Nutrition

November 6, 2010

How Much Protein Do You Need?

No question about it, protein is the most important macronutrient in your diet. But many people are confused as to how much protein they really need to consume. Here’s the lowdown…

If you go by the recommended dietary allowance (RDA) espoused by the Department of Agriculture, protein intake should equate to a little less than 0.8 grams per kilogram of bodyweight. The RDA, however, has a major flaw in its design: it bases protein requirements on the average couch potato. While this is fine if you want to be an average couch potato, it has little relevance if you are a hard training fitness enthusiast. In truth, those who aspire to optimize body composition require significantly more protein than what is prescribed in the RDA.

For active individuals, especially those involved in strength training regimens, studies have consistently shown optimal intake to be about 1.6 to 2.0 grams of protein per kilogram of bodyweight (roughly double the RDA). The reasons are twofold: First, during exercise, amino acids are oxidized for fuel at an accelerated rate. Depending on the intensity and duration of training, these amino acids can supply up to 10 percent of the body’s energy needs. What’s more, the stresses associated with physical activity cause an increased breakdown of body proteins, leaving the body in a catabolic state. The only way to reverse these effects and promote an anabolic environment is by consuming additional dietary protein, over and above RDA guidelines. Abide by the RDA and you’ll surely be in a negative nitrogen balance (i.e. your body is breaking down proteins at a greater rate than it’s synthesizing them).

A protein-rich diet also confers specific metabolic benefits. For one, a large percentage of calories from protein are burned off in the digestion process—a phenomenon called the thermic effect of food (TEF). Of all the macronutrients, protein has the highest thermic effect, burning off approximately 25 percent of the calories consumed. In comparison, only about 8 percent of the calories from carbs are burned off in digestion; the thermic effect of dietary fat is minimal. When the TEF is factored into a mixed meal, higher intakes of protein can as much as double post-prandial thermogenesis (i.e. the number of calories burned after eating), leaving fewer calories available to be stored as fat.

Further, protein tends to curb appetite. During its digestion, protein potentiates the secretion of a hormone called cholecystokinin (CCK), which acts to suppress the body’s hunger mechanisms. These satiety-inducing effects are pronounced, lasting several hours after a meal. And when appetite isn’t driven by hunger, food choices can more easily be made based on rationale rather than impulse. This is why studies have consistently shown that when people are left to make their own nutritional decisions (called an ad libitum diet), those who consume high amounts of protein take in significantly fewer calories than those who don’t.

A higher protein intake is especially important when you are restricting calories (i.e. the goal is weight loss). During stringent dieting, there is a tendency for your body to break down protein stores into glucose (through a process called gluconeogenesis) so that the brain and other tissues have adequate fuel. Since skeletal muscle is not necessary for sustenance (as opposed to the internal organs and other protein-based tissues), it is the primary bodily tissue to be cannibalized. The only way to counteract this occurrence is by consuming extra protein. Keeping protein intake high helps to preserve lean tissue, preventing the negative consequences of muscle wasting.

Taking all factors into account, my general recommendation is to consume approximately one gram of protein per pound of ideal bodyweight (i.e. the weight you aspire to being when you are at your leanest). This provides a margin of safety, ensuring you never fall into negative nitrogen balance. And in case you’re worried about negative health effects, rest easy. As long as you have healthy kidney function, research has debunked the claims that higher protein diets will put you on dialysis. For more info, read my article High Protein Diets: Myths, Half-truths and Outright Lies.

Stay Fit!

Brad