How trendy crash diets can damage your heart

THEY might seem like the perfect way to lose weight in a hurry.

But trendy crash diets have been found to cause sudden deterioration of the heart.

So- called ‘ meal replacement programmes’ slash daily energy intake to 600 to 800 calories, down from the recommended 2000 to 2500, and have reportedly been adopted by celebrities including Gwyneth Paltrow and Beyonce.

However, a study led by the University of Oxford found a very low calorie diet has a negative impact on heart function, as well as blood pressure and cholesterol.

The sudden drop in food intake releases fat from the body which ends up in the heart muscle.

After just one week, researchers found that people on the diet had increased their heart fat content by 44 per cent.

The dramatic deterioration in heart function was short-lived, but researchers warn there could be dangers for those with underlying cardiac problems.

The study’s lead author, Dr Jennifer Rayner, said: ‘Crash diets, also called meal replacement programmes, have become increasingly fashionable in the past few years ... But the effects on the heart have not been studied until now.’

The study included 21 obese volunteers with an average age of 52 who were put on a crash diet for eight weeks.

MRI scans were used to measure the effect of the diet on the heart and the distribution of fat in the abdomen, liver and heart muscle. It took one week for participants’ heart fat content to rise by almost 50 per cent, making it harder for the muscle to pump blood.

This is the opposite of what was expected, as the effects of weight loss should improve heart function. Explaining the results, Dr Rayner said: ‘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 ... The heart muscle prefers to choose between fat or sugar as fuel, and being swamped by fat worsens its function.’

However, she added: ‘After the acute period in which the body is adjusting to dramatic calorie restriction, the fat content and function of the heart improved.’

The diet did reduce people’s body fat by 6 per cent in just one week. Participants also saw falls in blood pressure, cholesterol and blood sugar, along with a reduction of 41 per cent in liver fat.

And after two months, participants’ heart fat content and function were better than they were before going on the diet. But the effects of such a sudden drop in heart function were unclear.

For people with heart problems, it could make their condition worse, aggravating heart failure symptoms such as shortness of breath or increasing the risk of an irregular heartbeat.

Dr Rayner said crash diets do have benefits, but she warned that those with cardiac issues should speak to a doctor before trying one.

The research, partly funded by the British Heart Foundation, was presented at CMR 2018, the meeting held by the European Society of Cardiology, in Spain.

‘Swamped by fat’