol, triglycerides, glucose and blood pressure were also seen. This is all to be expected.

Heart Fat Content Rose by 44 Percent

However, at week-one heart fat content had actually risen by 44 percent. This could be explained by the heart’s dependence on fatty acids as a fuel source during the diet, but there was also a deterioration in heart function, including the heart’s ability to circulate blood.

8 weeks

At 8 weeks, the fat content of the heart and function had both improved better than what they had been before the diet, and all other measurements continued to improve. The hypothesis on why this brief, transient disruption in cardiac function may occur has to do with the heart being flooded by fat as it is released from the liver to be utilized as an energy source, and simply needing time to adjust.

A Word of Caution for Individuals with, or those who may have, Compromised Cardiac Function

The report acknowledged the expected improvements and advocated calorie restriction as a methodology and treatment for these metabolic conditions. Though it does issue a word of caution for individuals who may have compromised cardiac function from pursuing calorie restriction without first consulting a doctor.


  1. European Society of Cardiology (ESC). “Crash diets can cause transient deterioration in heart function.” ScienceDaily. ScienceDaily, 2 February 2018. <>.
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Node Smith, ND, is a naturopathic physician in Portland, OR and associate editor for NDNR. He has been instrumental in maintaining a firm connection to the philosophy and heritage of naturopathic medicine among the next generation of docs. He helped found the first multi-generational experiential retreat, which brings elders, alumni, and students together for a weekend camp-out where naturopathic medicine and medical philosophy are experienced in nature. Four years ago he helped found the non-profit, Association for Naturopathic ReVitalization (ANR), for which he serves as the board chairman. ANR has a mission to inspire health practitioners to embody the naturopathic principles through experiential education. Node also has a firm belief that the next era of naturopathic medicine will see a resurgence of in-patient facilities which use fasting, earthing, hydrotherapy and homeopathy to bring people back from chronic diseases of modern living; he is involved in numerous conversations and projects to bring about this vision.

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