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These Popular Weight Loss Diets Are Bad For Your Heart, Says Cardiologist

Steer clear of these diets to keep your heart in good shape.
MEDICALLY REVIEWED Clipboard BY Cedrina Calder

While certain diets are lauded for their dramatic weight loss effects, that doesn't necessarily mean they're good for your heart health. With 1 in every 4 deaths in the U.S. attributable to heart disease, the need to take care of your cardiovascular system through diet and lifestyle habits is critical.

Here, Dr. Elizabeth Klodas, MD, FACC, cardiologist, and founder of Step One Foods, addresses three popular weight-loss diets that could be detrimental to your heart. In conclusion, she shares which diet is the best for both your heart and overall health. Before you go, don't miss 15 Underrated Weight Loss Tips That Actually Work.

Worst diets for heart health.

Keto diet

Many saying no to carbs so he is cutting carbs and choosing a keto diet instead

The keto diet, and even the paleo and Atkins diets, fall under the same category of diets, according to Klodas. They're all high in animal protein and fat but low in carbohydrates.

There are a few points of concern here with these types of diets. First, low-carb diets have been shown to impair vascular function, meaning the arteries can't dilate properly, resulting in insufficient blood flow to the heart, the cardiologist says.

In addition, routine consumption of foods that are high in saturated fat (think bacon, butter, and cheese) can ultimately lead to high LDL (harmful) cholesterol levels—a known marker of increased heart event risk.

"I've seen especially large increases in LDL in patients following keto," she says, adding that several studies have indicated that those who follow the keto diet experience a 35% increase in their LDL levels on average.

"Not everyone has this response," she adds. "But if you are on this diet, you should have a cholesterol test."

Medifast diet

protein shake chocolate

The Medifast diet has been around since the '80s, and while this carbohydrate-controlled, low-fat diet is known to help you drop weight fast, it may not be good for your heart. With more than 40 portion-controlled and fortified meals to choose from, this calorie-restrictive diet is marketed toward people who need to lose a lot of weight and don't have time to cook or prepare their own meals.

While this may sound appealing to many, Klodas warns that a whole day's worth of meals and snacks could cause you to consume three times the recommended amount of protein. Not to mention, the meals are heavily processed.

"Medifast meals are more chemistry than food with high levels of fortification," she says, adding that the diet also isn't sustainable. "Drastic dietary change may be good for initial weight loss, but deprivations and cravings remain. Nearly every patient I've ever seen who has tried drastic dietary changes like this gains all their weight back."

Referred to as "yo-yo dieting," significant fluctuations in weight can double your risk of heart disease, Klodas says.


nutrisystem turkey ham and cheese omelet plated with cut fruit
Courtesy of Nutrisystem

Similar to the Medifast diet, the Nutrisystem diet largely consists of prepackaged, frozen meals, which can cost up to $400 a month (excluding the additional groceries you may need to prepare some of the food yourself). Klodas says the ingredient profiles of many of Nutrisystem's prepackaged meals should be subject to skepticism, since they're laden with additives, preservatives, and artificial flavors.

"There's simply more to health than just losing weight," she says. "It's not only the quantity of food that matters—quality is vitally important, too."

Best diet for heart health.

Mediterranean diet

mediterranean platter

Klodas isn't the only health expert who thinks the Mediterranean diet is great for your heart. In fact, it was the top diet in U.S. News' ranking of the best diets for overall health this year, which is created by a panel of registered dietitians, physicians, and preventive medicine specialists (just to name a few). The Mediterranean diet emphasizes whole foods, primarily fresh fruits and vegetables, legumes, and lean protein selections like fish.

And unlike these other diets, this way of eating is considered a lifestyle rather than a quick way to lose weight. "A diet high in fresh fruits and vegetables that limits sodium can be as effective as a drug in lowering blood pressure," Klodas says.

Bottom line

Overall, Klodas recommends avoiding diets in general, as many of them aren't sustainable.

"My biggest message is that you don't have to be perfect, you just have to be better," the cardiologist says, adding that the lifestyle changes you make today need to be something you can sustain—unlike those associated with crash dieting.

"Small changes, if they are the right changes, can make a huge difference in health," Klodas says. "And when you eat for heart health, you're also supporting everything else, including weight loss."

For more, be sure to check out the 14 Best Diets For Weight Loss in 2021, According to Experts.

Cheyenne Buckingham
Cheyenne Buckingham is the former news editor of Eat This, Not That! Read more about Cheyenne
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