Low-Carb and Low-Calorie Diets: What You Need to Know

Low-carb and low-calorie diets may lead to weight loss, but any diet that's extreme in nature can cause negative side effects.
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Low-carb and low-calorie diets have become so popular that names like Atkins and keto have become part of everyday lexicon. But can these diets lead to heart palpitations, low blood pressure and other dangerous side effects? The short answer is yes.

Carbs and Calories Explained

Certain foods are high in carbohydrates, including bread, rice, pasta, sugar, sweets, flour and fruit, explains Sharon Zarabi, RD, CDN, bariatric program director at Lenox Hill Hospital, New York City.

"Calories are found in macronutrients — what we know as carbohydrates, fats and proteins," Zarabi says. "Fats, carbs and protein all contain different amounts of calories per gram, and also affect our metabolism."

Low-carb diets are those that lower your intake of these foods. Examples include the Atkins diet and the ketogenic diet. A low-calorie diet is one in which any nutrient — whether carbohydrates or protein — is reduced.

"Eating more than we actually require ultimately leads to excess energy, and the body will then store this as 'excess body fat,'" Zarabi says. "Simply put, excess calories in any form will cause extra adipose tissue or weight gain."

How These Diets Work

The main benefit of a low-carb diet is quick weight loss, according to Zarabi. "Carbohydrates get stored with water, so when you eat less, you have less water weight," she says. "That is why anyone who goes on what we know today as a ketogenic diet or low-carb diet loses weight quickly."

But Zarabi cautions that we also need carbohydrates to fuel the brain, improve sports performance and provide fiber, which helps maintain healthy gut transit. "Fiber which helps keep us full and influences bowel function is found in complex carbohydrates," she says. "Vegetables contain a small amount of carbohydrates, so it's important to include these high-fiber carbohydrates in your diet for long-term health."

Eating fewer calories can be problematic as well if you cut out the wrong calories. "Eating less calories from the wrong foods can leave you hungry!" Zarabi says. "Not all calories are created equal. Eating less calories from protein will have a very different impact on our hormones and metabolism than a diet low in carbohydrates."

What About Side Effects?

But can a low-carb or low-calorie diet cause side effects like heart palpitations? Indeed it can.

"Any diet that is extreme in nature can have side effects," according to Zarabi. "This may include heart palpitations, lower blood sugars and lower blood pressure because your body is receiving less nutrients, and normal bodily functions are impaired."

If you're determined to follow one of these diets, understanding where the calories are coming from will ultimately affect your long-term success and reduce hunger. Being hungry all the time is not the best way to lose weight, Zarabi points out, which is ultimately the reason why diets often fail.

"When following a low-calorie diet with healthy fats, lean sources of protein and high-fiber carbohydrates, you have the key to long-term success," she says.

Read more:Negative Side Effects of a Low-Carb Diet

Healthy Eating

In addition to Zarabi's suggestion to eat a low-calorie diet with healthy fats, lean protein and high-fiber carbs, you can also consider the recommendations for carbohydrates from the American Heart Association:

  • Keep to a minimum foods that are high in processed, refined simple sugars because they provide calories but are not nutritious.
  • Consume more fruits and vegetables, as they are good sources of complex carbohydrates.
  • Rice, breads and cereals should be of the whole-grain variety.
  • Also make sure to include legumes like beans, dried peas and lentils in your diet.

When it comes to calories, most people don't need to count them every day, according to the Academy of Nutrition and Dietetics.

To strike the right balance in terms of food intake, the academy recommends paying close attention to "personal cues" that tell you you're hungry or full. For example, if you feel weak, irritable or shaky, these can be signs of hunger. A good way to determine how full you are is to pace yourself — take a break halfway through your meal, which will allow your body to digest, before eating the second half of the meal.

Read more:10 Foods Under 10 Calories You Should Be Eating More Of

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