Crash Diets Temporarily Impair Heart Function
Severe calorie restriction improves various metabolic measurements, but causes a buildup of heart fat.
Very low-calorie diets are becoming increasingly popular as an effective weight-loss strategy that rapidly reduces liver fat and diabetes. But according to new findings presented Feb. 2 at the CMR 2018 meeting in Barcelona, these metabolic improvements come with a dark side: a significant buildup of heart fat and a decline in cardiac function.
In the study, 21 obese volunteers went on a very low-calorie diet for eight weeks, consuming only 600 to 800 kilocalories per day. The researchers used a combination of MRI, 1H-MR spectroscopy and echocardiography to assess abdominal visceral and liver fat, left ventricle structure and function, myocardial triglyceride content and diastolic function.
After only one week of dieting, total body fat, visceral fat and liver fat dropped by an average of 6 percent, 11 percent and 42 percent, respectively. These effects were accompanied by marked and rapid improvements in insulin resistance, fasting total cholesterol, triglycerides and glucose.
Despite these metabolic benefits, myocardial triglyceride content rose by 44 percent and was associated with reductions in both systolic function and diastolic function. According to the researchers, 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. But by eight weeks, both myocardial triglyceride content and cardiac function returned to normal as other metabolic measurements continued to improve.
Even though the negative effects of severe calorie restriction were temporary, the findings suggest that people with heart problems should talk with their doctor before embarking on a very low-calorie diet.
CMR 2018 is a joint EuroCMR/SCMR meeting organized by the European Association of Cardiovascular Imaging, a registered branch of the European Society of Cardiology, and the Society for Cardiovascular Magnetic Resonance.