By Fariha Fawziah
Who else has that particular friend who will occasionally run and restrict themselves to 700 calories a day for a week so they can lose weight fast? Maybe even *you* are sometimes that friend. A “crash diet” is a weight-loss diet—during which one consumes 1,000 or even as low as 500 calories per day—with the goal of achieving rapid results.
Crash diets are known to have many negative health effects. They can slow your metabolism (making it harder to burn calories), thereby increasing the chance of burning your muscles for energy instead. They can make you hungry all the time, causing you to be more cranky due to changes in neural networks and brain activity. You might also become physically and mentally exhausted.
Furthermore, you could miss out on essential nutrients such as protein, fiber, amino acids, calcium, iron, and vitamin B12. Without these, your body, specifically, your bones, cognitive function, and blood cells may suffer.
Research isn’t as clear when it comes to predicting what happens after your crash diet. Here’s some of the things that could happen: your insulin sensitivity (and risk of diabetes) might be impacted; fat might come back faster than muscle does; and your sympathetic nervous system may become more inactive—meaning you might feel colder and your heart rate may be slower than usual. There might even be a drop in blood pressure that could cause you to pass out.
According to new research, crash diets can cause a transitory deterioration in heart function. Not much research had been done on its effects on the heart until now. Researchers used magnetic resonance imaging (MRI) to investigate the impact of a very low-calorie diet on heart function and the distribution of fat in the abdomen, liver, and heart muscle.
The study included 21 obese volunteers (fifteen were women and and six were men). The average age was 52 years, and the average body mass index (BMI) was 37 kg/m2. Participants consumed a very low calorie diet of 600 to 800 calories per day for eight weeks.
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. On the other hand, there were also significant improvements in insulin resistance, fasting total cholesterol, triglycerides, glucose, and blood pressure, due to total body fat.
By eight weeks, the heart-fat function had improved more than what they initially started with, and all other measurements—including body fat and cholesterol—were continuing to improve.
Dr. Jennifer Rayner, who is the lead author of the study, and a clinical research fellow at Oxford Centre for Magnetic Resonance, says: “The metabolic improvements with a very low calorie diet, such as a reduction in liver fat and reversal of diabetes, would be expected to improve heart function. Instead, heart function got worse in the first week before starting to improve.”
In conclusion, more research is needed to truly discover the reduction in heart function from crash diets. Patients with heart disease should seek medical advice before adopting a very low calorie diet.