Here’s the ‘skinny’ on high-protein, low-carb diets

These diets are based on the idea that carbohydrates are bad because they stimulate the release of insulin, said Janice Hermann, Oklahoma State University Cooperative Extension Service nutrition education specialist.

“Historically, insulin has been associated with blood sugar, and it’s true that insulin has dramatic effects on carbohydrate metabolism,” Hermann said. “However, you must keep in mind that insulin is necessary for the normal metabolism of not only carbohydrates, but also proteins and fats. Insulin affects fat and protein metabolism almost as much as it does carbohydrate metabolism.”

High-protein, low-carbohydrate diets are being promoted as fast and easy approaches to weight loss. They involved a severe restriction of carbohydrate intake, which often results in an overall decrease in total calories.

Hermann said when carbohydrate intake is limited, the body breaks down lean body mass in an effort to provide glucose to the central nervous system.

“The body also breaks down fat in an effort to provide energy and slow the breakdown of lean body mass,” she said. “Dietary fat intake is typically increased with high protein intake, and serves as a major source of calories. Excessive breakdown of fat for energy can result in ketosis, which suppresses hunger.”

The initial rapid weight loss is the appeal of most fad diets. Low-carbohydrate diets are characterized by an initial rapid weight loss, which is primarily due to water loss. Decreased carbohydrate intake causes depletion of liver and muscle glycogen, which results in a large water loss, since about three parts of water are stored with one part of glycogen.

Limiting carbohydrate intake also decreases the ability of the kidneys to concentrate the urine, leading to additional water loss and increased excretion of sodium.

“While all of these factors combined do result in weight loss, keep in mind that it’s temporary,” Hermann said.

Excess protein intake in itself can result in increased water loss. Protein intake beyond what is needed to incorporate into new proteins is either burned for energy or converted to fat.  However, before the body can use protein for energy or convert it to fat, the nitrogen group must be removed.

“This nitrogen is converted to urea, which is removed from the body in the urine, resulting in increased water loss. In addition, the kidneys have to work harder to remove the extra nitrogen resulting from excess protein intake,” she said.

Some possible complications associated with low-carbohydrate, high-protein diets include ketosis, dehydration, electrolyte loss, calcium depletion, weakness due to inadequate dietary carbohydrate, nausea due to ketosis and possible kidney problems. Vitamins and mineral deficiencies are other problems in such unbalanced crash diet regimens.

Gout is another potential side effect, along with coronary heart disease in some individuals who stay on these types of diets for a long time if there is an increased consumption of protein foods high in fat.

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Oklahoma State University, U.S. Department of Agriculture, State and Local Governments Cooperating: The Oklahoma Cooperative Extension Service offers its programs to all eligible persons regardless of race, color, national origin, religion, gender, age, disability, or status as a veteran, and is an equal opportunity employer.
 
Trisha Gedon
Communications Specialist
Agricultural Communications Services
136 Agriculture North
Oklahoma State University
Stillwater, OK  74078
405-744-3625 (phone)
405-744-5739 (fax)
trisha.gedon@okstate.edu