Crash diets: MRI study shows why they’re bad for the heart | Lifestyle.INQ

OCTOBER 27, 2022

I’ve always had misgivings about anything achieved quickly—get-rich schemes, whirlwind romances and lose-weight-fast prescriptions.

A scientific paper presented last week at the 2018 Cardiovascular Magnetic Resonance (CMR) Congress in Barcelona, Spain, warns crash dieters that rapid weight loss may be associated with deterioration of heart function.

This was noted even in people with no known heart problems. Imagine how disastrous it would be for those with cardiovascular disease.

Normal hearts can likely handle this temporary deterioration in heart function, but for those with diseased hearts, this can be the tipping point that could cause heart failure and irregular heartbeats leading to sudden cardiac death.

A crash diet is a way to lose five to 20 pounds in a week. This is resorted to by artists and performers, brides and grooms, athletes like boxers, and practically everyone who finds herself or himself several pounds overweight before an important event.

The event could be an upcoming party, date, wedding, performance, photo shoot, weigh-in for boxers, among other occasions.

Because of the short period to lose weight, one resorts to a drastic lowering of caloric intake, as low as 600 calories per day. The basic formula for weight loss is to take in less calories than what the body can burn, but if one drastically reduces those calories by half or less, the body literally starves.

Depending on height and ideal weight, the average adult needs around 1,300 to 1,500 calories just to maintain basal metabolism and function.

Most hardworking organ

Considering that the heart is the most hardworking organ in the body, working 24/7 nonstop—constantly beating more than 100,000 times daily to pump circulation to each and every cell of the body—
one can imagine what happens to this vital organ if it’s not fed well. It will certainly weaken and can go into failure.

It’s amazing how the heart does its job without people realizing exactly what that job is. It’s like doing push-ups 100,000 times daily nonstop
—with just a fraction of a second’s break in between.

Dr. Jennifer Rayner, the study’s lead author from Oxford Centre for Magnetic Resonance at the University of Oxford in the United Kingdom, warned those frequently resorting to this diet about its potential effects on the heart. Although previous studies showed that very low calorie content of 600 to 800 kcal per day is effective for losing weight, reducing blood pressure and reducing blood sugar, the effects on the heart—
though transient—are a cause for concern.

The effect is likely to be temporary and may not matter much for those with strong, healthy hearts. But for those with reduced or marginal heart function, crash diets can push one off the cliff to a catastrophic end.

In the study, the investigators used magnetic resonance imaging (MRI), a very reliable diagnostic exam to detect malfunctioning of the heart and other organs, to evaluate the impact of a very low calorie diet on heart function and the distribution of fat in the abdomen, liver and heart muscle.

Recruited as subjects were 21 obese volunteers, six men and 15 women with an average age of 52 and average body mass index (BMI) of 37 kg/m². They consumed a very low calorie diet of 600 to 800 kcal per day for eight weeks. The MRI was done upon enrollment in the study, and after one and eight weeks.

After one week, as expected, there was a significant reduction in total body fat, abdominal fat and liver fat, accompanied by significant improvements in insulin resistance which causes diabetes, fasting total cholesterol, triglycerides, glucose and blood pressure.

Deterioration in function

However, despite the improvements noted in these metabolic parameters, heart fat content increased by 44 percent—a negative sign of how the heart is affected by the diet. This was associated with a deterioration in heart function—a diminution in the heart’s ability to pump blood (ejection fraction) into the circulation to supply all cells of the body with the needed oxygen and nutrients.

Even the researchers were surprised by this seeming paradox.

“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,” said Dr. Rayner.

To be fair to the crash diet, though, after eight weeks, there was improvement in heart fat content and function, and all other measurements, including body fat and cholesterol, continued to improve.

Dr. Rayner explained that a sudden reduction in calorie intake to 600-800 kcal per day causes fat to be released from different parts of the body into the blood—similar to the withdrawal of savings when one’s income is no longer enough to meet the living expenses.

This sudden withdrawal leads to excess deposits of fats on the heart muscle, which uses either fat or sugar as fuel. Being swamped with an excessive amount of “unprocessed” fat worsens 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,” she reported.

Because of the small number of participants, this study can’t be conclusive, and more research is needed to find out the long-term impact of the reduction in heart function after a week of crash dieting.

“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 point, so the diet should be supervised,” Dr. Rayner advised.

So, the bottom line is that crash diets may not really be risky for everyone, but it’s also not safe for everyone. One’s heart condition must be assessed first, to see if it can handle the undue stress it is put under in the initial stages of the diet.

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