The crash diet, which is also known as the meal replacement program, is one of the most popular methods used by the adult population to reduce weight.
Cutting down the daily calorie intake to half or less is believed to be an effective way to fight obesity mainly because it leads to decrease in abdominal fat.
However, a study by a group of researchers from the University of Oxford has warned about the side effects of the crash diet on the body. According to the study, a sudden decrease in calorie intake may harm the heart.
The lead researcher of the study, Dr Jennifer Rayner, has said that meal replacement programs can lead to an increase in levels of heart fat. It might eventually lead to breathlessness and irregular beating.
So, a person with heart diseases should be extra cautious before adopting such methods to reduce weight or else they may suffer from cardiac problems in the future, said the researcher.
"Crash diets, also called meal replacement programmes, have become increasingly fashionable in the past few years. The heart muscle prefers to choose between fat or sugar as fuel and being swamped by fat worsens its function. If you have heart problems, you need to check with your doctor before embarking on a very low-calorie diet or fasting," Mail Online quoted her.
"People with a cardiac problem could well experience more symptoms at this early time point, so the diet should be supervised," the researcher said, adding, "Otherwise healthy people may not notice the change in heart function in the early stage."
However, it may also be difficult to lose weight by not following a proper diet. A study on the connection between weight loss and diet by a group of researchers from the Bangor University shows that regular exercise without the reduction of calorie intake might not have any significant on weight loss.
"To be effective, exercise training for weight loss needs to be integrated into a lifestyle approach to weight loss, including exercise combined with diet," lead researcher Dr Hans-Peter Kubis said.
"Seeing no change on [the] scales may be enough to make people give up on their exercise training, not realising that they have actually improved their body by gaining muscle mass," he added.