According to the researcher at Oxford Centre for Magnetic Resonance, University of Oxford, UK crash diets, also popularly known as meal replacement programs, have been globally followed by millions in the few years. Dr. Jennifer Rayner, clinical research fellow and lead author of the study, explains that these diets typically provide around 600 to 800 kcal of energy and are significantly effective in reducing blood pressure, reversing diabetes, and losing weight. However, there were no prior studies on the effects of these diet plans on the heart.
The study at University of Oxford compared the distribution of fat in liver, abdomen, and heart muscles by using magnetic resonance imaging (MRI) to look into the effects of crash diets on the heart. The study had 21 obese participants with average age of 52 years and body mass index (BMI) of 37 kg/m2. Out of these participants, 6 were men. MRI was conducted thrice during the study firstly at the beginning, secondly at the end of first week, and lastly at the end of the study (after eight weeks). These participants strictly adhered to a very low-calorie diet of around 600 to 800 kcal for eight weeks.
After the first week of the study, liver fat was reduced by an average of 42%, visceral fat by 11% and total body fat 6%. There were also significant improvements in triglycerides, total cholesterol (fasting), insulin resistance and blood pressure of the participants.
But surprisingly, heart function deteriorated including the ability to pump blood and its fat content was elevated by almost 44%. Towards the end of eight weeks, the heart function improved, and its fat content also reduced significantly along with improvement in other factors such as cholesterol level and body fat. With a drastic reduction in calorie intake, fat got released from several body parts into the bloodstream and it was eventually taken up by the heart muscles.
The increased fat within the heart muscles hampered its functioning as it has to choose between fat and sugar as a body fuel. But with time, the heart and the body adjusted to the limited calorie intake, and the heart’s fat content and its function gradually improved.
Dr. Rayner emphasized the need of further studies on this transient reduction in heart function due to limited calorie intake. This study could be of importance for people with heart problems. They need to be extra careful while being on crash diets as it might aggravate the symptoms of their disease such as shortness of breath or even might lead to arrhythmias.
She stressed that people with heart problems must be extra cautious while being on crash diets and should always implement it under medical supervision. Otherwise, crash diets are beneficial for other individuals who aim at losing weight, improving both fat and cholesterol levels as they might not notice any significant changes in heart function.
This study was recently presented at Cardiovascular Magnetic Resonance (CMR) 2018 in Barcelona, Spain.