Maybe you want to lose weight more easily. Maybe you’re trying to build muscle or boost your metabolism. Whatever the reason, you’ve decided to try one of the high-protein diets that have become so popular in recent years. After all, what’s the harm?

How much protein do you need?

Protein is, of course, an essential nutrient. In fact, it’s one of the three major macronutrients, along with carbohydrates and fat—the components of food that the body needs for energy and to maintain its structure and systems. Ideally, according to Corey Tolbert, RD, LD, a licensed and registered dietitian at Cancer Wellness at Piedmont, you need .8 grams of protein per kilogram of your ideal body weight. That’s about 51 grams of protein a day for a person weighing 140 pounds.

Why go on a high-protein diet?

Consuming high amounts of protein is the key to ketogenic and other high-protein diets. And they do work to help you lose weight. Unfortunately, they also cause heart problems, kidney damage and bad breath. “You do lose weight,” Tolbert says, “but then you gain it back, plus. It’s not realistic or sustainable over time.”

What’s so bad about eating too much protein? First, for most people, it means eating too much saturated fat. Eating large amounts of beef, pork, bacon and other processed meats can lead to heart disease by driving up your cholesterol, especially the more harmful LDL cholesterol, which prompts blockages to form in your arteries and elsewhere in the body. Second, eating too much animal protein causes kidney stones and other damage. It creates more acid and toxins in the body, putting more pressure on the kidneys to filter and process all those substances. It also makes you more thirsty, which means you want to drink more, and “that’s hard on the kidneys, too,” Tolbert notes. “If your kidneys are always in overdrive, that causes problems.”

One more unpleasant side effect of high-protein diets? They cause bad breath. When your body turns to stored fat for energy, it enters a metabolic state called ketosis, in which a high concentration of ketones is in the blood. Those ketones smell awful and can’t be masked by brushing or flossing.

What about carbs?

The flip side of many high-protein diets is that they discourage people from eating carbohydrates. But if you decrease your carb intake, “you’re depriving your body of its main energy source,” according to Tolbert. Carbs, which are one of the three major micronutrients, are a natural source of glucose, and glucose is important to healthy functioning. It’s the primary source of energy for every cell in your body, and it’s the only energy that powers your brain. In fact, it’s the only one that crosses the blood-brain barrier. Brain functions such as thinking, memory, and learning are closely linked to glucose levels.

If you really want to lose weight, boost your metabolism or build lean muscle, talk to your doctor first. You can discuss what methods, tips and tricks will work for you. To make an appointment with a Piedmont physician and save time, book online.