High-protein, low-carb diets may not be safe in the long term

May 15, 2019

Q. I've been on a diet high in proteins and low in carbohydrates for several weeks now and I've lost weight on it. What do you think of this type of diet?

These diets can bring a quick drop in weight because eliminating carbohydrates causes a loss of body fluids. And, high-protein diets cause substances called “ketones” to be released into the bloodstream. The ketones make dieting easier by lowering appetite.

I tried one of these diets and it worked. But I didn't feel quite right eating so many high-protein dishes while avoiding carb foods such as my favorite – bread. I noticed a diminished appetite. However, I also got constipated. I quit and went back to watching calories.

I've always been skeptical about any diet that is unbalanced. Logic tells me that I must be doing something bad to my body. I don't think it's safe to lean in one direction at the dining room table.

“For most healthy people, a high-protein diet generally isn't harmful if followed for a short time, such as three to four months, and may help with weight loss,” said Katherine Zeratsky, a dietitian at the Mayo Clinic. “However, the risks of using a high-protein diet – usually with carbohydrate restriction – for the long term are still being studied. Several health problems may result if a high-protein diet is followed for an extended time.”

Here are some problems:

• Some high-protein diets don't provide enough fiber. This can can cause constipation and intestinal inflammation. This may also increase the risk for cancer.

• Many of these diets include a lot of red meat and fat, which can increase your risk of heart disease.

• A protein-packed diet may cause liver or kidney problems.

“If you want to follow a high-protein diet,” Zeratsky said, “do so only as a short-term weight-loss aid. Also, choose your protein wisely. Good choices include fish, skinless chicken, lean beef, pork and low-fat dairy products. Choose carbs that are high in fiber, such as whole grains and nutrient-dense vegetables and fruit. And if you have kidney disease, liver disease or diabetes, or if you're taking medication for a chronic health condition, talk to your doctor before starting a high-protein diet.”

The American Heart Association doesn't recommend high-protein diets for weight loss because “people who stay on these diets very long may not get enough vitamins and minerals, and face other potential health risks.” The AHA also asserts that more research is needed on the effectiveness of these diets for long-term weight loss.

Most Americans already eat more protein than their bodies need. The AHA urges dieting adults to eat no more than 35 percent of total daily calories from fat, less than 7 percent of total daily calories from saturated fat, and less than 1 percent of total daily calories from trans fat. Trans fat raises your "bad" (LDL) cholesterol and lowers your "good" (HDL) cholesterol.

On most high-protein diets, meeting these AHA goals is impossible.

The American Heart Association urges people to use safe and proven methods for losing and maintaining weight. Dieters should pay attention to calories and enjoy healthy, nutritionally balanced meals. The AHA says a healthy diet includes a variety of foods, and is rich in fresh fruits and vegetables.

[In my next column, I'll detail the role of protein.]

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