According to lead author Dr Jennifer Rayner, clinical research fellow, Oxford Centre for Magnetic Resonance, University of Oxford, Oxford, UK, ‘crash diets, also called meal replacement programmes, have become increasingly fashionable in the past few years’, these diets have a very low calorie content of 600 to 800 kcal per day (2500kJ – 3360kJ).
After one week, total body fat, visceral fat and liver fat had all significantly fallen by an average of 6%, 11%, and 42%, respectively. This was accompanied by significant improvements in insulin resistance, fasting total cholesterol, triglycerides, glucose and blood pressure.
Alarmingly, in addition to this, after one week, heart fat content had risen by 44%. This was associated with a deterioration in heart function, including 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
Dr Jennifer Rayner explained that, "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," she continued. "The heart muscle was swamped by fat thus worsening its function. After the acute period in which the body is adjusting to dramatic calorie restriction, the fat content and function of the heart improved."
More research is needed to discover the impact of the acute reduction in heart function. In people with existing heart problems it might exacerbate their condition -- for example aggravating heart failure symptoms like shortness of breath or increasing the risk of arrhythmias.
Dr Rayner said: "If you have heart problems, you need to check with your doctor before embarking on a very low calorie diet or fasting. People with a cardiac problem could well experience more symptoms at this early time point, so the diet should be supervised."
She added that very low calorie diets do have benefits and do not need to be avoided. "Healthy people may not notice the change in heart function in the early stages," she said. "But caution is needed in people with heart disease."
Story source: European Society of Cardiology (ESC). (2018, February 2). Crash diets can cause transient deterioration in heart function. ScienceDaily. Retrieved February 11, 2018 from www.sciencedaily.com/releases/2018/02/180202123836.htm