MRI assesses effect of crash diets on the heart

Researchers using MRI have shown that very low calorie diets (600 to 800 calories per day) can cause a transient deterioration in heart function, according to research presented at the CMR 2018 meeting in Barcelona, Spain.

The study suggests patients with heart disease should seek medical advice before embarking on this kind of diet, according to a team led by Dr. Jennifer Rayner of the University of Oxford in the U.K.

"Crash diets have become increasingly fashionable in the past few years," Rayner said in a statement released by the European Society of Cardiology (ESC), which organizes the meeting under the auspices of the European Association of Cardiovascular Imaging (EACVI). "These diets ... can be effective for losing weight, reducing blood pressure, and reversing diabetes. But the effects on the heart have not been studied until now."

Rayner and colleagues used MRI to investigate the impact of low calorie diets on heart function and the distribution of fat in the abdomen, liver, and heart muscle, including 21 obese volunteers with an average body mass index (BMI) of 37. Participants followed a very low calorie diet for eight weeks. Each underwent an MRI exam at the beginning of the study period and after one week and eight weeks.

The researchers found after one week study participants' total body fat had fallen by an average of 6%, visceral fat by 11%, and liver fat by 42%. Patients also experienced improvements in insulin resistance, fasting total cholesterol, triglycerides, glucose, and blood pressure.

But also after one week, the study participants' heart fat content had risen by 44%, which was associated with deterioration in the heart's ability to pump blood. However, by eight weeks, heart fat content and function had improved beyond what they had been before the diet began, and all other measurements -- including body fat and cholesterol -- continued to improve, the group found.

"The sudden drop in calories causes fat to be released from different parts of the body into the blood and be taken up by the heart muscle," Rayner said. "After the acute period in which the body is adjusting to dramatic calorie restriction, the fat content and function of the heart improved."

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