Low or Medium Carbs
Popular diets recommend different amounts of carbohydrates. At one end of the diet spectrum are the high-carb, lowfat diets—at least 60 percent carbs, with the suggested carbs being those high in fiber, such as fruits, grains and vegetables. The idea is that fat is the densest source of calories, at nine per gram, compared to the four calories per gram in carbohydrates and protein. Since most lowfat, high-carb diets are either low or moderate in protein content, however, they’re not popular with those seeking added muscle. Protein and fat positively influence the flow of anabolic hormones conducive to building muscle, such as testosterone and growth hormone. For most bodybuilders who want to lose fat, low-carb diets are the way to go.
One reason low-carb diets are effective is that they lower insulin levels. While insulin has anabolic effects in muscle, it’s also “fattening,” stimulating every known mechanism that increases bodyfat levels. Carbs stimulate more insulin than protein or fat.
Even among low-carb advocates, however, debate rages about how many carbs are required. Popular diets such as Atkins and Protein Power recommend beginning with an ultralow level of carbs, averaging 30 grams a day or fewer. The idea is to bring down the resting insulin level. Since most people with excess bodyfat have a higher-than-normal insulin response to meals and at rest, lowering insulin kick-starts fat loss. The initial rapid weight loss on an ultralow-carb diet is mostly water, but it provides a psychological impetus to staying on the diet.
Other diet experts recommend a moderate intake of carbs. Biochemist Barry Sears suggests that 40 percent of your daily calories should be carbs. His Zone diet mandates only low-glycemic-index carbs, which are those higher in fiber.
Which type of diet most effectively curtails the hunger demon? A recent study compared the effects of an ultralow-carb diet and a moderate-carb diet similar to the Zone diet. Seventeen obese men followed one of two types of diets: 1) a low-carb, or ketogenic, diet containing only 4 percent carbs or 2) a moderate-carb diet containing 35 percent carbs. Both diets featured 30 percent protein. The men were permitted to eat as much as they wanted on either diet, as long as they stayed within the parameters of the nutrient content.
The subjects ate fewer calories on the lower-carb diet than on the higher-carb one. They were also less hungry, explaining why they ate less. The ketogenic diet is so named because it favors a higher level of ketones in the blood. Ketones are metabolic by-products of fat metabolism that can serve as an alternative energy source when sufficient carbs aren’t available. Both muscles and brain can easily use ketones as an energy source. Animal studies show that an abundance of ketones exerts an appetite-supressing effect on brain chemistry.
A frequent criticism of low-carb diets is that dieters eat less because the foods aren’t palatable. That wasn’t the case with this study, which featured a wide variety of flavorful foods.
The moderate-carb diet proved superior in its effects on low-density-lipoprotein cholesterol, which is linked to various cardiovascular diseases. On the other hand, a low-carb diet is an effective way to lower blood triglycerides, which are a precursor of LDL synthesis in the liver. In addition, a recent study showed that when men followed low-carb diets and also ate eggs (which are high in cholesterol), they experienced significant increases in high-density-lipoprotein cholesterol, which offers protective effects against cardiovascular disease.
1 Johnstone, A.M., et al. (2008). Effects of a high protein ketogenic diet on hunger, appetite, and weight loss in obese men feeding ad libitum. Am J Clin Nutr. 87:44-55.
2 Mutungi, G., et al. (2008). Dietary cholesterol from eggs increases plasma HDL cholesterol in overweight men consuming a carbohydrate-restricted diet. J Nutr. 138:272-276.